Orphenadrine

skeletal muscle relaxant, ether chemically close to the antihistamines, anticholinergic [7][8]

Also sold as Norflex.

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Findings for this medication

Research about this medication, graded for how strongly each finding can be attributed to it. Nothing here describes your own levels.

Orphenadrine has no documented classical depletion machinery. The three label texts read give no pharmacokinetic section, no CYP statement and no vitamin, mineral, antacid or food interaction [1][2][3]. Outside the labels: hepatic N-demethylation to active metabolites with glucuronides and an N-oxide among eight urinary products [9]; a single-dose half-life of 13.2 to 20.1 hours that lengthens 2 to 3 fold with repeated dosing, which the authors attribute to product inhibition by N-demethylorphenadrine [13]; CYP2B induction in rats [15]; and a shorter antipyrine half-life when orphenadrine was added to chlorpromazine in patients [14]. Of the nine mechanism classes screened, enzyme induction (class B) and a possible change in intake from dry mouth (class H) are present, and neither was linked to a measured nutrient. Red and orange tiers are empty. Six entries are yellow and five are ungraded, and no yellow entry is a nutrient deficiency.

skeletal muscle relaxant, ether chemically close to the antihistamines, anticholinergic [7][8] · ATC: M03BC01 (orphenadrine citrate; also listed as N04AB02 in a general reference) [7][8] · also sold as Norflex and Norgesic (with aspirin and caffeine) and Disipal (hydrochloride); many generics [8] · reviewed 2026-10-07. This describes research about the medication. It does not say anything about your own levels or health.

How to read the evidence grades

These colours describe how strongly a finding can be attributed to the medication in the research. They are not a severity score and they say nothing about your own health.

Grades describe how strongly a finding can be attributed to Orphenadrine in the research — not how common it is, how serious it would be, and not anything about you personally.

Red — Severe: Two or more independent Tier A sources, this drug in the cohort, the nutrient directly measured, consistent direction, clinically meaningful magnitude, a named mechanism, no substantial contradicting Tier A evidence.
Orange — Moderate: At least one Tier A source with this drug in the cohort showing a real but bounded deficit: an exposure window, a subgroup, low frequency, or a functional rather than circulating deficit.
Yellow — Low: Mechanistic plausibility only (Tier B), or class extrapolation (Tier C) with no drug-specific human status data; also used for context flags and interactions running the other direction.
Not graded — disclosed evidence gap: Nothing has been measured here, so this finding cannot be graded. That does not establish either safety or harm, and it is not the same as a White result.Source definition: Not gradeable under the rules above because nothing has been measured. Published as a documented gap, never as reassurance that there is no effect.

What the research found

Dietary intake: labeled dry mouth, nausea, vomiting and constipation; intake not measured (context flag)

Yellow — Low

See study details

Dryness of the mouth is the labeled first adverse effect of orphenadrine, with nausea, vomiting, gastric irritation and constipation also listed, and a randomized trial in cirrhosis reported dry mouth, drowsiness and nausea as the minimal adverse effects; no study measured food intake, appetite, weight or nutrient intake in orphenadrine users.

Full detail and limits

What the grade means here: Mechanistic plausibility only (Tier B), or class extrapolation (Tier C) with no drug-specific human status data; also used for context flags and interactions running the other direction. Yellow

Limits on what this shows

Key null findings: PubMed listing orphenadrine dry mouth returned 4 records, all reporting dry mouth as an adverse effect, none measuring intake or weight [27]. Orphenadrine saliva and orphenadrine xerostomia queries were refused (HTTP 429) and not retried. No effect of orphenadrine on dental health, taste or appetite was found.
At-risk subgroups: Older adults (label: occasional mental confusion in elderly patients) and people with cirrhosis were the studied groups; no subgroup was shown to eat less.

Direction

Possible reduced intake through an anticholinergic effect (mechanism class H), unmeasured. A change in eating is not a deficiency finding and nothing here implies that intake should be raised or lowered by supplements (Hard Rule 2).

Regulatory status

Label text read: "Dryness of the mouth is usually the first adverse effect to appear"; with higher doses effects include nausea, vomiting, constipation, drowsiness and gastric irritation; "These adverse reactions can usually be eliminated by reduction in dosage" [1]; the dry mouth, nausea, vomiting and constipation wording is in [1] and the dry mouth wording in [3]. The injection label states that adverse reactions "are mainly due to the mild anticholinergic action of orphenadrine, and are usually associated with higher dosage" [5].

Population evidence

Abd-Elsalam et al. (Eur J Gastroenterol Hepatol; 2019 per OpenAlex, 2020 per PubMed listing): randomized trial in cirrhotic patients with three or more cramps per week, 124 patients, 62 orphenadrine and 62 placebo, follow-up 2 weeks after therapy; cramps improved versus placebo at 1 month; adverse effects were minimal and included dry mouth, drowsiness and nausea (OpenAlex abstract; no dose, duration, frequencies or laboratory values in the abstract) [20]. A 2018 pilot in cirrhosis and a 1998 diclofenac and orphenadrine infusion study list dry mouth among mild effects (PubMed listing gists only; not opened) [28].

Mechanism

Named: antimuscarinic reduction of salivary secretion with gastrointestinal effects, per the label statement that the adverse reactions are anticholinergic in origin [5].

Counter-evidence held on record

Counter-evidence and limits Adverse-effect frequencies in the abstract read are qualitative. Confounding by indication is presumed: acute pain, immobility and co-medication can themselves change appetite. The trial population has cirrhosis, which independently affects nutrition. Framing caution This is a labeled side effect, not a nutrient deficiency, and it is not a reason to take any supplement. Persistent dry mouth is a matter for a prescriber or pharmacist.

Hemolysis and G6PD deficiency

Not graded — disclosed evidence gap

See study details

No evidence was retrieved that orphenadrine causes hemolysis or is a hazard in glucose-6-phosphate dehydrogenase deficiency.

Full detail and limits

What the grade means here: Nothing has been measured here, so this finding cannot be graded. That does not establish either safety or harm, and it is not the same as a White result. Ungraded

Limits on what this shows

Why no grade: Dual condition met: no Tier B or C evidence of hemolysis with orphenadrine was found, and no circulating claim that orphenadrine is a G6PD hazard was found. Not a finding of safety.

What was searched

PubMed listing orphenadrine AND (hemolysis OR G6PD): 1 record, a 1968 erythrocyte anti-inflammatory assay (Brown and Mackey) whose abstract, opened through OpenAlex, concerns steroids, indomethacin, fenamates, salicylates, DMSO and ethanol and reports no orphenadrine result, so it supports nothing [23]. PubMed listing orphenadrine glucose-6-phosphate dehydrogenase returned a 404 page [27]. The Wikipedia G6PD deficiency page does not mention orphenadrine and names primaquine, tafenoquine, dapsone, methylene blue, pegloticase, rasburicase and toluidine among agents to avoid [24]. None of the three orphenadrine labels mentions G6PD or hemolysis, and the summary of the Norgesic combination label did not mention G6PD either [1][2][3][6]. Published G6PD safe-drug and unsafe-drug lists were not retrieved. Repair re-check 2026-10-07: PubMed listing orphenadrine hemolytic was refused (HTTP 429) on four attempts spaced several minutes apart and never returned records; curated G6PD drug lists remain unsearched. PubChem pug_view Drug Warnings section for orphenadrine (CID 4601), opened on the repair pass: contraindications (acute-angle closure glaucoma, myasthenia gravis) and cautions (GI obstruction, urinary retention, tachycardia) only, no mention of hemolysis or G6PD [29].

Channel outcomes

PubMed HTML search listings (format=pubmed) opened intermittently on 2026-10-07 through a summarizing fetch tool; the shared fetch proxy returned HTTP 429 for many calls, which were not retried on the same page; a 404 page was read as the PubMed no-match response and was not independently confirmed; one multi-term boolean query returned PubMed's generic trending-articles page and was discarded. OpenAlex single-record lookups, Springer, Wikipedia, PubChem, the WHO ATC index and DailyMed label pages opened; OpenAlex and Crossref search endpoints and Europe PMC were refused (HTTP 429) and not retried; web search had exhausted its shared budget and returned nothing; PubMed Central, NCBI Bookshelf and ScienceDirect were not used or were disallowed. Details in Sources.

Gap type

Genuine gap for orphenadrine on the channels that opened; tooling-limited for curated G6PD drug lists, which could not be searched (Crossref and web search unavailable). The aspirin component of the combination was not researched, because the combination is a note only.

Hyponatremia (sodium)

Not graded — disclosed evidence gap

See study details

No evidence was retrieved that orphenadrine causes hyponatremia, SIADH or any serum sodium change.

Full detail and limits

What the grade means here: Nothing has been measured here, so this finding cannot be graded. That does not establish either safety or harm, and it is not the same as a White result. Ungraded

Limits on what this shows

Why no grade: Dual condition met: no Tier B or C evidence and no circulating hyponatremia claim for orphenadrine was found. Not a finding of safety.

What was searched

PubMed listing orphenadrine hyponatremia returned a 404 page (no-match response) [27]. PubMed listing orphenadrine sodium returned 10 of 33 records, all on sodium channel blockade, saline compatibility or analytical methods, none on serum sodium [27]. The three labels read list no sodium or fluid effect; the injection label names sodium metabisulfite 2 mg per 2 mL as an excipient with a sulfite allergy warning, which is not an electrolyte finding [3]. The Wikipedia hyponatremia page does not mention orphenadrine, muscle relaxants or anticholinergics [25]. The SIADH wording query was refused (HTTP 429) and not run. Repair re-check 2026-10-07: PubMed listing orphenadrine SIADH returned a 404 page (no-match response, not independently confirmed); orphenadrine hyponatraemia (British spelling) was refused (HTTP 429); web search budget was exhausted so no case-report search was possible. PubChem pug_view Drug Warnings section for orphenadrine (CID 4601), opened on the repair pass: contraindications (acute-angle closure glaucoma, myasthenia gravis) and cautions (GI obstruction, urinary retention, tachycardia) only, no mention of hyponatremia or sodium [29].

Channel outcomes

Gap type

Genuine gap on the PubMed channel that opened; tooling-limited for case-report databases and secondary search. If a signal were found it would run in the dilution or retention direction and the caution would be that supplementation is not the remedy (Hard Rule 5).

Vitamin D and other vitamins (hepatic enzyme induction route)

Not graded — disclosed evidence gap

See study details

Orphenadrine induces hepatic enzymes in rodents and shortened antipyrine half-life in patients, but no study measured any vitamin level in orphenadrine users.

Full detail and limits

What the grade means here: Nothing has been measured here, so this finding cannot be graded. That does not establish either safety or harm, and it is not the same as a White result. Ungraded

Limits on what this shows

Why no grade: Dual condition met for what was retrieved: no Tier B or C source linking orphenadrine to a vitamin level, and no circulating vitamin claim found. The drug's enzyme induction is itself not a nutrient finding (Hard Rule 2). Not a finding of safety.

What was searched

Mechanism class B (accelerated catabolism through hepatic enzyme induction) is present for this drug: CYP2B induction in rats [15]; induction in young but not older rats per an HSDB excerpt quoting a 1976 textbook [11]; shorter antipyrine half-life when orphenadrine was added to chlorpromazine in patients [14]; the labels are silent on CYPs [1][2][3]. Because the mechanism is present, nutrients cleared by induced enzymes were carried forward. The link from enzyme induction to vitamin D or other vitamins is background knowledge and was not retrieved in this review. PubMed listing orphenadrine vitamin returned 9 records: co-formulations with vitamins B6, B12 and C, cramp and analytical papers, none measuring a vitamin level [27]. No enzyme-inducer-class vitamin study was retrieved. Repair re-check 2026-10-07: PubMed listing orphenadrine ascorbic acid returned 2 records, both 1969 Turkish thin-layer chromatography assay papers for a quinine, o-ethoxybenzamide, ascorbic acid and orphenadrine combination, with no vitamin level measured; orphenadrine vitamin D returned 1 record, a 2022 systematic review of cramp treatments in cirrhosis in which orphenadrine and vitamin D are separate treatments (listing gist only, not opened, no vitamin level in orphenadrine users) [27]. The enzyme-inducer class angle was still not searched.

Channel outcomes

Gap type

Genuine gap for orphenadrine itself (no vitamin measurement exists in the listings read); tooling-limited for the class-level enzyme inducer angle, which was not searched because the fetch budget was throttled. A later review should search that angle before any grade is assigned.

The five body-system areas

Each finding is counted once, in a single area. Where a study is mentioned in a second area it is context only.

Mitochondrial Burden

Each finding below is counted once, in this area only.

Mitochondrial burden: reverse direction, HIF-1α and TFAM expression in rat ischemic brain only

Yellow — Low

See study details

In rats after experimental stroke, orphenadrine treatment was reported to preserve mitochondrial function as judged by HIF-1α and TFAM expression; no study measured mitochondrial structure, respiration, membrane potential or toxicity, and there are no human data.

Full detail and limits

Limits on what this shows

Key null findings: PubMed listing orphenadrine mitochondrial returned 2 records: [17] and a 1999 Neuropharmacology paper on glutamate neurotoxicity that was seen by title only [27][28]. No study of orphenadrine on isolated mitochondria, electron transport or membrane potential was found. No mitochondrial toxicity statement appears in the labels [1][2][3].
At-risk subgroups: None identified.

Direction

Reverse (protective-looking in an injury model). Not a burden finding and not a depletion finding.

Regulatory status

No mitochondrial content in the label texts read [1][2][3].

Population evidence

None in humans. Balhara et al. 2026: rat middle cerebral artery occlusion, orphenadrine 10 and 30 mg/kg intraperitoneally daily for 21 days; mitochondrial function was assessed through HIF-1α and TFAM expression, and the authors conclude orphenadrine acts through "antioxidative, anti-inflammatory, and mitochondrial preservation mechanisms in ischemic stroke" (summary of the PubMed record through a summarizing fetch tool; the direction of change for each gene was not stated in the summary; full text not opened) [17].

Mechanism

Named only in the authors' framing: multi-target neuroprotection with TFAM and HIF-1α as mitochondrial readouts [17]. No direct mitochondrial target was reported in the record read.

Counter-evidence held on record

Counter-evidence and limits Tier B, one animal study, expression of two genes as a proxy for mitochondrial function, measured against an ischemic insult rather than baseline. The same study underlies the Oxidative stress entry (see Overlap map). The sibling muscle relaxant dossiers were not used: orphenadrine is not in any of their cohorts and no mitochondrial finding is carried over. Framing caution Do not present orphenadrine as protecting mitochondria or as damaging them. There is one rodent expression finding and nothing in people.

Oxidative Stress

Each finding below is counted once, in this area only.

Oxidative stress: opposing rodent signals, lower malondialdehyde after experimental stroke versus oxidative-stress gene expression in a rat liver tumor-promotion model

Yellow — Low

See study details

In rats, orphenadrine lowered malondialdehyde and nitrite and raised glutathione and catalase after experimental stroke, while in a two-stage rat liver carcinogenesis model dietary orphenadrine raised expression of oxidative stress markers alongside CYP2B induction and CAR activation; no study measured oxidative stress, glutathione or antioxidant capacity in people taking orphenadrine.

Full detail, limits and 1 references

Limits on what this shows

Key null findings: No malondialdehyde, glutathione, superoxide dismutase, total antioxidant capacity or reactive oxygen species measurement in orphenadrine-treated humans was found. PubMed listing orphenadrine oxidative (10 records on 2026-10-07): the records on biology were [15][16][17], a human chlorpromazine interaction paper [14], and older cytochrome P-450 spectral and inhibition papers by title only; the rest were analytical or environmental chemistry [27][28]. The nefopam in vivo glutathione null in [16] is not orphenadrine evidence.
At-risk subgroups: None identified.

Direction

Mixed and unresolved. Reverse-direction signal: improved redox markers in an injury model [17]. Burden-direction signal: oxidative stress markers up in liver after exposure in a promotion model [15]. Neither is a depletion finding, neither was measured in a person, and the second is a rodent toxicology result tied to enzyme induction (Hard Rule 2: the drug's own toxicity is not a nutrient deficiency).

Regulatory status

No oxidative or antioxidant content in the three label texts read [1][2][3].

Population evidence

None in humans. Tier B, orphenadrine itself in every study. Balhara et al. 2026 (Toxicol Appl Pharmacol 510:117757): male Sprague-Dawley rats with middle cerebral artery occlusion, orphenadrine 10 and 30 mg/kg intraperitoneally from 1 hour after reperfusion, daily for 21 days; malondialdehyde and nitrite fell and glutathione and catalase rose (summary of the PubMed record through a summarizing fetch tool; OpenAlex had no abstract) [17]. Morita et al. 2013 (J Toxicol Sci 38:403): N-diethylnitrosamine-initiated rats given dietary orphenadrine after partial hepatectomy; more GST-P-positive foci and higher expression of Cyp2b1/2, Cyclin D1 and oxidative stress markers, with nuclear CAR localization; the authors propose CAR activation plus oxidative stress (OpenAlex abstract; the individual marker genes and the dietary dose were not in the abstract) [15]. Leurs et al. 1989 (J Pharm Pharmacol): in rat liver microsomes the known cytochrome P-450 complexation by orphenadrine was inhibited by glutathione 0.1 to 1.0 mM; the in vivo findings in that abstract (no fall in hepatic glutathione, no rise in oxidized glutathione) refer to nefopam, an orphenadrine analogue, and are not orphenadrine data (OpenAlex abstract) [16].

Mechanism

Named in rodents: CAR nuclear translocation with CYP2B induction and oxidative stress in liver [15]; antioxidant, anti-inflammatory and mitochondrial-preservation effects in ischemic brain per the authors' conclusion [17]; glutathione competes with orphenadrine-P450 complexation in vitro [16].

Counter-evidence held on record

Counter-evidence and limits Tier B only. The stroke study tests an injury state against untreated injury, not baseline redox status, at intraperitoneal doses whose human equivalence was not stated. The liver study is a tumor-promotion toxicology design; whether CAR activation or oxidative stress occurs in people at labeled doses was not addressed by any source opened. A companion paper from the same group (combined phenobarbital and orphenadrine, J Toxicol Sci 2013, PMID 23665940) was seen by title only and is not an independent line of evidence [28]. No class extrapolation was made. Framing caution Do not describe orphenadrine as an antioxidant, and do not describe it as causing oxidative stress or glutathione loss. These are animal findings in opposite directions. No antioxidant supplement is implied.

Items seen only as titles or listing gists in the PubMed listings, not opened. — Intestinal obstruction complicating orphenadrine treatment (BMJ 1976, PMID 1247718; an OpenAlex lookup was refused, 429); Inhibition of oxidative drug metabolism by orphenadrine (Mol Pharmacol 1989, PMID 2725477); Spectral interaction of orphenadrine and its metabolites with hepatic P-450 (Biochem Pharmacol 1982, PMID 7138571); Enhanced liver tumor promotion by phenobarbital and orphenadrine (J Toxicol Sci 2013, PMID 23665940); In vitro and in vivo protective effect of orphenadrine on glutamate neurotoxicity (Neuropharmacology 1999, PMID 10340304); Novel insight into antimicrobial resistance phenotypes in Staphylococcus aureus (Microbiol Res 2014, PMID 25081379; OpenAlex had no abstract); Chou 2004 muscle relaxant systematic review (PMID 15276195); Pilot study of orphenadrine for cramps in cirrhosis (PMID 29774156); Neuroferritinopathy GeneReviews (PMID 20301320).Not opened. No fact beyond the title or listing gist was used, and no grade rests on any of them.

Copper and Iron Balance

Copper and iron are assessed separately. Nothing here is counted twice.

Copper

Not graded — disclosed evidence gap

See study details

No evidence was retrieved that orphenadrine alters copper absorption, status, ceruloplasmin or copper-dependent function.

Full detail and limits

What the grade means here: Nothing has been measured here, so this finding cannot be graded. That does not establish either safety or harm, and it is not the same as a White result. Ungraded

Limits on what this shows

Why no grade: Dual condition met: no Tier B or C evidence on copper was found (the three records are not biology), and no circulating copper claim for orphenadrine was found. Not a finding of safety.

What was searched

PubMed listing orphenadrine copper: 3 records, all chemistry (a copper metal-organic framework electrochemical sensor for orphenadrine citrate, 2023; Cu(II)-catalyzed asymmetric synthesis of orphenadrine, 2012; a 1974 pharmacopoeia heavy-metal limit test) [27]. The three labels and the Norgesic label summary mention no copper or mineral interaction [1][2][3][6]. The Wikipedia orphenadrine page names no nutrient interaction [8]. The sibling dossiers in b010 to b014 contain no orphenadrine text. Repair re-check 2026-10-07: PubMed listing orphenadrine ceruloplasmin was refused (HTTP 429, not retried on that page after a wait of several minutes); no new copper source was opened. PubChem pug_view Drug Warnings section for orphenadrine (CID 4601), opened on the repair pass: contraindications (acute-angle closure glaucoma, myasthenia gravis) and cautions (GI obstruction, urinary retention, tachycardia) only, no mention of copper [29].

Channel outcomes

Gap type

Genuine gap on the PubMed channel that opened; tooling-limited for secondary channels (web search, Crossref and OpenAlex search, Europe PMC). Kept independent of Iron (Hard Rule 7).

Iron

Not graded — disclosed evidence gap

See study details

No evidence was retrieved that orphenadrine alters iron absorption, stores, ferritin or iron-deficiency anemia.

Full detail and limits

What the grade means here: Nothing has been measured here, so this finding cannot be graded. That does not establish either safety or harm, and it is not the same as a White result. Ungraded

Limits on what this shows

Why no grade: Dual condition met: no Tier B or C evidence on iron was found, and no circulating iron claim for orphenadrine was found. Not a finding of safety.

What was searched

PubMed listing orphenadrine iron: 3 records, none on iron status (a GeneReviews neuroferritinopathy chapter that lists orphenadrine among drugs with some symptomatic response and advises against iron supplements, seen as listing gist only; a 1980 BMJ paper on childhood poisoning deaths naming both orphenadrine and iron; a 1974 pharmacopoeia heavy-metal limit test) [27][28]. orphenadrine anemia returned a 404 page; orphenadrine blood returned 10 records with no iron or hematology result [27]. Labels read list no iron interaction [1][2][3]. For the orphenadrine, aspirin and caffeine combination, the label lists rare GI hemorrhage due to the aspirin content [6]; that is a combination-product note about the aspirin component and is not graded here. Repair re-check 2026-10-07: no iron-specific query could be completed on the repair pass (HTTP 429); no new iron source was opened. PubChem pug_view Drug Warnings section for orphenadrine (CID 4601), opened on the repair pass: contraindications (acute-angle closure glaucoma, myasthenia gravis) and cautions (GI obstruction, urinary retention, tachycardia) only, no mention of iron [29].

Channel outcomes

Gap type

Genuine gap on the PubMed channel that opened; tooling-limited for secondary channels. Anemia is an outcome and not iron deficiency (Hard Rule 2).

Gut Microbiome Risk

Each finding below is counted once, in this area only.

Gut microbiome risk: CLASS EXTRAPOLATION from trihexyphenidyl in a rodent model; no orphenadrine data

Yellow — Low

See study details

No study measured the gut microbiome of people or animals given orphenadrine; the only support is a Tier C rodent study of another anticholinergic, trihexyphenidyl, in which chronic dosing and withdrawal were accompanied by dysbiosis, and orphenadrine was not in that study.

Full detail and limits

Limits on what this shows

Key null findings: PubMed listings: orphenadrine microbiota and orphenadrine microbiome both returned a 404 page (the PubMed no-match response, interpreted as zero results but not independently confirmed); orphenadrine gut was refused (HTTP 429, not retried); orphenadrine intestinal returned 8 records, none on microbiota [27]. In healthy volunteers, orphenadrine 35 mg given with paracetamol did not change paracetamol pharmacokinetics in a 10-person crossover (carisoprodol and chlormezanone arms also null), an upper-GI absorption endpoint and not a colonic transit or microbiome measure [19].
At-risk subgroups: Older adults and people on other anticholinergics or opioids would plausibly carry more motility effect, but no retrieved study stratified for this. One case report titled "Intestinal obstruction complicating orphenadrine treatment" (BMJ 1976) was seen by title only and is not used for any fact [28].

Direction

Unmeasured risk flag (composition or diversity change, direction unknown). Slowed gut transit is orphenadrine's own anticholinergic effect and is not a nutrient finding (Hard Rule 2).

Regulatory status

The labels read contain no microbiome statement. They list constipation and gastric irritation among adverse reactions and contraindicate use in pyloric or duodenal obstruction and stenosing peptic ulcer [1][2][3].

Population evidence

CLASS EXTRAPOLATION, Tier C, capped at yellow. Cohort test: orphenadrine was NOT in the cohort. Baslam et al. 2023 (Antioxidants 13:26): trihexyphenidyl, an anticholinergic used in parkinsonism, studied in a dependence and withdrawal model with behavioral tests, biochemistry, gut microbiome assessment by MALDI-TOF mass spectrometry and oxidative stress measures; the authors report severe withdrawal syndrome with elevated oxidative stress and dysbiosis (OpenAlex abstract; the species and dosing details were not in the record read; the study concerns trihexyphenidyl and an Anacyclus pyrethrum extract) [21]. Wei et al. 2025 (J Oral Microbiol): NHANES 2009 to 2012, 1,596 adults aged 55 to 69 on at least one prescription; anticholinergic burden scores were inversely associated with oral microbiome alpha diversity; this is the oral and not the gut microbiome, drugs were scored by burden scale and not individually, and orphenadrine was not named in the abstract, so it fails the cohort test and carries no weight [22].

Mechanism

Three candidate routes, none tested for orphenadrine: reduced salivary secretion (labeled dry mouth), slowed GI transit (labeled constipation, anticholinergic effect), and direct effects on bacteria. The third has no orphenadrine support: the one orphenadrine-related bacterial record found was a Staphylococcus aureus efflux pump paper with no abstract available, so nothing is drawn from it [28].

Counter-evidence held on record

Counter-evidence and limits Confounding by indication is presumed (Hard Rule 6): people taking orphenadrine have acute musculoskeletal pain and often other drugs and reduced activity, and no retrieved study separates these from the drug. The trihexyphenidyl result comes from a withdrawal model, which may not reflect ordinary oral therapy, and its exposure and species were not seen. Orphenadrine and trihexyphenidyl share antimuscarinic action but differ in other pharmacology (orphenadrine also has H1, NMDA and sodium channel activity per a general reference [8]); the extrapolation is therefore a hypothesis only. Sibling dossiers for other anticholinergics (dicyclomine, hyoscyamine, glycopyrrolate, trihexyphenidyl) were read for context; orphenadrine is not in the text of any finished dossier and none of their sources are cited here beyond the two papers opened directly. Framing caution Not a statement that orphenadrine alters the gut microbiome, and not a deficiency claim. Constipation is a labeled drug effect, not a nutrient problem. No probiotic or supplement is implied.

Oxygen and ATP Output

Oxygen delivery and ATP production are assessed separately. Nothing here is counted twice.

ATP production: reverse direction, higher brain ATP concentration in rats (1963); tissue level, not synthesis

Yellow — Low

See study details

In a 1963 rat study orphenadrine increased brain adenosine triphosphate and decreased adenosine diphosphate, as did several antidepressants, while diphenhydramine tended to lower ATP; no study measured ATP synthesis or cellular energy output in people taking orphenadrine.

Full detail and limits

Limits on what this shows

Key null findings: PubMed listing orphenadrine ATP returned 3 records: [18], a cirrhosis cramp systematic review (title and gist only) and a Staphylococcus aureus efflux pump paper whose OpenAlex record had no abstract (keyword match only) [27][28]. No human ATP, phosphocreatine, respirometry or lactate measurement was found.
At-risk subgroups: None identified.

Direction

Reverse (a higher tissue ATP concentration). It is a concentration in one tissue and not a measure of mitochondrial ATP synthesis, so it supports a yellow context entry only.

Regulatory status

No energy-metabolism content in the label texts read [1][2][3].

Population evidence

None in humans. Tier B, orphenadrine in the study. Lewis and Van Petten 1963 (Br J Pharmacol Chemother): effects of iproniazid, isoniazid, phenelzine, pheniprazine, tranylcypromine, harmine, imipramine, amitriptyline, orphenadrine, diphenhydramine and cocaine on adenine nucleotides, phosphocreatine and inorganic phosphate in rat brain; every compound except harmine and diphenhydramine increased brain ATP, and every compound except imipramine and cocaine decreased ADP; the authors relate the rise in the ATP to ADP ratio to behavioral signs of CNS stimulation (OpenAlex abstract; dose, route and timing were not in the abstract) [18].

Mechanism

Not stated; the authors suggest a relationship with CNS stimulating behavior [18].

Counter-evidence held on record

Counter-evidence and limits Tier B, a single 1963 acute rat study on one tissue. Diphenhydramine, the closest structural relative named in the abstract, moved the other way (tended to decrease), so the result does not extend even within the diphenylmethane ethers; no class extrapolation is made. The Mitochondrial burden entry rests on a different paper; the ATP entry does not support it and it does not support this entry. Framing caution Do not present this as orphenadrine raising or lowering energy production in people. It is an old rodent tissue-concentration finding. No supplement is implied.

Oxygen delivery/utilization: labeled very rare aplastic anemia without established causality (drug adverse reaction, not a deficiency)

Yellow — Low

See study details

The orphenadrine labels state that very rare cases of aplastic anemia have been reported with the tablets and that no causal relationship has been established, and recommend periodic blood, urine and liver function monitoring in prolonged use; no study measured hemoglobin, hematocrit, red-cell mass or oxygen delivery in orphenadrine users.

Full detail and limits

Limits on what this shows

Key null findings: No hemoglobin, hematocrit, reticulocyte, oxygen saturation or methemoglobin measurement in orphenadrine users was found. The label itself says no causal relationship has been established.
At-risk subgroups: None identified in retrieved data. Combination product note (not graded): the aspirin, caffeine and orphenadrine label lists "Rare G.I. hemorrhage due to aspirin content" and has its own aspirin-related warnings; blood loss in that product would come from the aspirin component and not from orphenadrine [6].

Direction

Drug adverse reaction listing (idiosyncratic marrow event), causality explicitly not established. Not a depletion, retention or oxygen-delivery deficiency in the nutrient sense, and anemia is an outcome and not a nutrient (Hard Rule 2). Hemolysis and G6PD are handled in their own ungraded entry.

Regulatory status

Lupin extended-release tablet label (revision 10/2024 as reported by the fetch tool): "Very rare cases of aplastic anemia associated with the use of orphenadrine tablets have been reported," and "Safety of continuous long-term therapy with orphenadrine has not been established. Therefore, if orphenadrine is prescribed for prolonged use, periodic monitoring of blood, urine and liver function values is recommended" [1]. The Amneal label as summarized carries the aplastic anemia sentence with "No causal relationship has been established" [2]; the injection label carries the monitoring sentence [3], and the drugs.com injection page repeats the aplastic anemia sentence [5]. The label states no frequency.

Population evidence

None retrieved. PubMed listings: orphenadrine aplastic returned a 404 page (no-match response); orphenadrine anemia returned a 404 page; orphenadrine hemoglobin returned 1 record, a diabetes pain survey in which hemoglobin A1c context is unrelated to oxygen delivery; orphenadrine blood returned 10 records (overdose, forensic, bioequivalence and thyroxine assay papers, none on hemoglobin or red-cell indices) [27]. The Wikipedia methemoglobinemia page does not mention orphenadrine [26].

Mechanism

Not stated in any source read.

Counter-evidence held on record

Counter-evidence and limits The only support is a regulatory adverse-reaction sentence that disclaims causality. Frequency, mechanism and any dose relationship are not available from the sources read. The sibling muscle relaxant dossiers (metaxalone, methocarbamol) report hemolysis findings for those molecules; orphenadrine was not in their cohorts and nothing is carried over. Framing caution Do not present this as orphenadrine lowering iron, hemoglobin or oxygen delivery through a nutrient mechanism. It is a labeled very rare event with causality not established. No supplement is implied.

Claims checked and not supported

These circulate online for this medication. They are listed here only so they can be answered, never as findings, and they are not graded.

A claim with no supporting evidence is not necessarily disproven. Where evidence actually argues against a claim, that is stated below.

No circulating orphenadrine nutrient-depletion claim located
Where it comes from: Pages opened: the orphenadrine injection label page on drugs.com [5], the Norgesic combination label page [6], three DailyMed labels [1][2][3], the Wikipedia orphenadrine page [8] and DrugBank [12]; none names a vitamin, mineral or depletion. Consumer depletion handbooks, retailer pages and practitioner blogs for orphenadrine were not enumerated: web search was exhausted and no such page was opened.
Why it fails: There is nothing to rebut from the sources reached. This is not a finding that no such claim exists elsewhere. If a claim (for example magnesium, B vitamins, iron, or hemolysis in G6PD deficiency) is found later, it should be graded against the evidence recorded here, which currently supports no depletion. The labeled very rare aplastic anemia is an adverse reaction and not a nutrient claim [1][2].

How the body handles this medication

Label content: The labels read state only that "The mode of therapeutic action has not been clearly identified, but may be related to its analgesic properties," that orphenadrine "does not directly relax tense muscles in man" and "possesses anti-cholinergic actions." They contain no absorption, metabolism, elimination, half-life, protein binding or urinary excretion data and no CYP statement. Indication: adjunct for discomfort of acute painful musculoskeletal conditions. WHO defined daily dose 0.12 g, oral and parenteral.[1][2][3][7] label texts via summarizing fetch tool; revision 10/2024 (Lupin), 2019 (Amneal), May 2023 (injection) as reported by the tool
Metabolism and enzymes: Biotransformation mainly hepatic; DrugBank text lists N-demethyl and N,N-didemethyl orphenadrine as active metabolites. HSDB text lists oxidative dealkylation to secondary and primary amines and 2-methylbenzhydrol, and eight human urinary products including glucuronides (13.0% of dose), orphenadrine N-oxide (4.6%), secondary amines (8.1%) and primary amines (4.4%). No CYP isoform is named in the sources read for humans.[9] PubChem annotation text (DrugBank, HSDB) via summarizing fetch tool; percentages as rendered by the tool; [8]
Induction and inhibition: In rats orphenadrine is a cytochrome P450 2B inducer with CAR nuclear translocation [15]; an HSDB excerpt quoting a 1976 textbook says induction occurs in young rats and is absent in older ones [11]. In patients on chlorpromazine, adding orphenadrine shortened antipyrine half-life [14]. A 1989 paper title and a 1982 paper title describe P450 complexation and inhibition by orphenadrine (titles only, not opened) [28]. Human induction at labeled doses on nutrient-metabolizing enzymes was not found.[11][14][15][28]; [14] and [15] OpenAlex abstracts
Elimination, half-life and accumulation: Five healthy men given 100 mg orphenadrine hydrochloride: elimination half-life 13.2 to 20.1 hours; during repeated dosing plasma concentrations exceeded single-dose predictions by a factor of 2 to 3 and post-treatment half-lives were 2 to 3 fold longer; dog experiments suggested competition for biotransformation between orphenadrine and N-demethylorphenadrine. A general reference lists renal and biliary elimination, about 90% bioavailability and about 95% protein binding; those figures were not verified against a primary source.[13] abstract via Springer page; [8] reference only, not used for grading
Absorption and interactions: The labels read name no food, mineral, vitamin or antacid interaction; the only drug interaction named is propoxyphene (confusion, anxiety, tremor). In 10 healthy volunteers orphenadrine 35 mg did not change paracetamol pharmacokinetics, with carisoprodol and chlormezanone arms also null. Whether orphenadrine alters non-heme iron, B12 or other absorption was not studied in any source found.[1][19]
Special populations and combination product: Contraindications: glaucoma, pyloric or duodenal obstruction, stenosing peptic ulcer, prostatic hypertrophy or bladder neck obstruction, cardiospasm (megaesophagus), myasthenia gravis. Prolonged use: periodic blood, urine and liver function monitoring advised. Hepatic and renal pharmacokinetics are not in the labels read. A general PubChem record states orphenadrine has not been linked to liver injury (source section not identified). Combination tablets contain orphenadrine citrate 25 mg, aspirin 385 mg and caffeine 30 mg; label adds contraindication with aspirin or caffeine hypersensitivity, Reye syndrome and pregnancy warnings.[1][3][6][10]; combination label via drugs.com summary, revision 05/2022 as reported
Mechanism screen, classes A to I: A absorption interference: none documented. B enzyme induction: present in rodents and one human antipyrine finding, no nutrient measured. C renal wasting: none documented. D cofactor antagonism: none documented. E mitochondrial or conjugation loss: none documented in humans; rat expression data only. F dilutional or hormonal: none documented. G microbiome disruption: untested for this drug. H changed intake: labeled dry mouth, nausea, vomiting. I increased utilization: none documented.[1][2][3][13][14][15][17][20]

What the research says is worth watching

General information from the medication label and the studies above. It is not personal medical advice, and any change belongs with your prescriber.

Label / prolonged use
Blood, urine and liver function values
For prolonged use the label recommends periodic monitoring of blood, urine and liver function values, because long-term safety has not been established [1][3]. No nutrient test is specified.
Anticholinergic effects
Dry mouth, constipation, urinary retention, blurred vision
These are labeled, dose-related effects [1][3]. Contraindications include glaucoma, pyloric or duodenal obstruction, prostatic hypertrophy and myasthenia gravis. Persistent constipation or poor intake is a matter for a prescriber or pharmacist; it is a drug effect and not a nutrient finding.
Hematologic / only if prompted
Unexplained bruising, infection or marked fatigue
The label reports very rare aplastic anemia with no causal relationship established [1][2]. A blood count and a prescriber's evaluation are the response. This is a drug-safety matter, not a nutrient finding.
Combination product (note)
Orphenadrine with aspirin and caffeine
The combination label adds aspirin-related statements: rare GI hemorrhage due to the aspirin content, Reye syndrome in children with viral illness, avoidance from about 30 weeks of pregnancy, and DRESS reports [6]. These are not graded in this dossier. Ask a prescriber or pharmacist before using it with other aspirin or NSAID products.
Interaction / enzyme induction
Chlorpromazine and propoxyphene
Adding orphenadrine to chlorpromazine lowered plasma chlorpromazine concentrations and shortened antipyrine half-life in patients; the authors advise against routine co-prescription [14]. The label notes confusion, anxiety and tremor with propoxyphene [1]. No vitamin or mineral separation interval applies because no such interaction was found.
Pregnancy / pediatric / nutrient labs
Special groups and routine testing
Pregnancy and pediatric statements for the plain orphenadrine labels were not in the sections read; the combination label has pregnancy warnings [6]. No nutrient lab is indicated by orphenadrine itself on current evidence; baseline testing depends on the person's other drugs and conditions.

Overlap map, to prevent double counting

Entries resting on the same underlying source, mechanism or empty search.

Oxidative stress
Shares evidence with: Mitochondrial burden
Note: Both draw on the same Balhara 2026 rat stroke paper [17] (malondialdehyde, nitrite, glutathione and catalase for oxidative stress; HIF-1α and TFAM for mitochondria). One animal study, not two lines of evidence.
Oxidative stress
Shares evidence with: Vitamin D and other vitamins (enzyme induction route)
Note: Both cite the Morita 2013 rat paper [15] (CYP2B induction, CAR, oxidative stress genes). The ungraded entry uses it only to show the induction mechanism is present.
Mitochondrial burden
Shares evidence with: ATP production
Note: Different sources (rat stroke paper [17] versus the 1963 rat brain nucleotide paper [18]). The ATP entry does not support the mitochondrial entry and vice versa; the shared absence of any human measurement is one gap.
Gut microbiome risk
Shares evidence with: Dietary intake
Note: Both rest on the same labeled anticholinergic adverse reactions (dry mouth, constipation, nausea) [1][3]. The microbiome entry adds only the Tier C trihexyphenidyl study [21].
Oxygen delivery/utilization
Shares evidence with: Hemolysis and G6PD; Iron
Note: The label aplastic anemia sentence [1][2] is the only hematologic statement for all three. The hemolysis and iron entries rest on empty PubMed listings only, and their searches overlap (orphenadrine blood, anemia). Kept as separate entries.
Copper
Shares evidence with: Iron
Note: Searched with overlapping PubMed queries that returned no biological record. Kept as two independent entries (Hard Rule 7).
Oxygen delivery/utilization
Shares evidence with: ATP production
Note: No shared source. Kept as two independent entries (Hard Rule 7).
Hyponatremia
Shares evidence with: None
Note: Rests on empty PubMed listings and the three labels only.

All references used above

Orphenadrine citrate extended-release tablets, DailyMed label (Lupin Pharmaceuticals; set ID 7b76c8a7-dd0c-481c-8299-26dfd38ce066). — Regulatory label (Tier A). Source of the clinical pharmacology statement, contraindications, warnings, precautions (propoxyphene; prolonged-use monitoring), adverse reactions (dry mouth first; constipation; aplastic anemia) and no-PK finding.Read through a summarizing fetch tool; quotations are the tool's rendering. Revision 10/2024 as reported by the tool, not verified.
Orphenadrine citrate extended-release tablets, DailyMed label (Amneal Pharmaceuticals; set ID 6e89e43d-a3fc-481e-8aed-d6955fa2a14b). — Regulatory label (Tier A). Used for indication, contraindications, adverse reactions and the aplastic anemia causality sentence.Read through a summarizing fetch tool; last-updated December 27, 2019 as reported. The tool reported no precautions text for this label, which differs from the Lupin label; the difference was not resolved.
Orphenadrine citrate injection, DailyMed label (Hikma Pharmaceuticals USA; set ID ed406e8a-ec00-4711-ae2b-3c5af4f15438). — Regulatory label (Tier A). Source of the sodium metabisulfite excipient and sulfite warning, precautions with the prolonged-use laboratory monitoring sentence, and adverse reaction text.Read through a summarizing fetch tool; revision May 2023 and DailyMed update August 8, 2024 as reported. The Sandoz extended-release label listed in the search was not opened.
DailyMed search listing for orphenadrine (47 results). — Used only to find the label set IDs above and to see that tablet, injection and combination (aspirin and caffeine) products exist.Read through a summarizing fetch tool; set ID links as rendered by the tool. A DailyMed REST services page was refused (HTTP 429) and not retried.
Orphenadrine citrate injection, drugs.com professional label text. — Regulatory label text (Tier A). Source of the statement that adverse reactions are mainly due to the mild anticholinergic action and are usually dose related, aplastic anemia sentence and overdose statement (minimum lethal dose 2 to 3 grams in adults).Read through a summarizing fetch tool. Injection label only.
Norgesic (orphenadrine citrate, aspirin and caffeine) tablets, drugs.com professional label text. — Regulatory label text for the combination (Tier A). Used for composition, contraindications, Reye syndrome, pregnancy, DRESS, prolonged-use monitoring and "Rare G.I. hemorrhage due to aspirin content". Combination note only; nothing is graded from it.Read through a summarizing fetch tool; label revision 05/2022 as reported. The summary did not mention G6PD.
WHO Collaborating Centre, ATC/DDD Index, code M03BC01. — Reference index. Orphenadrine (citrate), group M03BC "Ethers, chemically close to antihistamines"; DDD 0.12 g, oral and parenteral.Read through a summarizing fetch tool.
Wikipedia: Orphenadrine. — Reference summary (not a primary source). Used for the second ATC code N04AB02, brand names, the reference list (including Labout 1982) and pharmacology statements; its bioavailability and protein binding figures were not verified.Read through a summarizing fetch tool. Not used to support any grade.
PubChem compound record for orphenadrine (CID 4601), Metabolism/Metabolites annotation. — Annotation text from DrugBank and HSDB (Tier B reference). Source of active metabolites, oxidative dealkylation products and the eight-urinary-product percentages.Read through a summarizing fetch tool; percentages and wording as rendered. One summarized phrase about about 50% of a residue excreted unchanged was ambiguous and is not used.
PubChem compound record for orphenadrine (CID 4601), full record. — Aggregated record. Used for mechanism of action text and a statement that orphenadrine has not been linked to liver injury (the source section of that statement was not identified).Read through a summarizing fetch tool; only the first 100,000 of 118,136 characters were read.
PubChem compound record for orphenadrine (CID 4601), Non-Human Toxicity Excerpts annotation (HSDB). — Excerpt quoting Testa B, Jenner P. Drug Metabolism: Chemical and Biochemical Aspects, 1976, p. 399, on enzyme induction in young versus older rats (Tier B, secondary quotation).Read through a summarizing fetch tool. The original textbook was not opened.
DrugBank: Orphenadrine (DB01173). — Reference page. Only mechanism and indication were visible; interaction and PK sections require sign-in.Read through a summarizing fetch tool; no PK data visible. Not used to support any grade.
Labout JJM, Thijssen CT, Keijser GGJ, Hespe W. Difference between single and multiple dose pharmacokinetics of orphenadrine hydrochloride in man. Eur J Clin Pharmacol 1982;21(4):343-350. — Pharmacokinetic study, 5 healthy men plus patients (Tier A for PK; this drug). DOI 10.1007/BF00637624; PMID 7056281.Abstract only, via the Springer page through a summarizing fetch tool; the OpenAlex record had no abstract. Full text not opened.
Loga S, Curry S, Lader M. Interactions of orphenadrine and phenobarbitone with chlorpromazine: plasma concentrations and effects in man. Br J Clin Pharmacol 1975. — Clinical interaction study in psychotic patients on chlorpromazine, 5-patient pilot and 12-patient 15-week study (Tier A; this drug in cohort). DOI 10.1111/j.1365-2125.1975.tb01576.x; PMID 791320.Abstract via a reconstructed OpenAlex record through a summarizing fetch tool; full text not opened.
Morita R, et al. Liver tumor promoting effect of orphenadrine in rats and its possible mechanism of action including CAR activation and oxidative stress. J Toxicol Sci 2013;38(3):403. — Rodent two-stage carcinogenesis study (Tier B; this drug). DOI 10.2131/jts.38.403; PMID 23665939.Abstract via a reconstructed OpenAlex record through a summarizing fetch tool; full text not opened; dietary dose not seen.
Leurs R, Donnell D, Timmerman H, Bast A. Interaction of nefopam and orphenadrine with the cytochrome P-450 and the glutathione system in rat liver. J Pharm Pharmacol 1989. — In vitro and rat study (Tier B; orphenadrine in the in vitro complexation experiment; the in vivo glutathione results in the abstract concern nefopam). DOI 10.1111/j.2042-7158.1989.tb06483.x; PMID 2570834.Abstract via a reconstructed OpenAlex record through a summarizing fetch tool; full text not opened.
Balhara P, Ahmed S, Vasudeva N, Jangir BL, Sharma S. Neuroprotective potential of orphenadrine in focal cerebral ischemia: a neurobehavioral and mechanistic study. Toxicol Appl Pharmacol 2026;510:117757. — Rat middle cerebral artery occlusion study (Tier B; this drug). DOI 10.1016/j.taap.2026.117757; PMID 41679394.Abstract as summarized from a PubMed search-listing record through a summarizing fetch tool (not verbatim); the OpenAlex record had no abstract; the Elsevier linking page returned no content and ScienceDirect was disallowed; full text not opened.
Lewis JJ, Van Petten GR. The effect of antidepressive drugs and some related compounds on the levels of adenine nucleotides, inorganic phosphate and phosphocreatine in the rat brain. Br J Pharmacol Chemother 1963. — Rat brain nucleotide study (Tier B; orphenadrine and diphenhydramine among compounds tested). DOI 10.1111/j.1476-5381.1963.tb01483.x; PMID 19108178.Abstract via a reconstructed OpenAlex record through a summarizing fetch tool; full text not opened; dose and route not seen.
Saano V, Elo HA, Paronen P. Effect of central muscle relaxants on single-dose pharmacokinetics of peroral paracetamol in man. Int J Clin Pharmacol Ther Toxicol 1990. — Randomized double-blind crossover, 10 healthy volunteers, orphenadrine 35 mg among the arms (Tier A for the endpoint; this drug in cohort). PMID 2303311.Abstract via a reconstructed OpenAlex record through a summarizing fetch tool; full text not opened. The endpoint is paracetamol exposure, not a nutrient.
Abd-Elsalam SM, et al. Orphenadrine in treatment of muscle cramps in cirrhotic patients: a randomized study. Eur J Gastroenterol Hepatol 2019 (OpenAlex; PubMed listing shows 2020). — Randomized placebo-controlled trial, 124 patients (Tier A for adverse events; this drug). DOI 10.1097/meg.0000000000001622; PMID 31834056.Abstract via a reconstructed OpenAlex record through a summarizing fetch tool; no dose, frequencies or laboratory values in the abstract; full text not opened.
Baslam A, et al. Trihexyphenidyl alters its host's metabolism, neurobehavioral patterns, and gut microbiome feedback loop: the modulating role of Anacyclus pyrethrum. Antioxidants 2023;13(1):26. — Rodent dependence and withdrawal model (Tier C for orphenadrine; trihexyphenidyl studied). DOI 10.3390/antiox13010026; PMID 38275646.CLASS EXTRAPOLATION source: orphenadrine was not in this study. Abstract via a reconstructed OpenAlex record through a summarizing fetch tool; species and dosing not seen; full text not opened.
Wei K, et al. Polypharmacy, anticholinergic burden and oral microbiome among U.S. middle-aged and older adults: a representative national survey. J Oral Microbiol 2025. — Cross-sectional NHANES 2009 to 2012, 1,596 adults aged 55 to 69 (Tier C). DOI 10.1080/20002297.2025.2580559; PMID 41211602.Fails the cohort test: orphenadrine not named, drugs scored by burden scales, oral not gut microbiome. Carries no weight. Abstract via OpenAlex through a summarizing fetch tool.
Brown JH, Mackey HK. Further studies on the erythrocyte anti-inflammatory assay. Proc Soc Exp Biol Med 1968. DOI 10.3181/00379727-128-33051; PMID 5663264. — In vitro erythrocyte heat-hemolysis assay paper returned by the PubMed query for orphenadrine AND hemolysis.The abstract opened does not mention orphenadrine and reports no orphenadrine result. Not used to support any claim.
Wikipedia: Glucose-6-phosphate dehydrogenase deficiency. — Reference page. Does not mention orphenadrine; lists primaquine, tafenoquine, dapsone, methylene blue, pegloticase, rasburicase and toluidine among agents to avoid.Read through a summarizing fetch tool. Reference only; absence from this page is not evidence of safety.
Wikipedia: Hyponatremia. — Reference page. Does not mention orphenadrine, muscle relaxants or anticholinergics.Read through a summarizing fetch tool. Reference only.
Wikipedia: Methemoglobinemia. — Reference page. Does not mention orphenadrine.Read through a summarizing fetch tool. Reference only.
PubMed search listings (format=pubmed), accessed 2026-10-07. Queries run and outcome: orphenadrine AND (hemolysis OR G6PD), 1 record; orphenadrine glucose-6-phosphate dehydrogenase, 404; orphenadrine hyponatremia, 404; orphenadrine sodium, 10 of 33 records; orphenadrine mitochondrial, 2; orphenadrine oxidative, 10; orphenadrine ATP, 3; orphenadrine iron, 3; orphenadrine copper, 3; orphenadrine anemia, 404; orphenadrine aplastic, 404; orphenadrine hemoglobin, 1; orphenadrine blood, 10; orphenadrine vitamin, 9; orphenadrine dry mouth, 4; orphenadrine intestinal, 8; orphenadrine microbiota, 404; orphenadrine microbiome, 404; anticholinergic gut microbiome, 10; orphenadrine focal cerebral ischemia, 1. Repair pass (2026-10-07): orphenadrine ascorbic acid, 2 records (PMIDs 5396467, 5409400, analytical); orphenadrine vitamin D, 1 record (PMID 35677500, cirrhosis cramp systematic review, gist only); orphenadrine SIADH, 404. — Search listings (index of records, not studies). Refused or not run: orphenadrine gut (429), orphenadrine saliva and xerostomia (429), orphenadrine G6PD alone and orphenadrine AND hyponatremia OR SIADH (429), a combined mitochondria OR oxidative OR ATP boolean query (returned the PubMed trending page, discarded). Repair pass refused (429): orphenadrine hyponatraemia, orphenadrine hemolytic (4 attempts), orphenadrine ceruloplasmin.Read through a summarizing fetch tool. A 404 page is read as the PubMed no-match response and was not independently confirmed. The base URL is shown; each listing used the query text above.
Items seen only as titles or listing gists in the PubMed listings, not opened. — Intestinal obstruction complicating orphenadrine treatment (BMJ 1976, PMID 1247718; an OpenAlex lookup was refused, 429); Inhibition of oxidative drug metabolism by orphenadrine (Mol Pharmacol 1989, PMID 2725477); Spectral interaction of orphenadrine and its metabolites with hepatic P-450 (Biochem Pharmacol 1982, PMID 7138571); Enhanced liver tumor promotion by phenobarbital and orphenadrine (J Toxicol Sci 2013, PMID 23665940); In vitro and in vivo protective effect of orphenadrine on glutamate neurotoxicity (Neuropharmacology 1999, PMID 10340304); Novel insight into antimicrobial resistance phenotypes in Staphylococcus aureus (Microbiol Res 2014, PMID 25081379; OpenAlex had no abstract); Chou 2004 muscle relaxant systematic review (PMID 15276195); Pilot study of orphenadrine for cramps in cirrhosis (PMID 29774156); Neuroferritinopathy GeneReviews (PMID 20301320).Not opened. No fact beyond the title or listing gist was used, and no grade rests on any of them.
PubChem compound record for orphenadrine (CID 4601), Drug Warnings annotation. — Annotation text (Tier B reference), opened on the repair pass. Lists contraindications and cautions; no hematologic, electrolyte, vitamin or mineral statement.Read through a summarizing fetch tool. Used only to document an absence; supports no grade. A parallel Adverse Effects section request was refused (HTTP 429).

Orphenadrine

Findings for this medication

What the research found

Dietary intake: labeled dry mouth, nausea, vomiting and constipation; intake not measured (context flag)

Hemolysis and G6PD deficiency

Hyponatremia (sodium)

Vitamin D and other vitamins (hepatic enzyme induction route)

The five body-system areas

⚡Mitochondrial Burden

Mitochondrial burden: reverse direction, HIF-1α and TFAM expression in rat ischemic brain only

💥Oxidative Stress

Oxidative stress: opposing rodent signals, lower malondialdehyde after experimental stroke versus oxidative-stress gene expression in a rat liver tumor-promotion model

⚖️Copper and Iron Balance

Copper

Iron

🌿Gut Microbiome Risk

Gut microbiome risk: CLASS EXTRAPOLATION from trihexyphenidyl in a rodent model; no orphenadrine data

💨Oxygen and ATP Output

ATP production: reverse direction, higher brain ATP concentration in rats (1963); tissue level, not synthesis

Oxygen delivery/utilization: labeled very rare aplastic anemia without established causality (drug adverse reaction, not a deficiency)

Claims checked and not supported

No circulating orphenadrine nutrient-depletion claim located

How the body handles this medication

What the research says is worth watching

Overlap map, to prevent double counting

Mitochondrial Burden

Oxidative Stress

Copper and Iron Balance

Gut Microbiome Risk

Oxygen and ATP Output