Metoclopramide

Limits on what this shows

• Null findings: Three PubMed listings found no study of metoclopramide in hepatocyte, neuronal or other cell models with mitochondrial membrane potential, respiration, ATP or ROS outcomes: "metoclopramide mitochondria" (9 records; besides [12], [19] to [22] and two 1987 and 1990 isolated-perfused-rat-lung drug-binding papers that were not opened, the rest used metoclopramide only as a control or comparison compound), "metoclopramide with hepatocytes, neurons, cell viability, neurotoxicity or apoptosis" (27 records, all clinical reviews, case reports or pharmacovigilance), and the earlier cytotoxicity and reactive oxygen species listing (20 records). A listing for respiratory chain, complex I and membrane potential terms returned the PubMed homepage rather than results and a dedicated "metoclopramide ATP" listing returned 429; neither was retried. Robba 2009 [22] (rat adrenal zona glomerulosa, metoclopramide versus bromocriptine) carries mitochondrial ultrastructure as an indexing term, but the abstract retrieved gave no mitochondrial finding, so it is not used. Abolfazli 2024 [12] used metoclopramide 2 mg/kg only as a positive-control comparator; its full text was not opened and no metoclopramide-alone contrast is used.
• At-risk subgroups: None identifiable from these data.

Regulatory status

No mitochondrial content in the label text retrieved [1].

Population evidence

None in humans. Tier B animal studies with metoclopramide as the exposure, abstracts opened through PubMed listing pages: Laszczynska 1989 [19], rats given metoclopramide 2.2 mg/kg intraperitoneally for 14 days (prolactin about twice control); electron microscopy of epididymal caput principal cells showed reduced rough endoplasmic reticulum, Golgi distension, more apical vesicles and "changes in mitochondria", described by the authors as affecting organelles in "energetic processes"; the changes were reversible after stopping the drug. No mitochondrial count, size, cristae score or direction was given in the abstract. Amiri 1993 [20], male rats treated for 21 days: metoclopramide increased adrenal mitochondrial benzodiazepine receptor density by 31% (P < 0.05), sulpiride decreased it by 49%, and none of the three agents tested changed kidney or testis receptors; the authors concluded the organ-specific changes appear prolactin independent. Receptor density is a mitochondrial outer-membrane protein measure, not evidence of damage, dysfunction or reduced energy output. Dose was not given in the abstract.

Mechanism

Not established. In [19] the authors framed the epididymal change as a consequence of metoclopramide-induced hyperprolactinemia, so it is an indirect, endocrine-mediated effect in a non-target tissue. A direct action on mitochondria by metoclopramide was not shown in any source opened. Aldosterone-pathway mitochondrial enzyme data (18-hydroxylase activity in adrenal mitochondria, Aguilera 1984 [21]) concern steroidogenesis and are not used as a burden finding.

Counter-evidence held on record

Counter-evidence and confounding Evidence is two old rat abstracts, one without a quantified mitochondrial result and one measuring a receptor protein. Hyperprolactinemia, not a mitochondrial action of the drug, is the authors' own explanation for [19]; [20] reports a prolactin-independent receptor change in adrenal only. The doses were pharmacologic in rats and cannot be mapped to human exposure. No class extrapolation is used: dopamine antagonist or antipsychotic mitochondrial data were not opened. Framing caution Hard Rule 2: not a nutrient deficiency, and no mitochondrial injury in people is claimed. Do not recommend CoQ10, B vitamins, antioxidants or other "mitochondrial support" supplements from this entry. It is a mechanistic prompt for future research only.

Limits on what this shows

• Null findings: None located in humans. A PubMed listing for metoclopramide with oxidative stress, glutathione, lipid peroxidation or antioxidant displayed 20 of 62 records; most were unrelated, and only [11] and a 1995 radiosensitizer review (not opened) addressed the drug.

Regulatory status

No oxidative-stress warning as such. The methemoglobinemia and sulfhemoglobinemia reactions are oxidative injuries to hemoglobin [1].

Population evidence

None in humans. Van Veldhuizen 1995 [6]: case report whose authors call metoclopramide "a drug with oxidant activity" (a statement, not a measurement). Ahmad Khan 2004 [11]: rat study, title states metoclopramide attenuates iminodipropionitrile-induced oxidative stress and neurobehavioral toxicity; the abstract could not be retrieved (OpenAlex and Crossref carried none), and the statement that the protection was dose-dependent comes from a summarized PubMed listing, so detail is limited to the title and that summary. Abolfazli 2024 [12]: chicken emesis model in which metoclopramide was the standard-therapy comparator and mitochondrial lipid peroxidation, protein carbonyl, glutathione and ROS were measured; the metoclopramide-alone contrast is not in the abstract retrieved, so it is not used.

Mechanism

Hemoglobin oxidation is shown clinically [3][4][5][6]. Any antioxidant action in neural tissue is a single animal observation with the mechanism not retrieved.

Counter-evidence held on record

Counter-evidence The two directions are not reconcilable from the sources opened: hemoglobin oxidation occurs in people, while the protective effect is in rat neural tissue against a neurotoxin. The oxidant statement in [6] is an author comment, and [11] was read at title level. Framing caution Not an antioxidant-depletion claim and not an antioxidant benefit claim. Do not recommend antioxidant supplements from this entry; the hemoglobin effect is handled in the oxygen delivery entry and not double-counted.

Limits on what this shows

• Null findings: No pre- and post-initiation comparison exists in the sources opened (Hard Rule 6: confounding by indication is presumed until excluded).
• At-risk subgroups: People with gastroparesis of any cause, per [13]; not a metoclopramide subgroup.

Regulatory status

Iron is not mentioned in the label text retrieved [1].

Population evidence

Amjad 2021 [13]: cohort of 320 patients with scintigraphy-diagnosed gastroparesis, diabetic and non-diabetic; 50.8% had iron deficiency (also 48.8% vitamin D and 18.2% B12). Metoclopramide use is not reported in the abstract retrieved, so the drug is not documented in the cohort and no drug effect can be inferred.

Mechanism

Absent for metoclopramide in the sources retrieved. The drug does not suppress gastric acid. A PubMed listing for metoclopramide with iron absorption, ferritin, copper, ceruloplasmin or zinc returned no iron study with the drug.

Counter-evidence held on record

Counter-evidence and confounding Gastroparesis, reduced intake and underlying disease explain the prevalence. Iron deficiency is not anemia, and anemia is not iron deficiency (Hard Rule 2). Framing caution This is a context flag about the indication, not a finding about metoclopramide. No iron supplement is recommended; excess iron carries its own risks.

Limits on what this shows

• Why no grade: Dual condition met: no Tier B or C evidence for a copper effect and no circulating copper claim located. This is a disclosed gap, not a finding of safety. Kept independent of Iron (Hard Rule 7).

What was searched

PubMed listing "metoclopramide (iron absorption OR ferritin OR copper OR ceruloplasmin OR zinc)" (32 records, 20 displayed). Copper hits were a prolactin study in copper intrauterine device users in which metoclopramide was a pharmacologic prolactin stimulus (title only, not opened) and a chicken emesis model that used copper sulfate as the emetic challenge [12]; neither measured copper status. The listing also returned a rat study of zinc content in epididymal spermatozoa, in which metoclopramide inhibited the normal fall in sperm zinc, linked by the authors to lower testosterone [15]; this is a tissue zinc finding and is not a copper or systemic status result. The label has no copper content [1].

Channel outcomes

PubMed listing and OpenAlex lookups worked; no Crossref or Europe PMC copper search was possible beyond those. Web search unavailable. Repair pass: a dedicated "metoclopramide copper" PubMed listing and an OpenAlex keyword search both returned 429 and were not retried, so no new copper query could be completed; the earlier listing stands. Assessment: likely a genuine gap, with the circulating-claim audit tooling-limited.

Limits on what this shows

• Why no grade: Dual condition met on what was opened: no Tier B or C result attributing a microbiome change to metoclopramide, and no circulating microbiome claim located. This is not a finding of safety. Re-check the full texts of [17][18] and drug-microbiome screening datasets when access allows. No PPI or H2 blocker microbiome data are borrowed.

What was searched

PubMed listings "metoclopramide (microbiome OR microbiota OR dysbiosis OR small intestinal bacterial overgrowth)" (8 records) and "metoclopramide microbiota" (6 records). The only records with microbiota outcomes were two 2025 mouse papers in which metoclopramide induced hyperprolactinemia as a disease model and the microbiota changes reported (Desulfovibrionaceae, Staphylococcaceae, Bacteroidaceae lowered; Lactobacillus and Bifidobacterium enriched) were attributed to the test probiotic or herbal extract [17][18]. The other records mention metoclopramide only as a treatment. A third phrasing returned a 404 and was not repeated. Repair pass: a broader listing (metoclopramide with gut microbiota, microbiome, bacterial overgrowth or intestinal flora; 15 records) found 13 reviews or clinical papers in scleroderma, chronic intestinal pseudo-obstruction, Fabry disease and gastroparesis in which metoclopramide appears only as a prokinetic treatment and small intestinal bacterial overgrowth is discussed separately (antibiotics, other predisposing drugs); none reported microbiota or SIBO as an outcome of metoclopramide exposure, and none was opened beyond the listing summary. The remaining two records were the same two mouse papers [17][18].

Channel outcomes

Abstracts reached through OpenAlex (reconstructed text, via a summarizing tool); full texts of [17][18] were not opened (repair pass: the DOI links redirected to the Journal of Microbiology and Biotechnology site and to Springer, and both returned 429 and were not retried), so a metoclopramide-only versus normal-control microbiota comparison may exist in them and could support a Tier B yellow. Large drug-by-microbiome screens were not reached. Assessment: tooling-limited, probable thin literature.

Limits on what this shows

• Null findings: The adult case [4] and the infant case [3] had normal reductase activity, so the label's enzyme-deficiency subgroup does not explain all cases. A separate PubMed listing for metoclopramide with hemoglobin, anemia or hemolysis returned no records that studied metoclopramide exposure with those outcomes; the hemoglobin loss here is functional (dyshemoglobin), not red-cell mass.
• At-risk subgroups: Neonates and infants, especially at doses above the recommended range [3]; neonates exposed in utero around delivery [1]; NADH-cytochrome b5 reductase deficiency [1]; G6PD deficiency, in whom the usual antidote carries its own hemolysis risk [1][5]; renal impairment (exposure rises 2-fold or more) [1].

Regulatory status

Labeled. Section 6 hematologic disorders list "agranulocytosis, neutropenia, leukopenia, methemoglobinemia, sulfhemoglobinemia". Section 8.8: "Metoclopramide-treated patients with NADH-cytochrome b5 reductase deficiency are at an increased risk of developing methemoglobinemia and/or sulfhemoglobinemia." For G6PD deficiency with metoclopramide-induced methemoglobinemia, methylene blue treatment is not recommended; section 10 notes methylene blue may cause fatal hemolytic anemia in G6PD deficiency. Section 8.4 not recommended in pediatric patients, citing methemoglobinemia in neonates; section 8.1 lists neonatal methemoglobinemia after in utero exposure during delivery [1] (label read through a summarizing fetch tool).

Population evidence

No cohort or incidence study was found. Tier B case reports, each opened as an abstract through OpenAlex: a 3-week-old infant given 1.0 mg/kg every 6 hours for 36 hours developed cyanosis with methemoglobin 20.5% and oxyhemoglobin saturation 79%, normal methemoglobin reductase activity, resolved with one dose of IV methylene blue [3]. An adult developed methemoglobin 40.6% with oxygen saturation 59% after surgery; normal NADH-cytochrome b5 reductase activity; resolved within 24 hours of methylene blue [4]. A patient with kidney impairment and both G6PD and NADH-cytochrome b5 reductase deficiency developed cyanosis; methylene blue did not help and a hemolytic crisis followed [5]. A patient on chronic therapy developed sulfhemoglobinemia that resolved after stopping the drug [6]. A PubMed listing for "metoclopramide methemoglobinemia" displayed 16 records, about a dozen of them further metoclopramide case reports or letters in infants and adults (titles and summarized abstracts only, not opened) [7].

Mechanism

Oxidative conversion of hemoglobin iron, described by the authors of [6] as a drug "with oxidant activity". Methemoglobin is normally reduced back by NADH-cytochrome b5 reductase, so deficiency of that enzyme raises risk [1]. The adult case [4] had normal enzyme activity, so enzyme deficiency is not required. The exact molecular route for metoclopramide was not established in the sources opened.

Riboflavin note

NADH-cytochrome b5 reductase is a flavoprotein, and a PubMed listing for riboflavin with methemoglobinemia returned congenital-deficiency literature (records not opened). No record in that listing mentioned metoclopramide, and no source linking metoclopramide to riboflavin status was found. No riboflavin entry is made, and this is not evidence of a riboflavin effect (see Overlap map for the promethazine sibling).

Counter-evidence held on record

Counter-evidence and confounding Case reports cannot give incidence, and methemoglobinemia in hospitalized patients has competing causes (other oxidant drugs, topical anesthetics, acetaminophen overdose); several listed reports involve co-administered agents [7]. Orange here rests on Tier A (the label) and Tier B (case reports) only; there is no controlled study, so the grade is for existence of a bounded real effect, not for frequency. Framing caution Hard Rule 2: this is a drug adverse reaction, not a nutrient deficiency. It does not imply any vitamin or mineral shortfall and no supplement is recommended or implied. Treatment of methemoglobinemia is a clinical matter.

Limits on what this shows

• Why no grade: Dual condition met: no Tier B or C source measuring ATP or cellular energy output for metoclopramide and no circulating "low energy" claim located. This is a disclosed gap, not a finding of safety. Kept independent of Mitochondrial burden (now yellow) and Oxygen delivery/utilization (Hard Rule 7).

What was searched

The same PubMed listing as the Mitochondrial burden entry (it included the term ATP), the cytotoxicity and ROS listing, and the cell-model listing (hepatocytes, neurons, viability, apoptosis; 27 records, none a cellular study). No record measured ATP in metoclopramide-exposed cells or tissue. The only energy-related wording found is the authors' phrase "energetic processes" for organelles altered in rat epididymal cells [19], which is a description of organelle function, not an ATP measurement, and rests on one indirect rat study already used in the Mitochondrial burden entry. The functional oxygen-carrying loss from methemoglobin is an oxygen delivery matter and is not treated as an ATP result.

Channel outcomes

Listings and OpenAlex worked on the first pass; on the repair pass a PubMed listing for respiratory chain, complex I, membrane potential and ATP terms returned the homepage, a dedicated "metoclopramide ATP" listing returned 429 and was not retried, and web search stayed unavailable. [12] full text was not opened (OUP page gave the abstract only; the PubMed Central page returned a browser verification challenge). Assessment: genuine thin literature with a tooling-limited component.