Emtricitabine/Tenofovir

Limits on what this shows

• At-risk subgroups: Of 60 tubulopathy cases, 90% were on a protease inhibitor-containing regimen and 30% on didanosine [5]; older age (OR 1.1 per year) [8]; higher mid-dose TDF concentration (0.143 vs 0.108 mg/L, p = 0.04) [6]; CrCl below 60 mL/min, nephrotoxic co-medication and high-dose or multiple NSAIDs (label) [1][2].

Regulatory status

Truvada label sec 5.3: Fanconi syndrome ("renal tubular injury with severe hypophosphatemia") reported with TDF; assess serum phosphorus in chronic kidney disease; persistent or worsening bone pain, pain in extremities or fractures may indicate proximal renal tubulopathy. Sec 5.5: osteomalacia from proximal renal tubulopathy; consider hypophosphatemia in at-risk patients with persistent bone or muscle symptoms [1][2]. The Descovy (TAF) label lists proximal renal tubulopathy and Fanconi syndrome as postmarketing events with TAF-containing products [3].

Population evidence

Hamzah 2017, UK CHIC cohort [5]: 15,983 patients on at least 4 weeks of TDF-containing ART; 69 (0.4%) developed treatment-limiting tubulopathy; 60 analysed (48 proximal renal tubulopathy, 12 acute tubular injury). Hypophosphatemia (below 1.98 mg/dL) in 41 of 55 measured (75%). Ezinga 2014, Nijmegen [6]: 161 patients on TDF for at least 1 year, cross-sectional; kidney tubular dysfunction in 17 (10.6%); phosphate fractional excretion above 20% with hypophosphatemia in 15 (9.3%), 12 of 17 (70.6%) with tubular dysfunction vs 3 of 144 (2.1%) without. Havens 2013, ATN 063 [7]: 118 youth on TDF vs 85 not; tubular reabsorption of phosphate 92.0% vs 93.3% (adjusted p = 0.011); serum phosphate 3.7 vs 3.6 mEq/L as printed (adjusted p = 0.71). Labarga 2009, Madrid [8]: 284 patients (154 TDF-containing ART, 49 other ART, 81 naive); significant tubular damage (at least 2 markers, one a Fanconi criterion including hyperphosphaturia) in 22%, 6% and 12%; TDF use independently predicted it (OR 21.6, 95% CI 4.1 to 113). Separate phosphate values were not in the abstract. Obiebi 2018, Port Harcourt [9]: prospective, 57 on TDF vs 47 not; urinary phosphate (units as printed, mg/dL) 13.6 vs 10.8 at week 16 (p = 0.009) and 18.9 vs 16.3 at week 24 (p = 0.007), baseline 10.6 vs 9.8 (p = 0.465).

Mechanism

Present (class C, renal wasting). Tenofovir is cleared by glomerular filtration plus active tubular secretion, so it concentrates in proximal tubular cells; the label names the result as renal tubular injury [1][2]. In Havens, higher plasma tenofovir tracked with higher vitamin D binding protein and higher serum calcium while higher intracellular tenofovir diphosphate tracked with lower FGF23, which the authors read as separate mechanisms for the parathyroid and phosphate effects [7]. The named uptake and efflux transporters were not in the retrieved label text and the transporter literature was not opened.

Cohort test

Tenofovir disoproxil was in every cohort above. The label-quoted PrEP trials gave the fixed combination. Hamzah, Ezinga, Havens and Obiebi describe TDF-containing regimens without stating how many also received emtricitabine, so the effect is attributed to the tenofovir component; emtricitabine is not implicated by any retrieved label text.

Red/orange hunt

Held at orange, not red: the direction is consistent across five human studies with direct tubular phosphate measures and a named mechanism, but the clinically meaningful deficit is confined to a rare subgroup (0.4% treatment-limiting in [5], about 9% with biochemical phosphate wasting in a TDF-only cross-sectional sample [6]) and three Tier A sources show no excess low serum phosphate in the wider treated population (see counter-evidence).

Counter-evidence held on record

Counter-evidence on record Cooper 2010, meta-analysis of 17 studies (9 randomized) comparing TDF with non-TDF regimens: creatinine clearance 3.92 mL/min lower (95% CI 2.13 to 5.70), acute renal failure risk difference 0.7% (0.2 to 1.2), and no evidence linking TDF to severe proteinuria, hypophosphatemia or fractures [10]. Label PrEP trials, grade 2 to 4 phosphorus below 2.0 mg/dL: 10% vs 8% placebo (iPrEx, n = 1251 vs 1248) and 9% vs 9% (Partners PrEP, n = 1579 vs 1584) [1]. Havens: serum phosphate did not differ between TDF and no-TDF groups [7]. Hamzah and Ezinga have no non-TDF comparator for the proportions given. Framing caution for the consumer surface This is a renal-loss syndrome of the drug in a minority of users, a prescriber and monitoring matter. It is not a signal that people taking emtricitabine/tenofovir should increase phosphate intake or take a supplement. Most users have no clinically relevant phosphate change.

Limits on what this shows

• At-risk subgroups: As for phosphate: boosted protease inhibitor regimens, didanosine, reduced kidney function, older age [5][8].

Regulatory status

Truvada label sec 6.2 (postmarketing) lists "hypokalemia" under Metabolism and Nutrition Disorders with no frequency, and states that the listed reactions, including hypokalemia, "may occur as a consequence of proximal renal tubulopathy" (re-read in the repair pass through the summarizing fetch tool) [1]. Study 934 and the PrEP laboratory tables in the label contain no potassium row [1]. Section 5.3 names Fanconi syndrome and hypophosphatemia [1][2].

Population evidence

Hamzah 2017 [5]: among 60 patients with treatment-limiting TDF tubulopathy, hypokalemia (potassium below 3.0 mEq/L) in 3 of 44 with a measurement (7%). The cohort was 15,983 TDF-treated patients, so this is a handful of cases in a very large exposed group. Park 2026 case report with literature review [15] (Tier B): in 95 published cases of tenofovir-associated Fanconi syndrome, hypokalemia was reported in 45%; publication bias toward severe cases is likely. The index case had a potassium nadir of 3.0 mmol/L. Mathew 2006 case report [14] (Tier B): a 38-year-old man on tenofovir, lamivudine and efavirenz with potassium 1.9 mEq/L, serum phosphorus 1.2 mg/dL and bicarbonate 19 mEq/L; urinalysis normal one year after discharge. Tenofovir-induced distal renal tubular acidosis case report, J R Coll Physicians Edinb 2022 [29] (Tier B, PubMed listing snippet only): recurrent hypokalaemic paralysis attributed to tenofovir; the abstract suggests monitoring urinalysis and serum potassium and reports improvement after potassium correction. Full text not opened. Pooled hepatitis B cross-sectional study, Gastroenterol Res Pract 2016 [28]: 92 patients on adefovir or tenofovir (alone or added to lamivudine) for more than 1 year; fractional excretion of potassium was calculated and "potassium losses with hypokalemia" was one of the criteria for tubular dysfunction; proximal tubular dysfunction in 24 of 92 (26.1%). Abstract only (OpenAlex reconstruction); no per-drug or per-criterion potassium counts are in the abstract, adefovir is a different nucleotide analogue, and emtricitabine is not part of the regimen, so it cannot serve as a second potassium cohort for this drug.

Mechanism

Present (class C). Proximal tubular injury with impaired reabsorption of electrolytes and bicarbonate, with downstream potassium loss; the same tubular injury as the phosphate entry [1][2][5].

Cohort test

TDF-containing ART in [5]; emtricitabine co-administration not stated. Case reports [14][15][29] involve tenofovir with lamivudine/efavirenz or TDF alone (emtricitabine not mentioned in [15] or in the snippet of [29]). [28] pools adefovir and tenofovir users and is not counted.

Red/orange hunt

Held at orange, not red. The label now supports the direction: postmarketing hypokalemia is named as a consequence of proximal renal tubulopathy [1], but with no frequency, so it is a Tier A statement of occurrence, not a measured effect size. Only one Tier A cohort reported measured potassium (3 of 44 low, no comparator) [5]. Second-cohort search in the repair pass: Ezinga 2014 full text read through a summarizing fetch tool, no potassium mention [6]; Obiebi 2018 and Cooper 2010 report no potassium [9][10]; the pooled hepatitis B cross-sectional study [28] used potassium loss as a criterion but its abstract gives no per-drug counts and its full text could not be opened (Hindawi, DOI and Wiley routes returned client errors); PubMed and Crossref listing queries for hypokalemia in tenofovir cohorts were 429-throttled after one useful PubMed listing. Would rise to red only with a second cohort reporting measured potassium in TDF users against a non-TDF comparator.

Counter-evidence held on record

Counter-evidence on record No Tier A source found a potassium difference between TDF-treated and untreated groups in an unselected population. Obiebi 2018 did not report potassium [9]; Ezinga 2014 did not report potassium [6]; Cooper 2010 reported no hypophosphatemia or severe tubular outcome overall [10]. The label lists hypokalemia only as a rare postmarketing event with no frequency [1]. Framing caution for the consumer surface Low potassium here is a symptom of a drug-induced kidney syndrome, not a dietary shortfall. A potassium supplement on its own would not treat the cause and can be hazardous if kidney function is reduced; this is a prescriber decision.

Regulatory status

Not named in the retrieved Truvada label text; Fanconi syndrome (renal tubular injury) is named [1][2].

Population evidence

Hamzah 2017 [5]: metabolic acidosis (bicarbonate below 19 mEq/L) in 7 of 22 with a measurement (32%) among 60 tubulopathy cases from 15,983 TDF-treated patients. Park 2026 [15] (Tier B): non-anion-gap metabolic acidosis in 56% of 95 reported cases. Mathew 2006 [14] (Tier B): bicarbonate 19 mEq/L at presentation, 25 mEq/L two weeks later.

Mechanism

Present (class C): proximal tubular bicarbonate reabsorption failure. Obiebi 2018 did not measure urinary bicarbonate [9].

Cohort test

TDF in the cohort [5]; emtricitabine co-administration not stated.

Why yellow

Hard Rule 2: acidosis is a clinical outcome and bicarbonate is a buffer produced by the body, not an intake-dependent nutrient. Only one Tier A cohort measured it, in 22 cases.

Counter-evidence held on record

Framing caution for the consumer surface Not a deficiency of anything the diet supplies. It is a monitoring signal for kidney tubular injury.

Regulatory status

Not named in the retrieved label text [1][2].

Population evidence

Ezinga 2014 [6]: urate fractional excretion above 10% with low plasma urate in 7 of 161 TDF-treated patients (4.3%), 5 of 17 (29.4%) with tubular dysfunction vs 2 of 144 (1.4%) without. Labarga 2009 [8] counted hyperuricosuria among its tubular markers.

Mechanism

Present (class C): proximal tubular urate handling lost in tubular injury.

Cohort test

TDF-containing ART in both cohorts; emtricitabine not separated.

Why yellow

Urate is a metabolite, not a nutrient, low serum urate is not a deficiency state, and one Tier A source has direct plasma and fractional-excretion data.

Counter-evidence held on record

Counter-evidence on record Obiebi 2018: urine uric acid at 24 weeks 289 vs 251 in TDF vs non-TDF, p = 0.260 (not significant) [9]. Framing caution for the consumer surface A marker for the clinician, not a deficiency claim.

Regulatory status

Truvada label sec 5.5: serum parathyroid hormone and 1,25-vitamin D levels were higher in subjects receiving TDF; the effect of calcium and vitamin D supplementation "was not studied" but "may be beneficial" [1][2].

Population evidence

Havens 2013, ATN 063 [7]: 118 youth on TDF vs 85 not; PTH 47.7 vs 31.2 pg/mL (adjusted p less than 0.001); 1,25-dihydroxyvitamin D 113.7 vs 108.5 pmol/L (adjusted p = 0.016); 25-hydroxyvitamin D 20.8 vs 21.7 ng/mL (p = 0.39); serum calcium 9.4 vs 9.5 mg/dL (adjusted p = 0.19). Within the TDF group, the highest quintile of plasma tenofovir had higher vitamin D binding protein and lower free 1,25-dihydroxyvitamin D; the authors propose a "functional vitamin D deficiency" as the cause of the PTH rise. Overton 2015, ACTG A5280, Ann Intern Med [24] (second Tier A source; abstract read from an OpenAlex record): 165 treatment-naive adults randomized (79 vitamin D3 plus calcium, 86 placebo) while starting efavirenz/emtricitabine/tenofovir disoproxil fumarate; in the placebo arm median 25-hydroxyvitamin D changed by +1.7 nmol/L (IQR -13.2 to 10.7) over 48 weeks, i.e. no fall, while the supplemented arm rose by 61.2 nmol/L. PTH was not in the abstract and the full text could not be opened (ACP journal page returned a client error; PubMed record served a bot challenge).

Mechanism

Present, partly. Phosphate wasting raises 1,25-dihydroxyvitamin D and PTH; the free-calcitriol hypothesis is the authors' proposal from a quintile comparison, not a tested mechanism. A rise in 1,25-dihydroxyvitamin D runs opposite to a vitamin D deficiency state.

Cohort test

TDF-containing regimens (emtricitabine share not reported; efavirenz in 53% of the TDF group vs 25% of the no-TDF group) [7]. Label statement applies to the combination product.

Why yellow

The measured nutrient (25-hydroxyvitamin D) did not move, so no deficiency is shown; PTH and 1,25-dihydroxyvitamin D are hormones (Hard Rule 2). The functional-deficiency idea is testable (free calcitriol, PTH after vitamin D3) but was not confirmed in the sources opened. A second Tier A source [24] also shows no fall in 25-hydroxyvitamin D after starting a tenofovir/emtricitabine regimen (placebo arm +1.7 nmol/L), so the nutrient itself was measured in two cohorts without a decline.

Counter-evidence held on record

Counter-evidence on record 25-hydroxyvitamin D was not lower in TDF users [7] and did not fall over 48 weeks in the placebo arm of a randomized trial of efavirenz/emtricitabine/TDF initiation [24]. [7] is cross-sectional, adjusted, and the TDF group differed in efavirenz exposure; in [24] efavirenz was part of every participant's regimen, so efavirenz cannot be separated from the combination. Framing caution for the consumer surface Do not read this as vitamin D deficiency caused by the drug. The label text retrieved says vitamin D and calcium supplementation was not studied; a randomized trial since then reported less bone loss with supplementation during efavirenz/emtricitabine/TDF initiation [24], which is a bone-outcome result and not a dosing recommendation here. Any decision belongs with a prescriber.

Regulatory status

Truvada label sec 5.5: TDF was associated with slightly greater BMD decreases and higher bone turnover markers than comparators; iPrEx BMD substudy (n = 503) mean changes -0.4% to -1.0% across sites; 13% vs 6% lost at least 5% at the spine; fractures 1.7% vs 1.4% (iPrEx) and 0.8% vs 0.6% (Partners PrEP) [1][2]. Descovy label, DISCOVER: lumbar spine +0.5% (TAF) vs -1.1% (TDF), total hip +0.2% vs -1.0% [3].

Population evidence

iPrEx BMD substudy [11]: 498 participants (247 emtricitabine/TDF, 251 placebo); week 24 net spine change -0.91% (95% CI -1.44 to -0.38, p = 0.001), hip -0.61% (-0.96 to -0.27, p = 0.001); later intervals not significant; spine tended to recover after stopping; no fracture difference (p = 0.62). ASSERT [12]: 385 treatment-naive adults, tenofovir-emtricitabine vs abacavir-lamivudine, both with efavirenz; week 48 hip -3.6% vs -1.9% (p less than 0.001), spine -2.4% vs -1.6% (p = 0.036); loss of 6% or more at the hip in 13% vs 3% and at the spine in 15% vs 5%; bone turnover markers rose more with tenofovir-emtricitabine. Overton 2015, ACTG A5280 [24]: in 165 treatment-naive adults starting efavirenz/emtricitabine/TDF, total hip BMD change at 48 weeks was -3.22% (IQR -5.56 to -0.88) on placebo vs -1.36% (IQR -3.43 to 0.50) with vitamin D3 plus calcium (P = 0.004); lumbar spine similar; no hypercalcemia. This shows bone loss on the combination regimen, not that it was caused by a calcium or vitamin D shortfall; all participants also took efavirenz and had untreated HIV at baseline. Sax 2015 [13]: 1,733 adults on elvitegravir/cobicistat/emtricitabine plus TDF (867) or TAF (866); spine -2.86% vs -1.30%, hip -2.95% vs -0.66% (all p less than 0.0001).

Mechanism

Present: phosphate wasting with raised PTH and 1,25-dihydroxyvitamin D and osteomalacia from proximal tubulopathy (label) [1][2]. The raised PTH in [7] fits bone mineral mobilization, but serum calcium was unchanged [7].

Cohort test

Emtricitabine/TDF was in iPrEx [11], ASSERT [12] and the TDF arm of [13]. ASSERT's comparator is another drug (abacavir-lamivudine), so it does not test the combination against non-use; both arms lost bone.

Why yellow

Hard Rule 2: BMD and fracture are outcomes. No calcium or vitamin D deficiency was shown (serum calcium and 25-hydroxyvitamin D unchanged in [7]). Fracture rates were not significantly different from placebo in the PrEP trials [1][11].

Counter-evidence held on record

Counter-evidence on record Cooper 2010 found no association of TDF with fractures [10]. Efavirenz and HIV-related factors are competing explanations in treatment trials; in ASSERT both arms lost bone [12]. In iPrEx the loss occurred mainly in the first 24 weeks and then plateaued [11]. Framing caution for the consumer surface Bone density change is a drug effect on bone and kidney handling of phosphate, not proof of low calcium or vitamin D intake. The label notes supplementation was not studied; nothing here recommends a supplement.

Regulatory status

No carnitine statement in the retrieved Truvada label text [1][2].

Population evidence

Famularo 1997 [22]: non-randomized cross-sectional study; 12 HIV-positive patients with neuropathy on didanosine, zalcitabine or stavudine had significantly lower serum acetyl-carnitine than controls (didanosine n = 10 and zidovudine n = 11 without neuropathy, 10 HIV-negative neuropathy patients, 13 healthy); total carnitine did not differ. Figures reconstructed from an OpenAlex abstract index, so group sizes may be approximate.

Cohort test

FAILED for this drug: emtricitabine and tenofovir were not in the cohort (study predates both as HIV drugs). Tier C, capped at yellow.

Mechanism

Plausible but weak for this drug. The proposed route is nucleoside-analogue interference with mitochondrial DNA synthesis. The Truvada label describes both active metabolites only as weak inhibitors of mitochondrial polymerase gamma [2].

Why yellow

A real class-member study exists and the mechanism is at least plausible, so ungraded is not allowed. Search record: one Crossref bibliographic query on carnitine and nucleoside analogues returned older antiretroviral and pediatric studies; OpenAlex lookups of two of them returned no abstract. No study measuring carnitine in emtricitabine or tenofovir users was found.

Counter-evidence held on record

Counter-evidence on record No counter-evidence found in this drug. Crossref lookups for carnitine with nucleoside analogues returned older antiretroviral and children's studies; the children's study (2003) and a 2004 review had no retrievable abstract or drug list and are not used [22]. Framing caution for the consumer surface Not a finding that emtricitabine/tenofovir lowers carnitine. Do not suggest carnitine supplementation from this entry.