Drug · FAERS side-effect profile with label screen
Zidovudine side effects: what 13,295 FDA adverse event reports show
Drug class
Human Immunodeficiency Virus Nucleoside Analog Reverse Transcriptase Inhibitor
FDA label (Established Pharmacologic Class) · compare the class
Who reports
13,295 reports · 95% serious · 1,654 with death outcome · 45% female
openFDA FAERS counts, all years, deduplication not applied
Used for
Zidovudine tablets are a nucleoside analogue reverse transcriptase inhibitor indicated for: Treatment of Human Immunodeficiency Virus (HIV-1) infection in combination with other antiretroviral agents. (1.1) Prevention of maternal-fetal HIV-1 transmission.
FDA label, Indications and Usage
What it is
Zidovudine (formerly called azidothymidine [AZT]), a pyrimidine nucleoside analogue active against HIV-1.
FDA label, Description section
Boxed warning
RISK OF HEMATOLOGICAL TOXICITY, MYOPATHY, LACTIC ACIDOSIS AND SEVERE HEPATOMEGALY WITH STEATOSIS Zidovudine tablets have been associated with hematologic toxicity including neutropenia and severe anemia, particularly in patients with advanced HIV-1 disease [see Warnings and Precautions (5.1) ] .
FDA label
How to read this page. FAERS is a spontaneous-reporting system: counts are not incidence rates and a signal is not proof of causation.
Each reaction below is run through an automated screen — is the term in the FDA label (known), in the indications (the disease being treated), an administrative/coding term, or none of these (unlabeled)?
That screen is mechanical text matching, not a causality assessment. The 30 hand-written Bradford Hill assessments are on the causality assessment page. Not medical advice.
Causality screen of the 40 strongest signals
Labeled — boxed warning 1Labeled (related wording) 2Likely indication confounding 4Reporting / coding artifact 1Lab value / disease marker 4Not in label — unassessed 28
What the badges mean
- Labeled — boxed warning The term (or its clinical synonym) appears in the FDA boxed warning: causality is regulator-recognised and considered serious.
- Labeled (related wording) The label describes this effect under different wording (e.g. 'neutropenia' for 'neutrophil count decreased'). Treated as known.
- Likely indication confounding The term appears in the label's indications: reports probably describe the disease being treated (or its progression), not a drug effect. Classic confounding by indication.
- Reporting / coding artifact An administrative, monitoring or exposure term (product issue, off-label use, 'test normal', overdose...). Not a biological reaction; a high PRR here reflects how reports are coded.
- Lab value / disease marker A laboratory result, investigation or disease-activity marker (antibody positive, CRP abnormal, swollen joint count) not described in the label. These usually mirror the monitored disease or testing protocol rather than a drug effect; not screened further.
- Not in label — unassessed Not found in the label text, not an artifact pattern. This is a genuine candidate for a formal causality assessment (Bradford Hill / WHO-UMC); it has NOT had one here.
Strongest disproportionality signals
Flagged terms (PRR ≥ 2, χ² ≥ 4, n ≥ 10), ranked by PRR; infinite PRRs (no comparator reports) excluded. The EBGM column is a second, shrinkage-based estimate (MGPS) with its 5th percentile EB05 and the BCPNN IC025; a pair flagged by PRR alone is marked PRR-only and should be read as fragile. The strata column recomputes the PRR on serious reports only and flags pairs whose reports are unusually skewed by sex or come mostly from consumers rather than clinicians. 1,007 further terms are in the interactive explorer. Reaction links open the term's cross-drug page.
Show:
| Reaction | Reports | PRR 95% CI · ROR · χ²/p | EBGM EB05 · IC025 | Label screen | Serious-only & strata | Trial cross-check |
|---|---|---|---|---|---|---|
| Pinealoblastoma | 79 | 8,777.7 4,973.5–15,491.9ROR 8,830.2 · χ² 103,047 / p <1e-300 | 999.3 EB05 827.7 · IC025 +6.8 3/3 methods agree | Not in label — unassessed | serious n=79 · ♀ 0% (drug 45%) | no trial arm names this drug |
| Blood pyruvic acid decreased | 17 | 6,611.1 2,224.8–19,645.0ROR 6,619.5 · χ² 20,159 / p <1e-300 | 519.5 EB05 343.5 · IC025 +4.3 3/3 methods agree | Lab value / disease marker | serious n=17 | no trial arm names this drug |
| Congenital neoplasm | 21 | 5,444.4 2,197.8–13,487.1ROR 5,453.0 · χ² 24,202 / p <1e-300 | 573.9 EB05 396.0 · IC025 +4.6 3/3 methods agree | Not in label — unassessed | serious n=21 | no trial arm names this drug |
| Progressive external ophthalmoplegia | 100 | 5,363.9 3,549.0–8,107.0ROR 5,404.6 · χ² 119,337 / p <1e-300 | 978.7 EB05 828.0 · IC025 +7.1 3/3 methods agree | Not in label — unassessed | serious n=100 · ♀ 0% (drug 45%) · 93% clinician | no trial arm names this drug |
| Human immunodeficiency virus transmission | 147 | 2,078.8 1,624.6–2,659.9ROR 2,102.0 · χ² 129,780 / p <1e-300 | 797.2 EB05 694.8 · IC025 +7.5 3/3 methods agree | Likely indication confounding term in indications | serious n=147 · 100% clinician | no trial arm names this drug |
| Cloacal exstrophy | 31 | 1,722.2 1,033.4–2,870.0ROR 1,726.2 · χ² 24,497 / p <1e-300 | 542.5 EB05 400.3 · IC025 +5.3 3/3 methods agree | Not in label — unassessed | serious n=31 · 93% clinician | no trial arm names this drug |
| Lactate pyruvate ratio increased | 24 | 1,697.0 951.8–3,025.6ROR 1,700.0 · χ² 18,652 / p <1e-300 | 492.0 EB05 348.0 · IC025 +4.8 3/3 methods agree | Lab value / disease marker | serious n=24 | no trial arm names this drug |
| Ultrasound antenatal screen | 49 | 1,693.8 1,130.5–2,537.8ROR 1,700.1 · χ² 38,879 / p <1e-300 | 615.2 EB05 483.7 · IC025 +6.0 3/3 methods agree | Not in label — unassessed | serious n=49 · 100% clinician | no trial arm names this drug |
| Congenital hiv infection | 20 | 1,637.4 874.1–3,067.3ROR 1,639.9 · χ² 15,147 / p <1e-300 | 451.8 EB05 308.8 · IC025 +4.5 3/3 methods agree | Not in label — unassessed | serious n=20 | no trial arm names this drug |
| Retroperitoneal disorder | 10 | 1,414.1 600.7–3,329.2ROR 1,415.2 · χ² 6,675 / p <1e-300 | 306.6 EB05 178.0 · IC025 +3.3 3/3 methods agree | Not in label — unassessed | serious n=10 | no trial arm names this drug |
| Bladder agenesis | 32 | 1,185.2 748.5–1,876.6ROR 1,188.0 · χ² 20,822 / p <1e-300 | 479.3 EB05 355.5 · IC025 +5.3 3/3 methods agree | Not in label — unassessed | serious n=32 · 93% clinician | no trial arm names this drug |
| Csf hiv escape syndrome | 55 | 1,030.8 733.4–1,448.7ROR 1,035.1 · χ² 33,415 / p <1e-300 | 509.8 EB05 406.4 · IC025 +6.1 3/3 methods agree | Not in label — unassessed | serious n=55 · 100% clinician | no trial arm names this drug |
| Peritoneal thickening | 10 | 864.2 399.0–1,871.8ROR 864.8 · χ² 5,001 / p <1e-300 | 269.7 EB05 156.6 · IC025 +3.3 3/3 methods agree | Not in label — unassessed | serious n=10 | no trial arm names this drug |
| Blood pyruvic acid increased | 16 | 802.9 439.3–1,467.5ROR 803.8 · χ² 7,931 / p <1e-300 | 324.3 EB05 211.6 · IC025 +4.1 3/3 methods agree | Lab value / disease marker | serious n=16 | no trial arm names this drug |
| Mitochondrial toxicity | 240 | 652.7 561.9–758.1ROR 664.7 · χ² 109,552 / p <1e-300 | 443.7 EB05 398.6 · IC025 +7.7 3/3 methods agree | Not in label — unassessed | serious n=239 · ♀ 9% (drug 45%) | no trial arm names this drug |
| Gastrointestinal disorder congenital | 28 | 565.7 367.2–871.5ROR 566.8 · χ² 11,163 / p <1e-300 | 323.3 EB05 234.7 · IC025 +5.0 3/3 methods agree | Not in label — unassessed | serious n=28 · 100% clinician | no trial arm names this drug |
| Aids encephalopathy | 15 | 542.6 301.5–976.5ROR 543.2 · χ² 5,617 / p <1e-300 | 266.2 EB05 171.2 · IC025 +4.0 3/3 methods agree | Not in label — unassessed | serious n=15 | no trial arm names this drug |
| Genitalia external ambiguous | 44 | 530.6 377.0–746.7ROR 532.3 · χ² 16,949 / p <1e-300 | 337.7 EB05 261.9 · IC025 +5.7 3/3 methods agree | Not in label — unassessed | serious n=44 · 90% clinician | no trial arm names this drug |
| Astrocytoma malignant | 24 | 525.8 331.1–835.0ROR 526.8 · χ² 9,007 / p <1e-300 | 299.4 EB05 211.7 · IC025 +4.8 3/3 methods agree | Not in label — unassessed | serious n=24 | no trial arm names this drug |
| Meconium stain | 38 | 509.6 353.4–734.8ROR 511.0 · χ² 14,148 / p <1e-300 | 321.8 EB05 244.7 · IC025 +5.5 3/3 methods agree | Not in label — unassessed | serious n=38 · 94% clinician | no trial arm names this drug |
| Immune reconstitution syndrome | 303 | 477.1 419.9–542.0ROR 488.2 · χ² 109,801 / p <1e-300 | 357.1 EB05 324.6 · IC025 +7.6 3/3 methods agree | Labeled — boxed warning exact term | serious n=300 | no trial arm names this drug |
| Congenital ectopic bladder | 11 | 475.3 242.0–933.5ROR 475.7 · χ² 3,633 / p <1e-300 | 223.4 EB05 133.1 · IC025 +3.4 3/3 methods agree | Not in label — unassessed | serious n=11 | no trial arm names this drug |
| Vertical infection transmission | 26 | 470.3 303.4–729.0ROR 471.2 · χ² 8,992 / p <1e-300 | 285.5 EB05 204.7 · IC025 +4.9 3/3 methods agree | Labeled (related wording) related wording | serious n=26 | no trial arm names this drug |
| Neutropenia neonatal | 51 | 461.2 337.6–630.1ROR 463.0 · χ² 17,711 / p <1e-300 | 314.0 EB05 248.1 · IC025 +5.9 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=50 | no trial arm names this drug |
| Hiv-associated neurocognitive disorder | 23 | 406.6 257.0–643.2ROR 407.3 · χ² 7,059 / p <1e-300 | 254.4 EB05 178.6 · IC025 +4.7 3/3 methods agree | Not in label — unassessed | serious n=23 | no trial arm names this drug |
| Lipodystrophy acquired | 436 | 406.1 366.0–450.6ROR 419.9 · χ² 139,412 / p <1e-300 | 317.8 EB05 293.5 · IC025 +7.7 3/3 methods agree | Not in label — unassessed | serious n=433 · ♀ 19% (drug 45%) | no trial arm names this drug |
| Tuberculoid leprosy | 13 | 388.9 211.8–714.0ROR 389.3 · χ² 3,719 / p <1e-300 | 213.9 EB05 133.0 · IC025 +3.7 3/3 methods agree | Not in label — unassessed | serious n=11 | no trial arm names this drug |
| Caudal regression syndrome | 30 | 370.4 248.8–551.3ROR 371.2 · χ² 8,630 / p <1e-300 | 251.5 EB05 184.6 · IC025 +5.1 3/3 methods agree | Not in label — unassessed | serious n=30 · 93% clinician | no trial arm names this drug |
| Congenital naevus | 25 | 353.5 229.1–545.6ROR 354.2 · χ² 6,876 / p <1e-300 | 236.3 EB05 168.3 · IC025 +4.8 3/3 methods agree | Not in label — unassessed | serious n=25 | no trial arm names this drug |
| Alpha 1 foetoprotein abnormal | 18 | 341.5 205.1–568.6ROR 341.9 · χ² 4,735 / p <1e-300 | 216.1 EB05 144.7 · IC025 +4.2 3/3 methods agree | Lab value / disease marker | serious n=12 | no trial arm names this drug |
| Hiv viraemia | 36 | 329.4 230.0–471.8ROR 330.3 · χ² 9,458 / p <1e-300 | 237.8 EB05 179.4 · IC025 +5.3 3/3 methods agree | Not in label — unassessed | serious n=36 · 100% clinician | no trial arm names this drug |
| Aids dementia complex | 10 | 305.0 154.9–600.6ROR 305.2 · χ² 2,285 / p <1e-300 | 172.1 EB05 99.9 · IC025 +3.2 3/3 methods agree | Not in label — unassessed | serious n=10 | no trial arm names this drug |
| Anaemia neonatal | 77 | 298.7 234.2–381.0ROR 300.4 · χ² 18,917 / p <1e-300 | 236.1 EB05 195.0 · IC025 +6.2 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=77 | no trial arm names this drug |
| Congenital genital malformation | 25 | 288.1 188.1–441.2ROR 288.6 · χ² 5,794 / p <1e-300 | 205.2 EB05 146.2 · IC025 +4.7 3/3 methods agree | Not in label — unassessed | serious n=25 · 91% clinician | no trial arm names this drug |
| Viral mutation identified | 568 | 285.4 261.4–311.6ROR 298.1 · χ² 135,795 / p <1e-300 | 239.4 EB05 223.3 · IC025 +7.5 3/3 methods agree | Not in label — unassessed | serious n=568 · 97% clinician | no trial arm names this drug |
| Aids related complication | 10 | 282.8 144.2–554.7ROR 283.0 · χ² 2,144 / p <1e-300 | 164.8 EB05 95.7 · IC025 +3.2 3/3 methods agree | Reporting / coding artifact | serious n=10 | no trial arm names this drug |
| Virologic failure | 816 | 281.4 261.7–302.6ROR 299.8 · χ² 192,906 / p <1e-300 | 237.2 EB05 223.8 · IC025 +7.6 3/3 methods agree | Labeled (related wording) related wording | serious n=816 · 99% clinician | no trial arm names this drug |
| Congenital teratoma | 13 | 280.9 155.6–506.9ROR 281.1 · χ² 2,838 / p <1e-300 | 176.7 EB05 109.9 · IC025 +3.7 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=13 | no trial arm names this drug |
| Tethered cord syndrome | 31 | 253.8 173.7–370.9ROR 254.4 · χ² 6,495 / p <1e-300 | 192.6 EB05 142.1 · IC025 +5.0 3/3 methods agree | Not in label — unassessed | serious n=31 · 100% clinician | no trial arm names this drug |
| Trisomy 18 | 51 | 241.9 180.2–324.7ROR 242.8 · χ² 10,380 / p <1e-300 | 194.3 EB05 153.5 · IC025 +5.6 3/3 methods agree | Not in label — unassessed | serious n=50 · 100% clinician | no trial arm names this drug |
Trial evidence (ClinicalTrials.gov)
ClinicalTrials.gov returned results-bearing trials mentioning Zidovudine only as a background or rescue medication (NCT01061151, NCT00074581); no trial listing it as the tested intervention was cached, so no trial cross-check is shown.
Most frequently reported reactions
By raw co-report count, regardless of disproportionality. Common terms here are often the illness itself or generic outcomes.
| Reaction | Reports | PRR 95% CI · ROR · χ²/p | EBGM EB05 · IC025 | Label screen | Serious-only & strata | Trial cross-check |
|---|---|---|---|---|---|---|
| Foetal exposure during pregnancy | 2,144 | 42.7 41.1–44.5ROR 50.8 · χ² 85,350 / p <1e-300 | 41.6 EB05 40.2 · IC025 +5.3 3/3 methods agree | Reporting / coding artifact | serious PRR 25.4 | no trial arm names this drug |
| Drug exposure during pregnancy | 1,075 | 50.7 47.8–53.8ROR 55.1 · χ² 50,775 / p <1e-300 | 49.1 EB05 46.7 · IC025 +5.5 3/3 methods agree | Reporting / coding artifact | serious PRR 31.9 | no trial arm names this drug |
| Anaemia (low red blood cells) | 935 | 7.8 7.3–8.3ROR 8.3 · χ² 5,523 / p <1e-300 | 7.7 EB05 7.3 · IC025 +2.8 3/3 methods agree | Labeled — boxed warning exact term | serious PRR 5.1 | no trial arm names this drug |
| Virologic failure | 816 | 281.4 261.7–302.6ROR 299.8 · χ² 192,906 / p <1e-300 | 237.2 EB05 223.8 · IC025 +7.6 3/3 methods agree | Labeled (related wording) related wording | serious n=816 · 99% clinician | no trial arm names this drug |
| Drug resistance | 732 | 46.3 43.1–49.7ROR 48.9 · χ² 31,470 / p <1e-300 | 44.9 EB05 42.2 · IC025 +5.3 3/3 methods agree | Reporting / coding artifact | serious PRR 30.3 · 95% clinician | no trial arm names this drug |
| Premature baby | 722 | 38.6 35.9–41.5ROR 40.8 · χ² 25,823 / p <1e-300 | 37.7 EB05 35.4 · IC025 +5.1 3/3 methods agree | Not in label — unassessed | serious PRR 22.7 | no trial arm names this drug |
| Exposure during pregnancy | 651 | 16.7 15.5–18.0ROR 17.5 · χ² 9,506 / p <1e-300 | 16.5 EB05 15.5 · IC025 +3.9 3/3 methods agree | Reporting / coding artifact | serious PRR 12.0 · ♀ 95% (drug 45%) | no trial arm names this drug |
| Pathogen resistance | 599 | 111.1 102.5–120.5ROR 116.3 · χ² 60,942 / p <1e-300 | 103.5 EB05 96.7 · IC025 +6.4 3/3 methods agree | Reporting / coding artifact | serious PRR 66.3 · 97% clinician | no trial arm names this drug |
| Viral mutation identified | 568 | 285.4 261.4–311.6ROR 298.1 · χ² 135,795 / p <1e-300 | 239.4 EB05 223.3 · IC025 +7.5 3/3 methods agree | Not in label — unassessed | serious n=568 · 97% clinician | no trial arm names this drug |
| Maternal exposure during pregnancy | 520 | 9.3 8.6–10.2ROR 9.7 · χ² 3,862 / p <1e-300 | 9.3 EB05 8.6 · IC025 +3.1 3/3 methods agree | Reporting / coding artifact | serious PRR 5.0 · ♀ 96% (drug 45%) | no trial arm names this drug |
| Pyrexia (fever) | 471 | 2.1 2.0–2.3ROR 2.2 · χ² 292 / p 9e-66 | 2.1 EB05 2.0 · IC025 +0.9 | Labeled (related wording) related wording | serious PRR 1.6 | no trial arm names this drug |
| Lipodystrophy acquired | 436 | 406.1 366.0–450.6ROR 419.9 · χ² 139,412 / p <1e-300 | 317.8 EB05 293.5 · IC025 +7.7 3/3 methods agree | Not in label — unassessed | serious n=433 · ♀ 19% (drug 45%) | no trial arm names this drug |
| Pain | 427 | 1.1 1.0–1.2ROR 1.1 · χ² 4 / p 0.031 | 1.1 EB05 1.0 · IC025 -0.0 PRR-only: not supported by EBGM or IC | Labeled adverse reaction exact term | serious PRR 1.0 | no trial arm names this drug |
| Treatment failure | 423 | 8.2 7.4–9.0ROR 8.4 · χ² 2,649 / p <1e-300 | 8.1 EB05 7.4 · IC025 +2.9 3/3 methods agree | Reporting / coding artifact | serious PRR 9.4 · 99% clinician | no trial arm names this drug |
| Death | 418 | 0.8 0.7–0.8ROR 0.8 · χ² 31 / p 1e-8 | 0.8 EB05 0.7 · IC025 -0.5 PRR-only: not supported by EBGM or IC | Outcome field, not a reaction boxed warning mentions mortality | serious PRR 0.5 | no trial arm names this drug |
Unlabeled candidate signals
These flagged terms were not found in the FDA label text and do not match an artifact pattern. They are the pairs that would merit a structured assessment (temporality, dose-response, biological plausibility, consistency across databases, trial or cohort evidence). The screen has not done that; string-matching misses label wording, and a strong PRR can still be stimulated reporting, co-medication, or the disease itself.
- Pinealoblastoma — n=79, PRR 8,777.7
- Congenital neoplasm — n=21, PRR 5,444.4
- Progressive external ophthalmoplegia — n=100, PRR 5,363.9
- Cloacal exstrophy — n=31, PRR 1,722.2
- Ultrasound antenatal screen — n=49, PRR 1,693.8
- Congenital hiv infection — n=20, PRR 1,637.4
- Bladder agenesis — n=32, PRR 1,185.2
- Csf hiv escape syndrome — n=55, PRR 1,030.8
- Mitochondrial toxicity — n=240, PRR 652.7
- Gastrointestinal disorder congenital — n=28, PRR 565.7
✓ A hand-written Bradford Hill causality assessment exists for this drug: Zidovudine ↔ Anaemia / bone-marrow suppression.
Want to assess one of these properly? The runbook describes the Bradford Hill / trial-evidence workflow used on the assessment page, and handoff_top1000_signals.csv lists the strongest unassessed pairs across all drugs.
Common questions
What are the most reported side effects of Zidovudine?
In FDA FAERS, the most frequently co-reported reaction terms for Zidovudine are anaemia, virologic failure, premature baby, viral mutation identified, pyrexia, lipodystrophy acquired. These are report counts, not rates: FAERS has no denominator, reporting is voluntary and uneven, and a term can be reported because of the illness being treated rather than the drug.
Does Zidovudine have an FDA boxed warning?
Yes. The current FDA label carries a boxed warning: RISK OF HEMATOLOGICAL TOXICITY, MYOPATHY, LACTIC ACIDOSIS AND SEVERE HEPATOMEGALY WITH STEATOSIS Zidovudine tablets have been associated with hematologic toxicity including neutropenia and severe anemia, particularly in patients with advanced HIV-1 disease [see Warnings and Precautions (5.1) ] .
Do FAERS signals prove that Zidovudine causes these side effects?
No. A disproportionality signal (PRR, ROR) means a reaction is reported more often with this drug than with others in the database. That can reflect a real effect, but also the disease being treated, stimulated reporting after news or litigation, co-medications, or how reports are coded. Causality needs temporality, dose-response, biological plausibility, consistency across data sources and, ideally, trial or cohort evidence. This page screens each term against the FDA label and ClinicalTrials.gov results; it does not establish causation.
Sources & methods
- FDA label via openFDA (set ID e7c8ddef-005d-4f1c-8c1a-ea84044ab4d4, effective 20240125; matched on
openfda.generic_name.exact:"ZIDOVUDINE") - Bayesian shrinkage measures computed offline over all 1,317,300 cached pairs: BCPNN information component (IC, with Norén closed-form IC025) and MGPS empirical-Bayes geometric mean (EBGM, EB05) with a two-component gamma prior fitted by maximum marginal likelihood (α₁=0.57, β₁=0.02, α₂=1.42, β₂=0.70, w=0.17); unstratified
- FAERS pair statistics from the OpenPV build of 2026-09-14 (openFDA
count=aggregation, fieldpatient.drug.openfda.generic_name.exact, 1,047 reaction terms, min 3 co-reports); PRR/ROR with 95% CI, chi-square with Yates correction - Serious-only and stratified counts (serious:1, patient.patientsex, primarysource.qualification) from openFDA count queries; serious-only PRR uses the drug serious report total and the term global serious total (N_serious=11,882,979); strata shown only when n ≥ 20
- Seriousness and sex counts from openFDA
count=serious,patient.patientsex,seriousnessdeath - ClinicalTrials.gov API v2 (query
ZIDOVUDINE, results-bearing studies sorted by enrollment)
Page generated 2026-10-08. Label and PubChem text are retrieved automatically and may lag the current label; always check the current prescribing information. OpenPV is a beta research tool of the Open Source Medicine Foundation.