Isoniazid side effects: what 16,105 FDA adverse event reports show
Who reports
16,105 reports · 91% serious · 2,199 with death outcome · 50% female
Used for
Isoniazid is recommended for all forms of tuberculosis in which organisms are susceptible. However, active tuberculosis must be treated with multiple concomitant anti-tuberculosis medications to prevent the emergence of drug resistance. Single-drug treatment of active tuberculosis with isoniazid, or any other medication is inadequate therapy.
What it is
DESCRIPTION Isoniazid is an antibacterial available as 100 mg and 300 mg tablets for oral administration.
Boxed warning
Severe and sometimes fatal hepatitis associated with isoniazid therapy has been reported and may occur or may develop even after many months of treatment. The risk of developing hepatitis is age related. Approximate .
Causality screen of the 40 strongest signals
What the badges mean
- 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.
- 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. 1,088 further terms are in the interactive explorer. Reaction links open the term's cross-drug page.
| Reaction | Reports | PRR 95% CI · ROR · χ²/p | EBGM EB05 · IC025 | Label screen | Serious-only & strata | Trial cross-check |
|---|---|---|---|---|---|---|
| Tuberculoma of central nervous system | 98 | 1,515.7 1,131.9–2,029.6ROR 1,525.0 · χ² 67,332 / p <1e-300 | 611.9 EB05 516.8 · IC025 +6.9 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=98 · 97% clinician | not reported in cached trials |
| Serpiginous choroiditis | 24 | 1,283.7 729.2–2,259.9ROR 1,285.6 · χ² 14,745 / p <1e-300 | 424.3 EB05 300.1 · IC025 +4.8 3/3 methods agree | Not in label — unassessed | serious n=24 · ♀ 26% (drug 50%) · 100% clinician | not reported in cached trials |
| Immune reconstitution inflammatory syndrome associated tuberculosis | 162 | 1,245.3 1,003.8–1,544.9ROR 1,257.9 · χ² 101,606 / p <1e-300 | 588.4 EB05 516.2 · IC025 +7.5 3/3 methods agree | Labeled (related wording) related wording | serious n=162 · 97% clinician | not reported in cached trials |
| Vaginal flatulence | 89 | 536.4 419.0–686.6ROR 539.4 · χ² 33,168 / p <1e-300 | 350.1 EB05 293.2 · IC025 +6.6 3/3 methods agree | Not in label — unassessed | serious n=89 · ♀ 100% (drug 50%) | not reported in cached trials |
| Tuberculosis of eye | 18 | 453.1 264.8–775.2ROR 453.6 · χ² 5,672 / p <1e-300 | 247.3 EB05 165.5 · IC025 +4.3 3/3 methods agree | Likely indication confounding term in indications; also in warnings | serious n=18 | NCT01404312: 1/1,504 (0.1%) on Isoniazid (serious AE) |
| Tuberculosis of central nervous system | 55 | 339.4 252.3–456.7ROR 340.6 · χ² 14,412 / p <1e-300 | 245.8 EB05 195.9 · IC025 +5.9 3/3 methods agree | Labeled (related wording) related wording | serious n=55 | not reported in cached trials |
| Interferon gamma release assay positive | 34 | 338.3 231.9–493.5ROR 339.1 · χ² 8,785 / p <1e-300 | 233.0 EB05 174.4 · IC025 +5.2 3/3 methods agree | Lab value / disease marker | serious n=34 | not reported in cached trials |
| Pyelonephritis fungal | 12 | 256.7 138.2–477.1ROR 256.9 · χ² 2,339 / p <1e-300 | 160.1 EB05 97.6 · IC025 +3.5 3/3 methods agree | Not in label — unassessed | serious n=12 | not reported in cached trials |
| Meningitis tuberculous | 92 | 254.5 203.6–318.2ROR 256.0 · χ² 19,178 / p <1e-300 | 203.6 EB05 171.0 · IC025 +6.3 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=92 · 91% clinician | not reported in cached trials |
| Diaphragmatic injury | 12 | 252.5 136.0–468.9ROR 252.7 · χ² 2,306 / p <1e-300 | 158.5 EB05 96.6 · IC025 +3.5 3/3 methods agree | Not in label — unassessed | serious n=12 | not reported in cached trials |
| Paradoxical drug reaction | 554 | 231.7 211.9–253.3ROR 239.9 · χ² 107,603 / p <1e-300 | 195.1 EB05 181.8 · IC025 +7.2 3/3 methods agree | Not in label — unassessed | serious n=547 · 99% clinician | not reported in cached trials |
| Demodicidosis | 13 | 214.0 119.0–384.8ROR 214.1 · χ² 2,183 / p <1e-300 | 144.9 EB05 90.1 · IC025 +3.6 3/3 methods agree | Not in label — unassessed | serious n=10 | not reported in cached trials |
| Haemodilution | 13 | 196.3 109.5–351.9ROR 196.5 · χ² 2,025 / p <1e-300 | 136.7 EB05 85.0 · IC025 +3.6 3/3 methods agree | Not in label — unassessed | serious n=13 | not reported in cached trials |
| Tuberculosis of genitourinary system | 11 | 190.8 101.3–359.4ROR 191.0 · χ² 1,647 / p <1e-300 | 129.5 EB05 77.2 · IC025 +3.3 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=11 | not reported in cached trials |
| Nicotinic acid deficiency | 14 | 185.3 105.8–324.4ROR 185.4 · χ² 2,084 / p <1e-300 | 133.1 EB05 84.2 · IC025 +3.7 3/3 methods agree | Not in label — unassessed | serious n=10 | not reported in cached trials |
| Hemianopia heteronymous | 10 | 180.8 93.3–350.5ROR 180.9 · χ² 1,414 / p <1e-300 | 122.3 EB05 71.0 · IC025 +3.1 3/3 methods agree | Not in label — unassessed | serious n=10 | not reported in cached trials |
| Tuberculosis skin test positive | 10 | 178.3 92.0–345.4ROR 178.4 · χ² 1,396 / p <1e-300 | 121.1 EB05 70.3 · IC025 +3.1 3/3 methods agree | Likely indication confounding term in indications | – | not reported in cached trials |
| Pericarditis tuberculous | 11 | 158.7 84.8–296.8ROR 158.8 · χ² 1,397 / p <1e-300 | 113.9 EB05 67.9 · IC025 +3.3 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=11 | not reported in cached trials |
| Tuberculosis gastrointestinal | 34 | 156.4 109.6–223.3ROR 156.8 · χ² 4,543 / p <1e-300 | 129.6 EB05 97.0 · IC025 +5.0 3/3 methods agree | Likely indication confounding term in indications; also in warnings | serious n=34 · 94% clinician | not reported in cached trials |
| Sideroblastic anaemia | 14 | 142.6 82.1–247.7ROR 142.8 · χ² 1,647 / p <1e-300 | 109.7 EB05 69.4 · IC025 +3.7 3/3 methods agree | Labeled (related wording) related wording | serious n=14 | not reported in cached trials |
| Splenic embolism | 11 | 141.2 75.8–263.1ROR 141.3 · χ² 1,256 / p 2e-275 | 104.7 EB05 62.4 · IC025 +3.3 3/3 methods agree | Not in label — unassessed | serious n=11 | not reported in cached trials |
| Acid fast bacilli infection | 15 | 136.6 80.2–232.5ROR 136.7 · χ² 1,704 / p <1e-300 | 107.1 EB05 68.9 · IC025 +3.8 3/3 methods agree | Not in label — unassessed | serious n=15 | not reported in cached trials |
| Peritoneal tuberculosis | 39 | 128.0 92.2–177.9ROR 128.4 · χ² 4,355 / p <1e-300 | 110.4 EB05 84.2 · IC025 +5.0 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=39 · 94% clinician | not reported in cached trials |
| Immune reconstitution syndrome | 116 | 126.7 104.8–153.3ROR 127.6 · χ² 13,056 / p <1e-300 | 113.3 EB05 97.0 · IC025 +6.0 3/3 methods agree | Not in label — unassessed | serious n=115 | not reported in cached trials |
| Choroiditis | 33 | 125.3 87.7–179.1ROR 125.6 · χ² 3,596 / p <1e-300 | 107.3 EB05 80.0 · IC025 +4.8 3/3 methods agree | Not in label — unassessed | serious n=33 · 100% clinician | not reported in cached trials |
| Intestinal tuberculosis | 15 | 121.1 71.3–205.6ROR 121.2 · χ² 1,525 / p <1e-300 | 97.4 EB05 62.6 · IC025 +3.7 3/3 methods agree | Likely indication confounding term in indications; also in warnings | serious n=15 | not reported in cached trials |
| Extrapulmonary tuberculosis | 25 | 119.7 79.5–180.4ROR 119.9 · χ² 2,585 / p <1e-300 | 101.3 EB05 72.2 · IC025 +4.5 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=25 | not reported in cached trials |
| Disseminated tuberculosis | 207 | 115.2 100.0–132.7ROR 116.7 · χ² 21,408 / p <1e-300 | 104.8 EB05 93.4 · IC025 +6.2 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=206 · 94% clinician | NCT01404312: 2/1,504 (0.1%) on Isoniazid (serious AE) |
| Lymph node tuberculosis | 60 | 114.3 87.8–148.7ROR 114.7 · χ² 6,083 / p <1e-300 | 101.7 EB05 81.9 · IC025 +5.4 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=60 · 95% clinician | not reported in cached trials |
| Disseminated bacillus calmette-guerin infection | 36 | 108.5 77.2–152.4ROR 108.7 · χ² 3,437 / p <1e-300 | 95.2 EB05 71.8 · IC025 +4.9 3/3 methods agree | Not in label — unassessed | serious n=36 · ♀ 0% (drug 50%) · 100% clinician | not reported in cached trials |
| Cutaneous tuberculosis | 14 | 107.0 62.0–184.5ROR 107.1 · χ² 1,261 / p 2e-276 | 87.4 EB05 55.3 · IC025 +3.6 3/3 methods agree | Labeled (related wording) related wording | serious n=14 | not reported in cached trials |
| Bone tuberculosis | 28 | 102.7 69.9–150.9ROR 102.9 · χ² 2,518 / p <1e-300 | 89.5 EB05 65.0 · IC025 +4.5 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=28 · ♀ 24% (drug 50%) | NCT01404312: 1/1,504 (0.1%) on Isoniazid (serious AE) |
| Tuberculous pleurisy | 34 | 100.1 70.6–141.9ROR 100.3 · χ² 3,003 / p <1e-300 | 88.5 EB05 66.2 · IC025 +4.7 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=33 · 94% clinician | not reported in cached trials |
| Thalassaemia | 12 | 97.5 54.2–175.3ROR 97.6 · χ² 977 / p 8e-215 | 79.6 EB05 48.5 · IC025 +3.3 3/3 methods agree | Not in label — unassessed | serious n=12 | not reported in cached trials |
| Mycobacterium kansasii infection | 11 | 92.3 50.1–170.1ROR 92.4 · χ² 843 / p 1e-185 | 75.3 EB05 44.9 · IC025 +3.2 3/3 methods agree | Not in label — unassessed | serious n=11 | not reported in cached trials |
| Pulmonary tuberculosis | 282 | 92.2 81.8–103.9ROR 93.8 · χ² 23,645 / p <1e-300 | 85.6 EB05 77.5 · IC025 +6.0 3/3 methods agree | Likely indication confounding term in indications | serious n=281 | not reported in cached trials |
| Hepatic haematoma | 31 | 90.2 62.7–129.8ROR 90.4 · χ² 2,473 / p <1e-300 | 80.3 EB05 59.3 · IC025 +4.6 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=31 · ♀ 100% (drug 50%) | not reported in cached trials |
| Gingivitis ulcerative | 13 | 85.1 48.6–149.2ROR 85.2 · χ² 936 / p 6e-206 | 71.8 EB05 44.7 · IC025 +3.4 3/3 methods agree | Not in label — unassessed | serious n=13 | not reported in cached trials |
| Congestive hepatopathy | 26 | 80.8 54.4–120.1ROR 80.9 · χ² 1,854 / p <1e-300 | 72.2 EB05 51.8 · IC025 +4.3 3/3 methods agree | Not in label — unassessed | serious n=26 · ♀ 100% (drug 50%) | not reported in cached trials |
| Immune reconstitution inflammatory syndrome | 283 | 78.0 69.2–87.8ROR 79.4 · χ² 20,210 / p <1e-300 | 73.2 EB05 66.3 · IC025 +5.8 3/3 methods agree | Not in label — unassessed | serious n=283 · 97% clinician | not reported in cached trials |
Trial evidence (ClinicalTrials.gov)
✓ Trial adverse-event data found on ClinicalTrials.gov
Largest completed trials with posted results that list Isoniazid as a study intervention. The right-hand column of the signal table shows whether each FAERS term was also recorded in these trials, with a real denominator (3 of 40 signal terms matched).
- NCT00023452 — Three Months of Weekly Rifapentine and Isoniazid for M. Tuberculosis Infection (N=8053, PHASE3; 130 AE terms posted; arms: 9INH; 3RPT/INH)
- NCT01404312 — Brief Rifapentine-Isoniazid Evaluation for TB Prevention (BRIEF TB) (N=3000, PHASE3; 101 AE terms posted; arms: RPT Plus INH Regimen (Arm A); INH Regimen (Arm B))
Caveats: trial populations, doses and follow-up differ from the reporting population; AE terms are sponsor-coded and matched here by wording; absence from a trial list means the term was not reported above the sponsor's frequency threshold, not that it cannot occur.
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 |
|---|---|---|---|---|---|---|
| Drug ineffective (drug did not work) | 1,183 | 1.2 1.1–1.2ROR 1.2 · χ² 31 / p 1e-8 | 1.2 EB05 1.1 · IC025 +0.1 | Reporting / coding artifact | serious PRR 2.0 | not reported in cached trials |
| Pyrexia (fever) | 1,102 | 4.2 3.9–4.4ROR 4.4 · χ² 2,671 / p <1e-300 | 4.1 EB05 3.9 · IC025 +1.9 3/3 methods agree | Labeled — boxed warning synonym match | serious PRR 3.2 | NCT00023452: 1/4,040 (0.0%) on Isoniazid (serious AE) |
| Drug interaction | 935 | 7.7 7.2–8.2ROR 8.1 · χ² 5,464 / p <1e-300 | 7.6 EB05 7.2 · IC025 +2.8 3/3 methods agree | Reporting / coding artifact | serious PRR 5.3 · 96% clinician | not reported in cached trials |
| Nausea | 903 | 1.5 1.4–1.6ROR 1.5 · χ² 151 / p 6e-35 | 1.5 EB05 1.4 · IC025 +0.5 | Labeled — boxed warning exact term | serious PRR 1.6 · ♀ 70% (drug 50%) | NCT00023452: 1/3,759 (0.0%) on Isoniazid (serious AE) |
| Drug-induced liver injury | 862 | 37.4 35.0–40.0ROR 39.5 · χ² 29,692 / p <1e-300 | 36.4 EB05 34.4 · IC025 +5.0 3/3 methods agree | Labeled (related wording) related wording | serious PRR 23.0 · 95% clinician | NCT01404312: 1/1,496 (0.1%) on Isoniazid (serious AE) |
| Off label use (used outside approved label) | 860 | 1.3 1.2–1.4ROR 1.3 · χ² 58 / p 1e-14 | 1.3 EB05 1.2 · IC025 +0.3 | Reporting / coding artifact | serious PRR 1.4 | not reported in cached trials |
| Drug reaction with eosinophilia and systemic symptoms | 744 | 39.0 36.3–41.9ROR 40.9 · χ² 26,748 / p <1e-300 | 37.9 EB05 35.6 · IC025 +5.1 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 24.0 · 98% clinician | not reported in cached trials |
| Vomiting | 636 | 1.8 1.6–1.9ROR 1.8 · χ² 216 / p 4e-49 | 1.8 EB05 1.7 · IC025 +0.7 | Labeled — boxed warning exact term | serious PRR 1.6 | NCT00023452: 2/3,759 (0.1%) on Isoniazid (serious AE) |
| Headache | 614 | 1.3 1.2–1.4ROR 1.3 · χ² 38 / p 4e-10 | 1.3 EB05 1.2 · IC025 +0.2 | Not in label — unassessed | serious PRR 1.5 · ♀ 77% (drug 50%) | NCT01404312: 155/1,496 (10.4%) on Isoniazid |
| Paradoxical drug reaction | 554 | 231.7 211.9–253.3ROR 239.9 · χ² 107,603 / p <1e-300 | 195.1 EB05 181.8 · IC025 +7.2 3/3 methods agree | Not in label — unassessed | serious n=547 · 99% clinician | not reported in cached trials |
| Tuberculosis | 547 | 57.8 53.1–62.9ROR 59.8 · χ² 29,188 / p <1e-300 | 55.3 EB05 51.5 · IC025 +5.6 3/3 methods agree | Labeled — boxed warning exact term | serious PRR 35.4 | NCT01404312: 1/1,504 (0.1%) on Isoniazid (serious AE) |
| Arthralgia (joint pain) | 546 | 1.7 1.6–1.9ROR 1.7 · χ² 166 / p 3e-38 | 1.7 EB05 1.6 · IC025 +0.6 | Not in label — unassessed | serious PRR 1.8 · ♀ 75% (drug 50%) | not reported in cached trials |
| Condition aggravated | 508 | 2.2 2.0–2.4ROR 2.2 · χ² 332 / p 1e-74 | 2.2 EB05 2.0 · IC025 +1.0 3/3 methods agree | Reporting / coding artifact | serious PRR 2.1 · 92% clinician | not reported in cached trials |
| Rash | 507 | 1.5 1.4–1.7ROR 1.5 · χ² 92 / p 4e-22 | 1.5 EB05 1.4 · IC025 +0.5 | Labeled — boxed warning exact term | serious PRR 1.9 | NCT01404312: 2/1,496 (0.1%) on Isoniazid (serious AE) |
| Diarrhoea (diarrhea) | 506 | 1.0 0.9–1.1ROR 1.0 · χ² 0 / p 0.301 | 1.0 EB05 1.0 · IC025 -0.1 PRR-only: not supported by EBGM or IC | Not in label — unassessed | serious PRR 1.1 | NCT01404312: 101/1,496 (6.8%) on Isoniazid |
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.
- Serpiginous choroiditis — n=24, PRR 1,283.7
- Vaginal flatulence — n=89, PRR 536.4
- Paradoxical drug reaction — n=554, PRR 231.7
- Immune reconstitution syndrome — n=116, PRR 126.7
- Choroiditis — n=33, PRR 125.3
- Disseminated bacillus calmette-guerin infection — n=36, PRR 108.5
- Congestive hepatopathy — n=26, PRR 80.8
- Immune reconstitution inflammatory syndrome — n=283, PRR 78.0
✓ A hand-written Bradford Hill causality assessment exists for this drug: Isoniazid ↔ Drug-induced liver injury.
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 Isoniazid?
In FDA FAERS, the most frequently co-reported reaction terms for Isoniazid are pyrexia, nausea, drug-induced liver injury, drug reaction with eosinophilia and systemic symptoms, vomiting, headache. 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 Isoniazid have an FDA boxed warning?
Yes. The current FDA label carries a boxed warning: Severe and sometimes fatal hepatitis associated with isoniazid therapy has been reported and may occur or may develop even after many months of treatment. The risk of developing hepatitis is age related. Approximate .
Do FAERS signals prove that Isoniazid 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 35400f1d-fd25-4bfa-a382-ac390e21bf2e, effective 20250708; matched on
openfda.generic_name.exact:"ISONIAZID") - 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, 1,128 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
ISONIAZID, 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.