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Isoniazid Side Effects

The most commonly reported side effects of isoniazid include pyrexia, drug-induced liver injury, and off label use, based on 18,508 FDA adverse event reports from 2004 to 2025. 6.2% of reports found the drug to be ineffective.

Isoniazid side effects

Percentages show how often each reaction appears relative to total reports for isoniazid.

1
Drug Ineffective6.2%1,141
2
Pyrexia5.0%923
3
Drug-induced Liver Injury4.7%871
4
Off Label Use4.7%864
5
Drug Interaction4.6%848
6
Drug Reaction With Eosinophilia And Systemic Symptoms4.5%840
7
Nausea4.3%803
8
Vomiting3.1%566
9
Headache3.0%559
10
Paradoxical Drug Reaction2.8%517
11
Arthralgia2.7%506
12
Tuberculosis2.7%495
13
Condition Aggravated2.5%465
14
Rash2.5%461
15
Diarrhoea2.4%449

These are voluntary reports and do not establish that isoniazid caused these reactions.

Report severity

90.9%Serious16,815 reports
45.0%Hospitalizations8,325 reports
12.9%Fatal2,387 reports

Seriousness is determined by the reporter, not by OpenClaim.

Isoniazid drug interactions

Other drugs that appear in adverse event reports alongside isoniazid. Drugs flagged as a suspected cause appear in the first column. Drugs taken at the same time but not suspected appear in the second.

Also suspected

1
Pyrazinamide28.4%5,264
2
Ethambutol-hydrochloride25.9%4,785
3
Rifampin20.5%3,801
4
Adalimumab6.5%1,194
5
Levofloxacin6.1%1,137
6
Moxifloxacin-hydrochloride4.9%899
7
Linezolid4.5%824
8
Etanercept4.3%796
9
Infliximab4.1%768
10
Lamivudine3.9%728
11
Tenofovir3.9%724
12
Methotrexate3.9%716
13
Efavirenz3.6%669
14
Prednisone3.6%662
15
Prednisolone2.8%524

Taken alongside

1
Ethambutol-hydrochloride16.3%3,025
2
Pyrazinamide14.1%2,601
3
Pyridoxine8.9%1,639
4
Rifampin8.3%1,535
5
Prednisone6.7%1,245
6
Methotrexate5.3%974
7
Folic-acid4.8%889
8
Acetaminophen4.5%831
9
Omeprazole4.4%813
10
Prednisolone4.3%790
11
Sulfamethoxazole3.6%663
12
Aspirin3.3%603
13
Levofloxacin3.1%582
14
Amlodipine2.8%520
15
Trimethoprim2.8%515

Co-occurrence in adverse event reports does not establish a drug interaction. Patients often take multiple medications, and these lists reflect prescribing patterns rather than causal relationships. Consult a healthcare provider about potential drug interactions.

Who reports isoniazid side effects

44.4% of isoniazid adverse event reports involve female patients and 44.5% involve male patients. The largest age group is adult at 67%. These figures reflect who reports side effects, not underlying risk.

Sex

Female44.4%
Male44.5%
Unknown11.1%

Age group

< 22.4%
2–114.0%
12–173.5%
18–6467.3%
65+22.7%

What is isoniazid used for

Conditions and purposes for which patients were taking isoniazid when the adverse event was reported.

Abdominal Wall WoundAbscessAccidental Drug Intake By ChildAccidental Exposure To ProductAcid Fast Bacilli InfectionAcute Kidney InjuryAdrenal Gland TuberculosisAdverse EventAdverse ReactionAlopecia AreataAnal FistulaAnkylosing SpondylitisAnti-infective TherapyAnti-interferon Antibody PositiveAntibiotic Prophylaxis

Showing 15 of 496 indications

Isoniazid brand names and reporting trend

Isoniazid is sold under the brand name Dow-isoniazid.

Brand names

Dow-isoniazid18,669

Quarterly reports (20042025)

20052010201520202025

An upward trend reflects increased FAERS reporting overall, not necessarily increased risk.

Taking isoniazid with another medication?

Ask OpenClaim about your specific drug combination. Get a sourced report using FDA data, drug labels, and medical literature.