Cycloserine side effects: what 2,275 FDA adverse event reports show

Cycloserine · 92 reaction terms · 2,814 drug–reaction co-reports · data 2026-09-14

Drug class

Not stated in label

Who reports

2,275 reports · 97% serious · 442 with death outcome · 42% female

openFDA FAERS counts, all years, deduplication not applied

Used for

Cycloserine is indicated in the treatment of active pulmonary and extrapulmonary tuberculosis (including renal disease) when the causative organisms are susceptible to this drug and when treatment with the primary medications (streptomycin, isoniazid, rifampin, and ethambutol) has proved inadequate.

FDA label, Indications and Usage

What it is

DESCRIPTION D -Cycloserine, (R)-4-amino-3-isoxazolidinone, is a broad-spectrum antibiotic that is produced by a strain of Streptomyces orchidaceus and has also been synthesized. Cycloserine is a white to off-white powder that is soluble in water and stable in alkaline solution.

FDA label, Description section

Boxed warning

None in the current 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 (related wording) 2Likely indication confounding 1Reporting / coding artifact 4Outcome field, not a reaction 1Not in label — unassessed 32

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.
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.
Outcome field, not a reaction Death is a report outcome, not a reaction term. It is dominated by the underlying illness; see the seriousness profile and the boxed warning instead.
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. 52 further terms are in the interactive explorer. Reaction links open the term's cross-drug page.

Show: hide coding/lab/outcome terms hide indication terms unlabeled only hide PRR-only

Reaction	Reports	PRR 95% CI · ROR · χ²/p	EBGM EB05 · IC025	Label screen	Serious-only & strata	Trial cross-check
Electrocardiogram qt prolonged	291	75.1 67.4–83.7ROR 86.0 · χ² 21,072 / p <1e-300	74.2 EB05 67.3 · IC025 +5.9 3/3 methods agree	Not in label — unassessed	serious PRR 44.9 · 98% clinician	no trial data cached
Tuberculosis	96	69.3 56.9–84.4ROR 72.3 · χ² 6,351 / p <1e-300	67.9 EB05 57.3 · IC025 +5.3 3/3 methods agree	Likely indication confounding term in indications; also in warnings	serious PRR 40.9 · 92% clinician	no trial data cached
Hepatotoxicity (liver damage)	113	47.2 39.4–56.5ROR 49.6 · χ² 5,046 / p <1e-300	46.6 EB05 39.9 · IC025 +5.0 3/3 methods agree	Not in label — unassessed	serious PRR 28.5 · 97% clinician	no trial data cached
Drug resistance	120	43.3 36.3–51.5ROR 45.6 · χ² 4,895 / p <1e-300	42.8 EB05 36.7 · IC025 +4.9 3/3 methods agree	Reporting / coding artifact	serious PRR 28.6 · 100% clinician	no trial data cached
Drug reaction with eosinophilia and systemic symptoms	72	26.0 20.7–32.7ROR 26.9 · χ² 1,706 / p <1e-300	25.8 EB05 21.2 · IC025 +4.1 3/3 methods agree	Not in label — unassessed	serious PRR 15.5 · ♀ 83% (drug 42%) · 94% clinician	no trial data cached
Neuropathy peripheral (nerve damage in hands/feet)	235	23.0 20.3–25.9ROR 25.5 · χ² 4,925 / p <1e-300	22.9 EB05 20.5 · IC025 +4.2 3/3 methods agree	Not in label — unassessed	serious PRR 15.9 · 96% clinician	no trial data cached
Drug-induced liver injury	60	18.0 14.0–23.1ROR 18.4 · χ² 944 / p 2e-207	17.8 EB05 14.3 · IC025 +3.5 3/3 methods agree	Not in label — unassessed	serious PRR 10.8 · 93% clinician	no trial data cached
Polyneuropathy	23	17.9 11.9–26.8ROR 18.0 · χ² 349 / p 4e-78	17.5 EB05 12.1 · IC025 +3.0 3/3 methods agree	Not in label — unassessed	serious PRR 10.7 · ♀ 19% (drug 42%)	no trial data cached
Electrolyte imbalance	20	16.0 10.4–24.8ROR 16.2 · χ² 267 / p 2e-60	15.5 EB05 10.2 · IC025 +2.8 3/3 methods agree	Not in label — unassessed	serious PRR 9.9 · 100% clinician	no trial data cached
Psychotic disorder	44	13.7 10.3–18.4ROR 14.0 · χ² 507 / p 1e-112	13.5 EB05 10.3 · IC025 +3.1 3/3 methods agree	Not in label — unassessed	serious PRR 8.7 · 95% clinician	no trial data cached
Hypokalaemia (low potassium)	64	12.9 10.1–16.4ROR 13.2 · χ² 689 / p 3e-152	12.7 EB05 10.2 · IC025 +3.1 3/3 methods agree	Not in label — unassessed	serious PRR 7.8 · 90% clinician	no trial data cached
Myoclonus	16	12.4 7.6–20.2ROR 12.5 · χ² 156 / p 4e-36	11.3 EB05 6.8 · IC025 +2.4 3/3 methods agree	Not in label — unassessed	serious PRR 7.8	no trial data cached
Hypothyroidism	41	11.9 8.8–16.1ROR 12.1 · χ² 398 / p 8e-89	11.5 EB05 8.7 · IC025 +2.9 3/3 methods agree	Not in label — unassessed	serious PRR 7.6	no trial data cached
Nephropathy toxic	14	11.6 6.9–19.6ROR 11.7 · χ² 125 / p 2e-29	10.2 EB05 5.9 · IC025 +2.2 3/3 methods agree	Not in label — unassessed	serious PRR 7.1	no trial data cached
Anaemia (low red blood cells)	222	10.7 9.5–12.2ROR 11.8 · χ² 1,965 / p <1e-300	10.6 EB05 9.5 · IC025 +3.2 3/3 methods agree	Not in label — unassessed	serious PRR 6.8	no trial data cached
Neurotoxicity	20	10.6 6.9–16.4ROR 10.7 · χ² 165 / p 5e-38	9.6 EB05 6.2 · IC025 +2.4 3/3 methods agree	Not in label — unassessed	serious PRR 6.4 · 90% clinician	no trial data cached
Deafness	30	10.6 7.4–15.1ROR 10.7 · χ² 250 / p 1e-56	9.9 EB05 7.1 · IC025 +2.6 3/3 methods agree	Not in label — unassessed	serious PRR 6.5 · 97% clinician	no trial data cached
Hepatitis (liver inflammation)	29	10.5 7.3–15.0ROR 10.6 · χ² 239 / p 4e-54	9.8 EB05 6.9 · IC025 +2.6 3/3 methods agree	Not in label — unassessed	serious PRR 6.3 · 100% clinician	no trial data cached
Myelosuppression	37	10.0 7.3–13.8ROR 10.2 · χ² 292 / p 9e-66	9.5 EB05 7.0 · IC025 +2.6 3/3 methods agree	Not in label — unassessed	serious PRR 6.0 · 100% clinician	no trial data cached
Aspartate aminotransferase increased	55	9.6 7.4–12.4ROR 9.8 · χ² 413 / p 3e-92	9.2 EB05 7.2 · IC025 +2.7 3/3 methods agree	Labeled (related wording) related wording	serious PRR 6.4 · 91% clinician	no trial data cached
Sudden death	11	9.5 5.3–17.1ROR 9.5 · χ² 75 / p 2e-18	7.6 EB05 4.3 · IC025 +1.8 3/3 methods agree	Outcome field, not a reaction	serious PRR 5.6	no trial data cached
Hypomagnesaemia	14	9.3 5.5–15.7ROR 9.4 · χ² 96 / p 7e-23	7.8 EB05 4.7 · IC025 +2.0 3/3 methods agree	Not in label — unassessed	serious PRR 5.7	no trial data cached
Oral candidiasis (oral thrush)	13	9.2 5.4–15.9ROR 9.3 · χ² 87 / p 5e-21	7.6 EB05 4.5 · IC025 +1.9 3/3 methods agree	Not in label — unassessed	serious PRR 7.7	no trial data cached
Myocardial ischaemia	11	8.8 4.9–15.9ROR 8.9 · χ² 69 / p 5e-17	7.1 EB05 4.0 · IC025 +1.7 3/3 methods agree	Not in label — unassessed	serious PRR 5.3	no trial data cached
Hepatitis c	11	8.3 4.6–15.0ROR 8.3 · χ² 64 / p 8e-16	6.6 EB05 3.8 · IC025 +1.6 3/3 methods agree	Not in label — unassessed	serious PRR 5.3	no trial data cached
Haemoptysis	25	8.2 5.6–12.2ROR 8.3 · χ² 152 / p 3e-35	7.4 EB05 5.2 · IC025 +2.2 3/3 methods agree	Not in label — unassessed	serious PRR 5.3	no trial data cached
Incorrect product administration duration	18	8.2 5.2–13.0ROR 8.2 · χ² 106 / p 3e-25	7.1 EB05 4.6 · IC025 +2.0 3/3 methods agree	Reporting / coding artifact	serious n=18	no trial data cached
Arrhythmia	41	8.0 5.9–10.8ROR 8.1 · χ² 243 / p 5e-55	7.4 EB05 5.7 · IC025 +2.4 3/3 methods agree	Not in label — unassessed	serious PRR 4.9 · ♀ 18% (drug 42%) · 95% clinician	no trial data cached
Transaminases increased	19	7.9 5.0–12.3ROR 7.9 · χ² 108 / p 2e-25	6.9 EB05 4.6 · IC025 +2.0 3/3 methods agree	Not in label — unassessed	serious PRR 4.7	no trial data cached
Bone marrow failure	17	7.7 4.8–12.3ROR 7.7 · χ² 92 / p 4e-22	6.6 EB05 4.3 · IC025 +1.9 3/3 methods agree	Not in label — unassessed	serious PRR 4.6	no trial data cached
Intentional product use issue	70	7.3 5.8–9.2ROR 7.5 · χ² 378 / p 1e-84	7.1 EB05 5.8 · IC025 +2.4 3/3 methods agree	Reporting / coding artifact	serious PRR 6.4 · 100% clinician	no trial data cached
Hypocalcaemia (low calcium)	15	7.3 4.4–12.1ROR 7.4 · χ² 76 / p 2e-18	6.2 EB05 3.9 · IC025 +1.7 3/3 methods agree	Not in label — unassessed	serious PRR 4.6	no trial data cached
Altered state of consciousness	17	7.3 4.5–11.7ROR 7.3 · χ² 86 / p 1e-20	6.3 EB05 4.1 · IC025 +1.8 3/3 methods agree	Not in label — unassessed	serious PRR 4.4	no trial data cached
Tinnitus (ringing in the ears)	36	7.2 5.2–10.0ROR 7.3 · χ² 187 / p 8e-43	6.7 EB05 5.0 · IC025 +2.2 3/3 methods agree	Not in label — unassessed	serious PRR 6.6	no trial data cached
Lactic acidosis	25	7.2 4.9–10.6ROR 7.3 · χ² 127 / p 9e-30	6.5 EB05 4.6 · IC025 +2.0 3/3 methods agree	Not in label — unassessed	serious PRR 4.3 · 100% clinician	no trial data cached
Alanine aminotransferase increased	46	6.9 5.2–9.2ROR 7.0 · χ² 227 / p 1e-51	6.5 EB05 5.1 · IC025 +2.2 3/3 methods agree	Labeled (related wording) related wording	serious PRR 4.7	no trial data cached
Treatment failure	61	6.9 5.4–8.8ROR 7.0 · χ² 300 / p 2e-67	6.6 EB05 5.3 · IC025 +2.3 3/3 methods agree	Reporting / coding artifact	serious PRR 7.8 · 98% clinician	no trial data cached
Drug eruption	13	6.8 4.0–11.7ROR 6.8 · χ² 59 / p 9e-15	5.6 EB05 3.5 · IC025 +1.5 3/3 methods agree	Not in label — unassessed	serious PRR 4.7	no trial data cached
Hepatic function abnormal	27	6.7 4.6–9.8ROR 6.8 · χ² 126 / p 2e-29	6.1 EB05 4.4 · IC025 +2.0 3/3 methods agree	Not in label — unassessed	serious PRR 4.1	no trial data cached
Pancytopenia (all blood cells low)	40	6.6 4.9–9.0ROR 6.7 · χ² 186 / p 1e-42	6.2 EB05 4.7 · IC025 +2.1 3/3 methods agree	Not in label — unassessed	serious PRR 4.0 · 100% clinician	no trial data cached

Trial evidence (ClinicalTrials.gov)

Trial cross-check not yet run for this drug (ClinicalTrials.gov pull covers the 800 most-reported drugs first).

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
Electrocardiogram qt prolonged	291	75.1 67.4–83.7ROR 86.0 · χ² 21,072 / p <1e-300	74.2 EB05 67.3 · IC025 +5.9 3/3 methods agree	Not in label — unassessed	serious PRR 44.9 · 98% clinician	no trial data cached
Neuropathy peripheral (nerve damage in hands/feet)	235	23.0 20.3–25.9ROR 25.5 · χ² 4,925 / p <1e-300	22.9 EB05 20.5 · IC025 +4.2 3/3 methods agree	Not in label — unassessed	serious PRR 15.9 · 96% clinician	no trial data cached
Anaemia (low red blood cells)	222	10.7 9.5–12.2ROR 11.8 · χ² 1,965 / p <1e-300	10.6 EB05 9.5 · IC025 +3.2 3/3 methods agree	Not in label — unassessed	serious PRR 6.8	no trial data cached
Drug resistance	120	43.3 36.3–51.5ROR 45.6 · χ² 4,895 / p <1e-300	42.8 EB05 36.7 · IC025 +4.9 3/3 methods agree	Reporting / coding artifact	serious PRR 28.6 · 100% clinician	no trial data cached
Hepatotoxicity (liver damage)	113	47.2 39.4–56.5ROR 49.6 · χ² 5,046 / p <1e-300	46.6 EB05 39.9 · IC025 +5.0 3/3 methods agree	Not in label — unassessed	serious PRR 28.5 · 97% clinician	no trial data cached
Tuberculosis	96	69.3 56.9–84.4ROR 72.3 · χ² 6,351 / p <1e-300	67.9 EB05 57.3 · IC025 +5.3 3/3 methods agree	Likely indication confounding term in indications; also in warnings	serious PRR 40.9 · 92% clinician	no trial data cached
Drug reaction with eosinophilia and systemic symptoms	72	26.0 20.7–32.7ROR 26.9 · χ² 1,706 / p <1e-300	25.8 EB05 21.2 · IC025 +4.1 3/3 methods agree	Not in label — unassessed	serious PRR 15.5 · ♀ 83% (drug 42%) · 94% clinician	no trial data cached
Intentional product use issue	70	7.3 5.8–9.2ROR 7.5 · χ² 378 / p 1e-84	7.1 EB05 5.8 · IC025 +2.4 3/3 methods agree	Reporting / coding artifact	serious PRR 6.4 · 100% clinician	no trial data cached
Hypokalaemia (low potassium)	64	12.9 10.1–16.4ROR 13.2 · χ² 689 / p 3e-152	12.7 EB05 10.2 · IC025 +3.1 3/3 methods agree	Not in label — unassessed	serious PRR 7.8 · 90% clinician	no trial data cached
Gastrointestinal disorder	61	6.4 5.0–8.2ROR 6.5 · χ² 271 / p 3e-61	6.1 EB05 4.9 · IC025 +2.2 3/3 methods agree	Not in label — unassessed	serious PRR 5.7 · 97% clinician	no trial data cached
Treatment failure	61	6.9 5.4–8.8ROR 7.0 · χ² 300 / p 2e-67	6.6 EB05 5.3 · IC025 +2.3 3/3 methods agree	Reporting / coding artifact	serious PRR 7.8 · 98% clinician	no trial data cached
Drug-induced liver injury	60	18.0 14.0–23.1ROR 18.4 · χ² 944 / p 2e-207	17.8 EB05 14.3 · IC025 +3.5 3/3 methods agree	Not in label — unassessed	serious PRR 10.8 · 93% clinician	no trial data cached
Aspartate aminotransferase increased	55	9.6 7.4–12.4ROR 9.8 · χ² 413 / p 3e-92	9.2 EB05 7.2 · IC025 +2.7 3/3 methods agree	Labeled (related wording) related wording	serious PRR 6.4 · 91% clinician	no trial data cached
Thrombocytopenia (low platelets)	53	4.4 3.4–5.7ROR 4.5 · χ² 136 / p 1e-31	4.2 EB05 3.4 · IC025 +1.6 3/3 methods agree	Not in label — unassessed	serious PRR 2.6 · 98% clinician	no trial data cached
Respiratory failure	52	6.6 5.0–8.6ROR 6.7 · χ² 241 / p 1e-54	6.2 EB05 4.9 · IC025 +2.2 3/3 methods agree	Not in label — unassessed	serious PRR 3.9	no trial data cached

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.

Electrocardiogram qt prolonged — n=291, PRR 75.1
Hepatotoxicity — n=113, PRR 47.2
Drug reaction with eosinophilia and systemic symptoms — n=72, PRR 26.0
Neuropathy peripheral — n=235, PRR 23.0
Drug-induced liver injury — n=60, PRR 18.0
Polyneuropathy — n=23, PRR 17.9
Electrolyte imbalance — n=20, PRR 16.0
Psychotic disorder — n=44, PRR 13.7
Hypokalaemia — n=64, PRR 12.9
Hypothyroidism — n=41, PRR 11.9

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 Cycloserine?

In FDA FAERS, the most frequently co-reported reaction terms for Cycloserine are electrocardiogram qt prolonged, neuropathy peripheral, anaemia, hepatotoxicity, tuberculosis, drug reaction with eosinophilia and systemic symptoms. 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 Cycloserine have an FDA boxed warning?

No. The FDA label retrieved for Cycloserine has no boxed warning; see the label's Warnings and Precautions for the recognised risks.

Do FAERS signals prove that Cycloserine 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 8e7e2665-7a3d-3f54-9f92-5fe845f02ef9, effective 20240730; matched on openfda.generic_name.exact:"CYCLOSERINE")
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, field patient.drug.openfda.generic_name.exact, 92 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

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.