Drug · FAERS side-effect profile with label screen
Trimethoprim side effects: what 11,717 FDA adverse event reports show
Drug class
Dihydrofolate Reductase Inhibitor Antibacterial
FDA label (Established Pharmacologic Class)
Who reports
11,717 reports · 92% serious · 1,536 with death outcome · 69% female
openFDA FAERS counts, all years, deduplication not applied
Used for
To reduce the development of drug-resistant bacteria and maintain the effectiveness of trimethoprim tablets, USP and other antibacterial drugs, trimethoprim tablets, USP should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria.
FDA label, Indications and Usage
What it is
DESCRIPTION Trimethoprim is a synthetic antibacterial available in tablet form for oral administration. Each scored white tablet contains 100 mg trimethoprim. Trimethoprim is 5-[(3,4,5-trimethoxyphenyl)methyl]-2,4-pyrimidinediamine.
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) 1Likely indication confounding 2Reporting / coding artifact 3Lab value / disease marker 6Not in label — unassessed 28
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.
- 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. 1,069 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 |
|---|---|---|---|---|---|---|
| Cellulitis enterococcal | 16 | 3,529.5 1,510.8–8,245.4ROR 3,534.3 · χ² 17,655 / p <1e-300 | 487.6 EB05 318.2 · IC025 +4.2 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=16 | no trial arm names this drug |
| Pre-engraftment immune reaction | 41 | 1,904.1 1,225.1–2,959.3ROR 1,910.7 · χ² 36,601 / p <1e-300 | 640.6 EB05 492.3 · IC025 +5.7 3/3 methods agree | Not in label — unassessed | serious n=41 · 100% clinician | no trial arm names this drug |
| Synovial fluid analysis | 44 | 1,848.8 1,211.8–2,820.6ROR 1,855.7 · χ² 38,787 / p <1e-300 | 647.4 EB05 502.2 · IC025 +5.8 3/3 methods agree | Reporting / coding artifact | serious n=44 · ♀ 100% (drug 69%) · 100% clinician | no trial arm names this drug |
| Radiation inflammation | 17 | 476.2 278.8–813.4ROR 476.9 · χ² 5,979 / p <1e-300 | 264.0 EB05 174.6 · IC025 +4.2 3/3 methods agree | Not in label — unassessed | serious n=17 | no trial arm names this drug |
| Vaginal flatulence | 62 | 455.9 345.0–602.4ROR 458.3 · χ² 22,004 / p <1e-300 | 326.0 EB05 263.4 · IC025 +6.1 3/3 methods agree | Not in label — unassessed | serious n=62 · ♀ 100% (drug 69%) | no trial arm names this drug |
| Intestinal intraepithelial lymphocytes increased | 13 | 449.8 244.7–826.8ROR 450.3 · χ² 4,288 / p <1e-300 | 235.1 EB05 146.2 · IC025 +3.7 3/3 methods agree | Lab value / disease marker | serious n=13 | no trial arm names this drug |
| T-cell lymphoma recurrent | 11 | 388.2 202.2–745.5ROR 388.6 · χ² 3,172 / p <1e-300 | 205.4 EB05 122.4 · IC025 +3.4 3/3 methods agree | Not in label — unassessed | serious n=11 | no trial arm names this drug |
| Microvillous inclusion disease | 12 | 336.1 181.4–623.0ROR 336.5 · χ² 3,092 / p <1e-300 | 195.2 EB05 119.0 · IC025 +3.5 3/3 methods agree | Not in label — unassessed | serious n=12 | no trial arm names this drug |
| Probiotic therapy | 10 | 202.8 105.4–390.2ROR 203.0 · χ² 1,625 / p <1e-300 | 135.6 EB05 78.7 · IC025 +3.2 3/3 methods agree | Reporting / coding artifact | serious n=10 | no trial arm names this drug |
| Total lung capacity abnormal | 38 | 198.4 141.9–277.3ROR 199.0 · χ² 6,533 / p <1e-300 | 163.9 EB05 124.6 · IC025 +5.2 3/3 methods agree | Not in label — unassessed | serious n=38 · ♀ 0% (drug 69%) | no trial arm names this drug |
| Cryptitis | 13 | 183.5 103.7–324.8ROR 183.7 · χ² 1,975 / p <1e-300 | 134.1 EB05 83.4 · IC025 +3.6 3/3 methods agree | Not in label — unassessed | serious n=13 | no trial arm names this drug |
| Soft tissue disorder | 103 | 181.6 148.4–222.2ROR 183.2 · χ² 16,610 / p <1e-300 | 159.9 EB05 135.6 · IC025 +6.2 3/3 methods agree | Not in label — unassessed | serious n=103 · ♀ 100% (drug 69%) | no trial arm names this drug |
| Tenosynovitis stenosans | 49 | 171.9 128.3–230.4ROR 172.6 · χ² 7,432 / p <1e-300 | 147.8 EB05 116.2 · IC025 +5.5 3/3 methods agree | Not in label — unassessed | serious n=49 · ♀ 100% (drug 69%) · 100% clinician | no trial arm names this drug |
| Pulmonary vasculitis | 38 | 138.6 99.6–192.7ROR 139.0 · χ² 4,685 / p <1e-300 | 120.9 EB05 91.9 · IC025 +5.1 3/3 methods agree | Not in label — unassessed | serious n=38 · ♀ 0% (drug 69%) | no trial arm names this drug |
| Fear of eating | 19 | 118.5 74.5–188.5ROR 118.7 · χ² 1,965 / p <1e-300 | 100.2 EB05 67.8 · IC025 +4.1 3/3 methods agree | Not in label — unassessed | serious n=19 | no trial arm names this drug |
| Synovial disorder | 28 | 117.1 79.9–171.6ROR 117.4 · χ² 2,914 / p <1e-300 | 102.4 EB05 74.3 · IC025 +4.6 3/3 methods agree | Not in label — unassessed | serious n=28 · ♀ 100% (drug 69%) · 100% clinician | no trial arm names this drug |
| Capillaritis | 16 | 113.4 68.4–187.9ROR 113.6 · χ² 1,571 / p <1e-300 | 94.9 EB05 61.9 · IC025 +3.8 3/3 methods agree | Not in label — unassessed | serious n=16 | no trial arm names this drug |
| Anal inflammation | 36 | 107.5 76.8–150.4ROR 107.8 · χ² 3,481 / p <1e-300 | 96.3 EB05 72.7 · IC025 +4.9 3/3 methods agree | Not in label — unassessed | serious n=36 · ♀ 0% (drug 69%) · 100% clinician | no trial arm names this drug |
| Genital ulceration | 41 | 102.5 74.8–140.3ROR 102.8 · χ² 3,799 / p <1e-300 | 92.8 EB05 71.3 · IC025 +5.0 3/3 methods agree | Not in label — unassessed | serious n=41 | no trial arm names this drug |
| Red blood cell sedimentation rate decreased | 14 | 100.4 58.6–172.0ROR 100.6 · χ² 1,212 / p 9e-266 | 84.5 EB05 53.5 · IC025 +3.6 3/3 methods agree | Lab value / disease marker | serious n=14 | no trial arm names this drug |
| Swollen joint count | 13 | 99.7 57.1–174.4ROR 99.9 · χ² 1,111 / p 6e-244 | 83.3 EB05 51.8 · IC025 +3.5 3/3 methods agree | Not in label — unassessed | serious n=13 | no trial arm names this drug |
| Grip strength | 12 | 97.6 54.6–174.5ROR 97.7 · χ² 997 / p 3e-219 | 81.0 EB05 49.4 · IC025 +3.3 3/3 methods agree | Not in label — unassessed | serious n=12 | no trial arm names this drug |
| Deep vein thrombosis postoperative | 101 | 97.1 79.6–118.6ROR 98.0 · χ² 9,018 / p <1e-300 | 90.6 EB05 76.7 · IC025 +5.7 3/3 methods agree | Not in label — unassessed | serious n=101 · ♀ 100% (drug 69%) | no trial arm names this drug |
| Respiratory tract infection bacterial | 25 | 94.1 62.9–140.6ROR 94.3 · χ² 2,098 / p <1e-300 | 83.8 EB05 59.7 · IC025 +4.4 3/3 methods agree | Labeled (related wording) related wording | serious n=25 · ♀ 0% (drug 69%) · 100% clinician | no trial arm names this drug |
| Sars-cov-2 test negative | 32 | 87.8 61.6–125.2ROR 88.1 · χ² 2,535 / p <1e-300 | 79.9 EB05 59.2 · IC025 +4.6 3/3 methods agree | Reporting / coding artifact | serious n=32 · ♀ 0% (drug 69%) · 100% clinician | no trial arm names this drug |
| Soft tissue swelling | 24 | 79.9 53.1–120.3ROR 80.1 · χ² 1,714 / p <1e-300 | 72.3 EB05 51.1 · IC025 +4.2 3/3 methods agree | Not in label — unassessed | serious n=24 · ♀ 100% (drug 69%) | no trial arm names this drug |
| Encephalitis viral | 51 | 78.7 59.5–104.1ROR 79.0 · χ² 3,670 / p <1e-300 | 73.4 EB05 58.0 · IC025 +5.0 3/3 methods agree | Not in label — unassessed | serious n=51 · 100% clinician | no trial arm names this drug |
| Apoptosis | 13 | 77.8 44.6–135.5ROR 77.9 · χ² 871 / p 8e-192 | 67.5 EB05 42.0 · IC025 +3.4 3/3 methods agree | Not in label — unassessed | serious n=13 | no trial arm names this drug |
| Female genital tract fistula | 70 | 75.8 59.7–96.3ROR 76.3 · χ² 4,885 / p <1e-300 | 71.4 EB05 58.4 · IC025 +5.2 3/3 methods agree | Not in label — unassessed | serious n=70 · ♀ 100% (drug 69%) | no trial arm names this drug |
| Sars-cov-2 antibody test positive | 11 | 75.5 41.3–138.1ROR 75.6 · χ² 706 / p 8e-156 | 64.7 EB05 38.6 · IC025 +3.1 3/3 methods agree | Lab value / disease marker | serious n=11 | no trial arm names this drug |
| Facet joint syndrome | 122 | 72.0 60.1–86.2ROR 72.8 · χ² 8,141 / p <1e-300 | 68.5 EB05 58.9 · IC025 +5.5 3/3 methods agree | Not in label — unassessed | serious n=122 · ♀ 100% (drug 69%) · 91% clinician | no trial arm names this drug |
| Lupus vulgaris | 45 | 70.3 52.2–94.6ROR 70.5 · χ² 2,889 / p <1e-300 | 65.8 EB05 51.2 · IC025 +4.8 3/3 methods agree | Not in label — unassessed | serious n=45 · ♀ 100% (drug 69%) | no trial arm names this drug |
| Allergy to chemicals | 47 | 70.2 52.5–93.9ROR 70.5 · χ² 3,016 / p <1e-300 | 65.8 EB05 51.5 · IC025 +4.8 3/3 methods agree | Not in label — unassessed | serious n=47 · ♀ 100% (drug 69%) · 100% clinician | no trial arm names this drug |
| Spirometry abnormal | 21 | 66.3 42.9–102.5ROR 66.4 · χ² 1,239 / p 8e-272 | 60.6 EB05 41.8 · IC025 +4.0 3/3 methods agree | Lab value / disease marker | serious n=21 | no trial arm names this drug |
| Mite allergy | 21 | 60.9 39.4–94.0ROR 61.0 · χ² 1,138 / p 1e-249 | 56.0 EB05 38.7 · IC025 +3.9 3/3 methods agree | Not in label — unassessed | serious n=21 | no trial arm names this drug |
| Biliary sepsis | 15 | 60.0 35.9–100.4ROR 60.1 · χ² 786 / p 3e-173 | 54.3 EB05 34.9 · IC025 +3.5 3/3 methods agree | Not in label — unassessed | serious n=15 | no trial arm names this drug |
| Swollen joint count increased | 101 | 59.9 49.1–72.9ROR 60.4 · χ² 5,597 / p <1e-300 | 57.3 EB05 48.5 · IC025 +5.2 3/3 methods agree | Lab value / disease marker | serious n=101 · ♀ 100% (drug 69%) · 95% clinician | no trial arm names this drug |
| Scleritis | 49 | 56.6 42.6–75.2ROR 56.9 · χ² 2,541 / p <1e-300 | 53.8 EB05 42.3 · IC025 +4.7 3/3 methods agree | Not in label — unassessed | serious n=49 · ♀ 100% (drug 69%) · 100% clinician | no trial arm names this drug |
| C-reactive protein | 27 | 54.8 37.4–80.4ROR 55.0 · χ² 1,332 / p 6e-292 | 51.4 EB05 37.1 · IC025 +4.1 3/3 methods agree | Lab value / disease marker | serious n=27 · ♀ 100% (drug 69%) · 93% clinician | no trial arm names this drug |
| Pneumonia viral | 93 | 53.8 43.8–66.1ROR 54.2 · χ² 4,625 / p <1e-300 | 51.7 EB05 43.5 · IC025 +5.0 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=93 · ♀ 100% (drug 69%) | no trial arm names this drug |
Trial evidence (ClinicalTrials.gov)
ClinicalTrials.gov returned results-bearing trials mentioning Trimethoprim only as a background or rescue medication (NCT00729937, NCT00080119); 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 |
|---|---|---|---|---|---|---|
| Nausea | 968 | 2.2 2.1–2.3ROR 2.3 · χ² 654 / p 2e-144 | 2.2 EB05 2.1 · IC025 +1.0 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 2.5 | no trial arm names this drug |
| Off label use (used outside approved label) | 932 | 1.9 1.8–2.0ROR 2.0 · χ² 429 / p 1e-95 | 1.9 EB05 1.8 · IC025 +0.8 | Reporting / coding artifact | serious PRR 2.2 | no trial arm names this drug |
| Headache | 886 | 2.5 2.4–2.7ROR 2.7 · χ² 845 / p 4e-186 | 2.5 EB05 2.4 · IC025 +1.2 3/3 methods agree | Not in label — unassessed | serious PRR 3.2 | no trial arm names this drug |
| Diarrhoea (diarrhea) | 866 | 2.4 2.3–2.6ROR 2.5 · χ² 735 / p 3e-162 | 2.4 EB05 2.3 · IC025 +1.2 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 2.5 | no trial arm names this drug |
| Malaise (feeling unwell) | 862 | 3.5 3.3–3.7ROR 3.7 · χ² 1,578 / p <1e-300 | 3.5 EB05 3.3 · IC025 +1.7 3/3 methods agree | Not in label — unassessed | serious PRR 3.6 | no trial arm names this drug |
| Drug ineffective (drug did not work) | 783 | 1.1 1.0–1.1ROR 1.1 · χ² 3 / p 0.038 | 1.1 EB05 1.0 · IC025 -0.0 PRR-only: not supported by EBGM or IC | Reporting / coding artifact | serious PRR 1.8 | no trial arm names this drug |
| Dyspnoea (shortness of breath) | 752 | 2.4 2.2–2.6ROR 2.5 · χ² 617 / p 2e-136 | 2.4 EB05 2.2 · IC025 +1.1 3/3 methods agree | Not in label — unassessed | serious PRR 2.0 | no trial arm names this drug |
| Pyrexia (fever) | 741 | 3.8 3.6–4.1ROR 4.0 · χ² 1,573 / p <1e-300 | 3.8 EB05 3.6 · IC025 +1.8 3/3 methods agree | Labeled (related wording) related wording | serious PRR 3.0 | no trial arm names this drug |
| Vomiting | 740 | 2.8 2.6–3.0ROR 3.0 · χ² 891 / p 6e-196 | 2.8 EB05 2.7 · IC025 +1.4 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 2.5 | no trial arm names this drug |
| Fatigue (tiredness) | 674 | 1.6 1.4–1.7ROR 1.6 · χ² 137 / p 6e-32 | 1.6 EB05 1.5 · IC025 +0.5 | Not in label — unassessed | serious PRR 1.7 | no trial arm names this drug |
| Rash | 625 | 2.6 2.4–2.8ROR 2.7 · χ² 616 / p 3e-136 | 2.6 EB05 2.4 · IC025 +1.2 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 3.3 | no trial arm names this drug |
| Pain | 618 | 1.8 1.7–1.9ROR 1.8 · χ² 224 / p 5e-51 | 1.8 EB05 1.7 · IC025 +0.7 | Not in label — unassessed | serious PRR 1.7 | no trial arm names this drug |
| Dizziness | 615 | 2.2 2.0–2.4ROR 2.3 · χ² 417 / p 7e-93 | 2.2 EB05 2.1 · IC025 +1.0 3/3 methods agree | Not in label — unassessed | serious PRR 2.3 | no trial arm names this drug |
| Acute kidney injury (sudden kidney damage) | 607 | 7.2 6.6–7.7ROR 7.5 · χ² 3,219 / p <1e-300 | 7.1 EB05 6.6 · IC025 +2.7 3/3 methods agree | Not in label — unassessed | serious PRR 4.5 | no trial arm names this drug |
| Arthralgia (joint pain) | 563 | 2.4 2.2–2.6ROR 2.5 · χ² 483 / p 3e-107 | 2.4 EB05 2.3 · IC025 +1.1 3/3 methods agree | Not in label — unassessed | serious PRR 2.7 | 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.
- Pre-engraftment immune reaction — n=41, PRR 1,904.1
- Vaginal flatulence — n=62, PRR 455.9
- Total lung capacity abnormal — n=38, PRR 198.4
- Soft tissue disorder — n=103, PRR 181.6
- Tenosynovitis stenosans — n=49, PRR 171.9
- Pulmonary vasculitis — n=38, PRR 138.6
- Synovial disorder — n=28, PRR 117.1
- Anal inflammation — n=36, PRR 107.5
- Genital ulceration — n=41, PRR 102.5
- Deep vein thrombosis postoperative — n=101, PRR 97.1
✓ A hand-written Bradford Hill causality assessment exists for this drug: Trimethoprim (and co-trimoxazole) ↔ Hyperkalaemia.
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 Trimethoprim?
In FDA FAERS, the most frequently co-reported reaction terms for Trimethoprim are nausea, headache, diarrhoea, malaise, dyspnoea, pyrexia. 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 Trimethoprim have an FDA boxed warning?
No. The FDA label retrieved for Trimethoprim has no boxed warning; see the label's Warnings and Precautions for the recognised risks.
Do FAERS signals prove that Trimethoprim 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 73ccebc1-7412-2424-d62c-a5180ec52d81, effective 20240126; matched on
openfda.generic_name.exact:"TRIMETHOPRIM") - 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, 1,109 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
TRIMETHOPRIM, 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.