What the label lists and what reports show
Trimethoprim side effects
Trimethoprim's FDA label lists its adverse reactions in its own words. FAERS holds 11,719 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is nausea (968 reports).
- Generic listed
Check it at the source: the trimethoprim FDA label on DailyMed (effective January 26, 2024, Dr. Reddy's Labratories Inc.); the FDA FAERS public dashboard.
What does the label list?
From the label: adverse reactionsThe adverse effects encountered most often with trimethoprim were rash and pruritus. To report SUSPECTED ADVERSE EVENTS, contact Dr. Reddy’s Laboratories Inc, at 1-888-375-3784 or FDA at 1-800-FDA-1088 or http://www.fda.gov/medwatch for voluntary reporting of adverse reactions. Dermatologic Rash, pruritus, and phototoxic skin eruptions. At the recommended dosage regimens of 100 mg b.i.d. or 200 mg q.d., each for 10 days, the incidence of rash is 2.9% to 6.7%. In clinical studies which employed high doses of trimethoprim, an elevated incidence of rash was noted. These rashes were maculopapular, morbilliform, pruritic, and generally mild to moderate, appearing 7 to 14 days after the initiation of therapy. Hypersensitivity Rare reports of exfoliative dermatitis, erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis (Lyell Syndrome), and anaphylaxis have been received. …
Source: FDA drug label, NDA018679 (Dr Reddys Labs Sa), as published by Dr. Reddy's Labratories Inc., effective January 26, 2024 (SPL set 73ccebc1-7412-2424-d62c-a5180ec52d81), via openFDA; the full label on DailyMed
What do FAERS reports show?
11,719 reports list trimethoprim among the medicines taken, each a report of something that happened, not proof the medicine caused it; 1,536 are coded as a death and 5,088 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 20 reactions below, 6 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Trimethoprim: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions