Trimethoprim + Sulfamethoxazole
17 adverse event reports submitted to the FDA
Active Ingredients
Administration Routes
Species Affected
Most Affected Breeds
Most Reported Reactions
Outcome Breakdown
Data Summary
| Metric | Value |
|---|---|
| Total adverse event reports | 17 |
| Reports involving death | 4 |
| Case-fatality rate (reported events) | 2350.0% |
| Distinct species in reports | 1 |
| Distinct breeds in reports | 14 |
| Distinct reactions reported | 20 |
| Active ingredients on file | 1 |
Source: FDA Center for Veterinary Medicine — Adverse Event Reporting (CVM AER). Counts reflect voluntary reports only.
Trimethoprim + Sulfamethoxazole Adverse Event Insights
The FDA Center for Veterinary Medicine database currently holds 17 adverse event reports referencing Trimethoprim + Sulfamethoxazole, including 4 reports in which the animal died — a 2350.0% case-fatality figure among reported events only, not a population-level mortality rate. Active ingredient on file: Trimethoprim + Sulfamethoxazole. Reported administration routes include Oral, Unknown. These numbers reflect voluntary submissions from pet owners, veterinarians, and manufacturers and therefore under-represent mild events and over-represent severe ones — a pattern the FDA has documented repeatedly for pharmacovigilance datasets.
The species most frequently named in Trimethoprim + Sulfamethoxazole reports are Dog (17 reports), with Dog accounting for the largest share. Within those species, Retriever - Labrador (3), Bulldog (2), Crossbred Canine/dog (1) appear most often — though breed popularity and ownership density shape these counts as much as any drug-specific sensitivity. This distribution matters because the same active ingredient can behave very differently across body sizes, ages, and species physiology.
The most commonly reported clinical signs associated with Trimethoprim + Sulfamethoxazole are Lethargy (see also Central nervous system depression in 'Neurological') (5), Vomiting (5), Seizure NOS (4), Other abnormal test result NOS (3). Of the 17 reports with a coded outcome, Ongoing is the leading category at 29.4%. Because FDA adverse event data describes correlation rather than causation, these figures are best used to frame informed questions with a veterinarian and to compare reporting patterns across related products — not as a standalone safety verdict on Trimethoprim + Sulfamethoxazole.
Source: FDA Center for Veterinary Medicine — Adverse Event Reports FDA Center for Veterinary Medicine — Adverse Event Reports Data reflects voluntary submissions and may not represent actual incidence rates
Read our methodology — how this data is sourced, computed, and verified.