Active ingredient · pooled across combinations
Trimethoprim: adverse event reports, pooled
3 ingredient sets in reports · 12 FDA-approved applications in the Green Book
Trimethoprim appears, alone or combined with other ingredients, in 460 reports in FDA's animal adverse event database (March 1987 to March 2026). The figures here pool all 3 ingredient sets that include it.
The Green Book lists 12 FDA-approved applications containing it. openFDA masks brand and manufacturer names in adverse event records, so the reports counted here cannot be attributed to a particular brand.
24 reports arrived in the 12 months to March 2026, up 167% from 9 in the 12 months before. FDA posts reports quarterly with a delay of three to six months, so the newest months are incomplete and usually grow in later releases. That is about 12 reports a year over its reporting history and 0% of all reports.
Pooled across every set, the terms listed most often are death (15.9%), lethargy (9.8%) and vomiting (9.8%). Many drugs combine several ingredients, and many reports list several drugs, so a term on this page may relate to any of them or to none.
Of reports that state seriousness, 55.3% were classed as serious (38.6% across the whole database); 23% record a death or euthanasia (6.4% overall). Ingredients used in older or sicker animals, or in anaesthesia and cancer care, carry higher shares for that reason alone.
Ingredient sets that include trimethoprim
| Active ingredients recorded for the drug | Reports | Share of this page's reports | Latest 12 months |
|---|---|---|---|
| Sulfadiazine + Trimethoprim | 286 | 62.2% | 6 |
| Trimethoprim | 173 | 37.6% | 18 |
| Sulfadimethoxine + Trimethoprim | 2 | 0.4% | 0 |
Ordered by report count. FDA states that these data "cannot be used to estimate the risk associated with the product or compare one drug or device product with another"; counts follow sales volume and years on the market. A report can list more than one set, so shares can add to more than 100%.
Signs listed in reports, pooled
share of trimethoprim reports listing the termall reports in the database
- Death15.9%73
- Lethargy[unusually tired or inactive]9.8%45
- Vomiting9.8%45
- Anorexia[not eating]8.9%41
- Diarrhoea[diarrhea]8.5%39
- Depression[dull, quiet or withdrawn]8%37
- Fever7.2%33
- Death by euthanasia[the animal was euthanized]6.7%31
- Thrombocytopenia[low platelet count]6.1%28
- Anaemia NOS[low red blood cell count]5.9%27
- Elevated alanine aminotransferase (ALT)[a liver enzyme above the normal range]5.7%26
- Collapse5.2%24
- Other abnormal test result NOS[abnormal laboratory result, type not specified]5.2%24
- Decreased appetite3.9%18
- Anaphylaxis[sudden severe allergic-type reaction]3.7%17
- Elevated serum alkaline phosphatase (SAP)[a liver and bone enzyme above the normal range]3.7%17
- Lack of efficacy - NOS[the product did not have the expected effect]3.7%17
- Weight loss3.7%17
- Convulsion[seizure]3.5%16
- Elevated blood urea nitrogen (BUN)[a kidney value above the normal range]3.5%16
- Pruritus[itching]3.5%16
- Leucocytosis NOS[high white blood cell count]3.3%15
- Elevated creatinine[a kidney value above the normal range]3%14
- Lameness3%14
- Cough2.8%13
- Skin lesion NOS[NOS: not otherwise specified]2.8%13
- Ataxia[unsteady, uncoordinated movement]2.6%12
- Behavioural disorder NOS[behaviour change, type not specified]2.6%12
- Emesis[vomiting]2.6%12
- Not eating2.6%12
Pooled across every ingredient set and every report that names the ingredient. One report can list several terms and several drugs; a term here may relate to any of them or to none.
Monthly reports by species, five years
By month of receipt; each panel has its own scale. The newest months are incomplete because FDA posts reports with a delay of three to six months.
Outcomes, report types and ages
Outcome recorded in the report
What kind of report it was
Age of the animal
Coloured bar: reports naming trimethoprim. Grey bar: all 1,357,245 reports. Outcomes are as stated by the reporter; FDA has not necessarily determined whether any product played a part.
In context
| Measure | Trimethoprim | All reports |
|---|---|---|
| Reports | 460 | 1,357,245 |
| Latest 12 months against the 12 before | +167% | -5% |
| Classed serious, of reports stating it | 55.3% | 38.6% |
| Death or euthanasia recorded, per 1,000 reports | 230.4 | 63.8 |
| Filed as lack of expected effectiveness (wholly or partly) | 6.3% | 23% |
Shares of reports, not of animals treated: how many animals receive the ingredient is not public. Ingredients used in anaesthesia, cancer care or in old animals carry more serious outcomes in their reports for that reason alone.
FDA-approved products containing trimethoprim (Green Book)
Reference information, not report statistics. openFDA masks brand and manufacturer names in adverse event records, so the reports counted here cannot be attributed to a particular brand. The list below is the FDA Green Book as of 1 Oct 2026; nothing on this page says which of these products, if any, a report concerned.
| Trade name | Active ingredients | Sponsor | Approved for | Application |
|---|---|---|---|---|
| Tribrissen 120 Tablets; Tribrissen 30 Tablets; Tribrissen 480 Tablets; Tribrissen 960 Tablets | Sulfadiazine, Trimethoprim | Intervet, Inc. | Dogs | NADA 095-614 |
| Tribrissen 24% Injection | Sulfadiazine Sodium, Trimethoprim | Intervet, Inc. | Dogs | NADA 105-093 |
| Tribrissen 48% Injection | Sulfadiazine, Trimethoprim | Intervet, Inc. | Horses | NADA 106-965 |
| Di-Trim Tablets | Sulfadiazine, Trimethoprim | Zoetis Inc. | Dogs | NADA 115-578 |
| Tribrissen 400 Oral Paste | Sulfadiazine, Trimethoprim | Intervet, Inc. | Horses | NADA 131-918 |
| Di-Trim 24% | Sulfadiazine, Trimethoprim | Zoetis Inc. | Dogs | NADA 132-486 |
| Di-Trim 48% Injection | Sulfadiazine, Trimethoprim | Zoetis Inc. | Horses | NADA 134-778 |
| Di-Trim 400 Paste | Sulfadiazine, Trimethoprim | Zoetis Inc. | Horses | NADA 136-342 |
| Tribrissen 60 Oral Suspension | Sulfadiazine, Trimethoprim | Intervet, Inc. | Dogs | NADA 136-741 |
| EQUISUL-SDT | Sulfadiazine, Trimethoprim | Aurora Pharmaceutical, Inc. | Horses | NADA 141-360 |
| Uniprim Powder | Sulfadiazine, Trimethoprim | Neogen Corp. | Horses | ANADA 200-033 |
| Tucoprim Powder | Sulfadiazine, Trimethoprim | Zoetis Inc. | Horses | ANADA 200-244 |
Species are the major species the Green Book search lists for the application ("—" where it lists another species or none). Approval dates are not part of the Green Book listing files and are not shown. Pioneer applications (NADA) come first, then generics (ANADA).
Questions about trimethoprim reports
How many FDA adverse event reports mention trimethoprim?
460 reports through March 2026, 24 of them in the latest 12 months, counting trimethoprim alone and in combinations.
Which brands do these reports concern?
That cannot be known from the public data. openFDA masks brand and manufacturer names in adverse event records, so the reports counted here cannot be attributed to a particular brand. The Green Book reference list on this page names approved products containing trimethoprim without any counts.
In which combinations is trimethoprim reported?
Sulfadiazine + Trimethoprim (62.2% of these reports), Trimethoprim (37.6% of these reports) and Sulfadimethoxine + Trimethoprim (0.4% of these reports).
What reactions are reported for trimethoprim?
death (15.9%), lethargy (9.8%), vomiting (9.8%), anorexia (8.9%) and diarrhoea (8.5%). Shares are of reports naming the ingredient; one report can list several terms.
Which animals are these reports about?
dog (53.3%), horse (24.1%) and cat (3.9%).
Does a high count mean trimethoprim is a problem ingredient?
A count cannot show that. FDA states that "there is no certainty that the reported drug or device caused the adverse event" and that the event "may have been related to an underlying disease, other drugs used at the same time or other non-drug related sources." Widely used ingredients collect more reports because more animals receive them.
How do I report a problem?
Call the drug company using the number on the label, or send Form FDA 1932a to FDA. See the guide on how to report.
Where this comes from. Counts are built from the openFDA Animal & Veterinary adverse event bulk files released 28 Sep 2026, which hold reports FDA's Center for Veterinary Medicine received through 31 Mar 2026. openFDA masks brand and manufacturer names in these files, so drugs are counted by the active ingredients each record discloses and no figure is attributed to a brand, application or company. Ingredient names, and the separate reference lists of approved products, follow the FDA Green Book as of 1 Oct 2026. Ingredient names follow the Green Book; salts and forms are kept as FDA lists them. Drug entries are matched by the active ingredients their unmasked ingredient field discloses. No report text, lot numbers or reporter details are published. See the methodology and sources; FDA's record is authoritative, and corrections are handled within five working days.