Pyrimethamine + Sulfadiazine: adverse event reports that FDA received
Combination of 2 active ingredients
The Green Book lists no brand name for exactly these active ingredients.
The openFDA records give the value "MSK" for the brand name and for the manufacturer name of each drug. FDA says that MSK means "masked". So the site cannot count a report for a brand.
Read this first. FDA says this about the data:
An API dataset query result cannot be used to estimate the risk associated with the product or compare one drug or device product with another. When looking at the results, be aware that there is no certainty that the reported drug or device caused the adverse event. This dataset should not be the sole source of information for clinical decision-making or other assumptions about the safety or effectiveness of a product. The adverse event may have been related to an underlying disease, other drugs used at the same time or other non-drug related sources.
FDA Center for Veterinary Medicine publishes these words. Source: Adverse Event Reports for Animal Drugs and Devices, read on . The data have the reports that FDA received through .
This page is not veterinary advice. For an animal that is ill, speak to a veterinarian.
Contacting a veterinarianHow to report to FDAFrom July 2013 to November 2024, FDA received 27 adverse event reports that name a drug with pyrimethamine and sulfadiazine as its active ingredients. Of the 27 reports, 22 (81.5%) are about horses.
In January to March 2026, FDA received no reports that name this drug. A report is not proof that a drug caused a sign.
Fewer than 20 reports named this drug in the 12 months before June 2026, so this page gives no change. Reports about horses are 81.5% of the reports that name this drug, and 1.4% of all reports.
Search engines list a drug page with 500 reports or more in all years. The page also needs 30 reports or more in the 12 months to June 2026. This page is under one of these numbers. The site keeps the page and keeps it out of search engines.
Since the last update of the FDA data
The latest update of the FDA data, recorded on , changed no count of this page.
January to March 2026 is the latest closed quarter in the data. In that quarter FDA received 0 reports that name pyrimethamine + sulfadiazine: 0 dog, 0 cat, 0 horse, 0 other or not given.
Signs that the reports list
A sign is a coded term from the report. The words in brackets are a plain gloss of the term. The percentage is the share of the 27 reports that list the sign. One report can list more than one sign.
The sign that is in the largest number of the reports comes first.
- Lethargy[unusually tired or inactive]14.8%4 reports
- Potency, Low14.8%4 reports
- Ataxia[unsteady, uncoordinated movement]11.1%3 reports
- Decreased appetite11.1%3 reports
- Diarrhoea[diarrhea]11.1%3 reports
- Leucopenia NOS[low white blood cell count]11.1%3 reports
- Product problem[a product quality report, not a sign in an animal]11.1%3 reports
- Death by euthanasia[the animal was euthanized]7.4%2 reports
- Decreased red blood cell count7.4%2 reports
- Lack of efficacy (protozoa) - NOS[the product did not have the expected effect: target not specified]7.4%2 reports
- Lack of efficacy - NOS[the product did not have the expected effect]7.4%2 reports
- Neurological signs NOS[NOS: not otherwise specified]7.4%2 reports
- Restlessness7.4%2 reports
- Abdominal discomfort3.7%1 reports
Show the next 16 signs
- Abnormal urine odour3.7%1 reports
- Agitation3.7%1 reports
- Anorexia[not eating]3.7%1 reports
- Biting -aggression3.7%1 reports
- Blistering3.7%1 reports
- Cold feeling of extremity3.7%1 reports
- Collapse NOS[NOS: not otherwise specified]3.7%1 reports
- Cutaneous oedema3.7%1 reports
- Death3.7%1 reports
- Decreased drinking3.7%1 reports
- Dehydration3.7%1 reports
- Discoloured urine3.7%1 reports
- Drooping eyelid3.7%1 reports
- Dysphagia3.7%1 reports
- Elevated liver enzymes[liver enzymes above the normal range]3.7%1 reports
- Gastric ulceration NOS[NOS: not otherwise specified]3.7%1 reports
The list shows 30 of 56 coded signs. A report is not proof that a drug caused a sign. Download all signs (CSV)
Reports by species
- Horse81.5%22
The share is of all 27 reports that name pyrimethamine + sulfadiazine. The other reports give a different species or no species.
Reports for each month, Jul 2021 to Jun 2026
No chart: no month has 5 or more reports.
No chart: no month has 5 or more reports.
No chart: no month has 5 or more reports.
No chart: no month has 5 or more reports.
The month is the month in which FDA received the report. Each chart has its own scale. FDA says that a report can take 3 to 6 months to reach the public data. The newest months can get more reports in a later update.
Reports by year
- Dog
- Cat
- Horse
- Other or not given
| Year | Dog | Cat | Horse | Other or not given | All species |
|---|---|---|---|---|---|
| 2024 | 0 | 0 | 0 | 1 | 1 |
| 2019 | 0 | 0 | 1 | 0 | 1 |
| 2018 | 0 | 0 | 4 | 0 | 4 |
| 2017 | 0 | 0 | 4 | 0 | 4 |
| 2016 | 0 | 0 | 4 | 1 | 5 |
| 2014 | 0 | 0 | 7 | 3 | 10 |
| 2013 | 0 | 0 | 2 | 0 | 2 |
2024 has the reports that FDA received through Nov 2024. Download the years (CSV)
What the reports record
Outcome at the time of the report
- Recovered/Normal25.9%7
- Recovered with Sequela[recovered, with a lasting effect]0%0
- Ongoing7.4%2
- Died3.7%1
- Euthanized7.4%2
- Outcome Unknown37%10
An outcome in a report is not proof that the drug caused it. The person who sends the report gives the outcome. Each share is of the 27 reports that name pyrimethamine + sulfadiazine.
A report about more than one animal can have more than one outcome.
Kind of report
- Safety issue66.7%18
- Lack of expected effectiveness3.7%1
- Both safety and lack of expected effectiveness3.7%1
- Manufacturing or product defect25.9%7
- Other0%0
22 reports say if the event was serious. 54.5% of them have the serious flag. The person who sends the report sets the flag.
Show age, weight, breed and route
Age of the animal
- Under 1 year0%0
- 1 to 3 years7.4%2
- 4 to 7 years3.7%1
- 8 to 11 years22.2%6
- 12 years and over44.4%12
- Age not given22.2%6
Weight of the animal
- Under 5 kg (11 lb)0%0
- 5 to 9.9 kg (11 to 22 lb)0%0
- 10 to 24.9 kg (22 to 55 lb)0%0
- 25 to 44.9 kg (55 to 99 lb)0%0
- 45 kg and over (99 lb and over)77.8%21
- Weight not given22.2%6
Breed, where the report gives one breed
- Quarter Horse22.2%6
- Thoroughbred14.8%4
- Standardbred7.4%2
- Missouri Fox Trotting Horse3.7%1
- Pura Raza Española (Andalusian)3.7%1
- Rocky Mountain Horse3.7%1
- Warmblood3.7%1
A breed with many animals has many reports.
Route in the report
- Oral70.4%19
Each bar is on a scale of 0 to 100%.
Approved animal drugs with these active ingredients (FDA Green Book)
This section is reference data. It has no report count.
The openFDA records give the value "MSK" for the brand name and for the manufacturer name of each drug. FDA says that MSK means "masked". So the site cannot count a report for a brand.
The Green Book lists no approved animal drug with these active ingredients. FDA also receives reports for human drugs and compounded drugs that veterinarians prescribe.
Other pages with one of these ingredients
A report names a drug by its set of active ingredients. Each set has its own page. The list is in order of name.
FDA pages for this drug
- How to Report Animal Drug and Device Side Effects and Product ProblemsThe FDA page that tells an owner or a veterinarian how to send a report.
- Animal Drugs @ FDAThe search page of the Green Book, the FDA list of approved animal drugs.
The site checked these addresses on . The links open in a new tab.
Cite this page
Pet Drug Reports. Pyrimethamine + Sulfadiazine: adverse event reports that FDA received. https://petdrugreports.com/drug/pyrimethamine-sulfadiazine/ Source: FDA Center for Veterinary Medicine, openFDA Animal and Veterinary adverse event reports, export of . Reports received through .
Where the data come from
The counts come from the openFDA Animal and Veterinary adverse event files, export of 30 Oct 2026. The files have the reports that the FDA Center for Veterinary Medicine received through 26 Jun 2026. The files mask brand and manufacturer names. The site counts a drug by the active ingredients that each record gives, and gives no count to a brand, an application or a company. Ingredient names and the lists of approved products follow the FDA Green Book of 2 Nov 2026. The site does not use the application number that a record has.
The site does not publish report text, lot numbers or details of a reporter. FDA's record is the authority. See how the site counts reports, the data sources and the corrections page.
Questions about these reports
- Which brand are these reports about?
The openFDA records give the value "MSK" for the brand name and for the manufacturer name of each drug. FDA says that MSK means "masked". So the site cannot count a report for a brand. The Green Book lists no brand name for exactly these active ingredients.
- Do the reports show that the drug caused the signs?
No. FDA states this about the data.
When looking at the results, be aware that there is no certainty that the reported drug or device caused the adverse event.
The adverse event may have been related to an underlying disease, other drugs used at the same time or other non-drug related sources.
FDA Center for Veterinary Medicine. Source: Adverse Event Reports for Animal Drugs and Devices
- How many reports did FDA receive in the latest 12 months?
FDA received no reports in the 12 months to June 2026. It received 1 report in the 12 months before. FDA says that a report can take 3 to 6 months to reach the public data. The newest months can get more reports in a later update.
- What kinds of report are in the count?
Of the 27 reports received from July 2013 to November 2024, 66.7% are about a safety issue only. 7.4% are about a lack of expected effectiveness, alone or with a safety issue. 25.9% are about a defect of the product or its package.