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Pyrimethamine
 

What is pyrimethamine?
 
 
Pyrimethamine (brand name: Daraprim®) is a systemic antiprotozoal medication used to treat parasitic infections including those caused by Hepatozoon americanum (a tick-borne parasite that causes canine hepatozoonosis) and Toxoplasma gondii (a parasite that causes the infection toxoplasmosis). 
 
Its use in cats, dogs and other species to treat certain parasitic infections is “off label” or “extra label”. Many drugs are commonly prescribed for off-label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions carefully, as they may be significantly different from those on the label.
 
How do I give my pet pyrimethamine?
  
It will take a few days before noting any effects, and the medication’s full effects may not be obvious for several weeks.
 
What if I miss giving my pet the medication?
 
If you miss a dose, give it as soon as you remember, and then continue with the regular dosing schedule. However, if it is almost time for the next dose, skip the missed dose and resume the regular dosing schedule. Do not give the pet two doses at once.
 
Are there any potential side effects?
 
Pyrimethamine may cause the following side effects:
  
In cats, side effects may be more severe.
 
This short-acting medication should stop working within 24 hours, although effects can be longer in pets with liver or kidney disease.
 
Are there any risk factors for this medication?
 
Pyrimethamine should NOT BE USED in: 
  
It should be USED WITH CAUTION in:
  
Are there any drug interactions I should be aware of?
 
Certain medications should be used cautiously with pyrimethamine, including: 
  
It is important to tell your veterinarian about any medications (including vitamins, supplements or herbal therapies) that your pet is taking before starting any treatment.
 
Is any monitoring needed with this medication?
  
How do I store pyrimethamine?
  
What should I do in case of emergency?
 
If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility.
 
  
 
 © Copyright 2025 LifeLearn Inc. Used and/or modified with permission under license. This content written by LifeLearn Animal Health (LifeLearn Inc.) is licensed to this practice for the personal use of our clients. Any copying, printing or further distribution is prohibited without the express written consent of LifeLearn. This content does not contain all available information for any referenced medications and has not been reviewed by the FDA Center for Veterinary Medicine, or Health Canada Veterinary Drugs Directorate. This content may help answer commonly asked questions, but is not a substitute for medical advice, or a proper consultation and/or clinical examination of your pet by a veterinarian. Please contact your veterinarian if you have any questions or concerns about your pet’s health. Last updated on Jul 3, 2024. 


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