Pyrimethamine (By mouth)


Pyrimethamine (pir-i-METH-a-meen)

Helps prevent malaria and treats toxoplasmosis, an infection caused by a parasite. Is also used to prevent other kinds of infections.

Brand Name(s)


When This Medicine Should Not Be Used

How to Use This Medicine


  • Your doctor will tell you how much medicine to take and how often. You should not use more of this medicine than your doctor ordered.
  • You may take this medicine with food if it upsets your stomach or causes vomiting.
  • This medicine should be taken on a regular schedule. Try not to miss any doses. Keep taking the medicine for as long as your doctor has ordered, even if you feel better.

If a dose is missed:

  • Take the missed dose as soon as possible, unless it is almost time for your next dose.
  • Skip the missed dose if it is almost time for your next regular dose.
  • You should not use two doses at the same time.

How to Store and Dispose of This Medicine

  • Store the tablets in a tightly closed container away from heat, direct light, and moisture.
  • Keep all medicine out of the reach of children. Large doses of this medicine are especially harmful to children.

Drugs and Foods to Avoid

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

  • Make sure your doctor knows if you are taking phenytoin (Dilantin®), lorazepam (Ativan®), or sulfa drugs such as Bactrim® or Septra®.

Warnings While Using This Medicine

  • If you are pregnant or breastfeeding, talk to your doctor before taking this medicine. You may need to stop breastfeeding while taking this medicine.
  • Talk to your doctor before taking this medicine if you have seizures, any blood disorders, kidney disease, liver disease, or a history of alcoholism.
  • If you develop a skin rash, stop taking this medicine and call your doctor right away.
  • This medicine may help prevent malaria, but is not used to treat a severe attack of malaria.
  • Pyrimethamine may cause harmful side effects. To help treat these side effects, you may also be given another medicine called leucovorin. It is important that you take leucovorin exactly as your doctor ordered. Do not skip any doses.

Possible Side Effects While Using This Medicine

Call your doctor right away if you notice any of these side effects:

  • Skin rash, hives, or itching
  • Wheezing or trouble breathing
  • Swollen tongue
  • Unexplained fever, sore throat, or chills
  • Unusual bleeding, bruising, or purple spots on your skin
  • Yellowing of skin and eyes
  • Extreme tiredness
  • Pain when urinating or bloody urine

If you notice these less serious side effects, talk with your doctor:

  • Headache, dizziness
  • Nausea or upset stomach
  • Diarrhea

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088

Version Info

  • Last reviewed on 1/27/2017

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