Pyrimethamine

Pyrimethamine is a prescription medication used to malaria or toxoplasmosis, a disease caused by parasites. It is also used to prevent malaria. Pyrimethamine belongs to a group of drugs called diaminopyrimidines. These help to fight against parasites.

This medication is comes in tablet form and is taken up to 2 times a day, with or without food. 

Common side effects of pyrimethamine include anorexia, vomiting, or anemia. 

Pyrimethamine is a prescription medication used to prevent and treat malaria. It is also used to treat toxoplasmosis, a disease caused by parasites.

This medication may be prescribed for other uses. Ask your doctor or pharmacist for more information. 

Pyrimethamine may be found in some form under the following brand names:

• Daraprim

• Fansidar

• Rebalance

Serious side effects have been reported with pyrimethamine. See the “Pyrimethamine Precautions” section.

Common side effects of pyrimethamine include the following:

• anorexia
• vomiting
• decreases in blood cell counts

​This is not a complete list of pyrimethamine side effects. Ask your doctor or pharmacist for more information.

Tell your doctor if you have any side effect that bothers you or that does not go away.

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

Tell your doctor about all the medicines you take, including prescription and non-prescription medicines, vitamins, and herbal supplements. Especially tell your doctor if you take:

• phenytoin (Dilantin)
• antifolic drugs such as
  • sulfonamides
  • trimethoprim-sulfamethoxazole
  • proguanil
  • zidovudine
  • cytostatic agents such as methotrexate
• lorazepam (Ativan)

This is not a complete list of pyrimethamine drug interactions. Ask your doctor or pharmacist for more information.

Serious side effects have been reported with pyrimethamine including the following: 

• Rash. At the first appearance of a skin rash, stop use of pyrimethamine and seek medical attention immediately.
• Folate deficiency. If you have folate deficiency, your doctor may reduce the dose or stop the medication. Your doctor may prescribe Folinic acid (leucovorin). 
• Cancer. There have been 2 cases in humans where pyrimethamine was taken for long period of time and resulted in cancer. 
• Accidental Ingestion. Keep pyrimethamine out of the reach of children and infants. Deaths in pediatric patients have been reported after accidental ingestion.
• Hypersensitivity reactions, occasionally severe (such as Stevens-Johnson syndrome, toxic epidermal necrolysis, erythema multiforme, and anaphylaxis). At the first appearance of a skin rash, stop use of pyrimethamine and seek medical attention immediately. If you experience a sore throat, pallor, purpura, or glossitis, seek medical attention immediately. These may be early indications of serious disorders. Your doctor will probably need to stop treatment with pyrimethamine. 

Do not take pyrimethamine if you:

• are allergic to pyrimethamine or to any of its ingredients
• have megaloblastic anemia due to folate deficiency

Medications can interact with certain foods. In some cases, this may be harmful and your doctor may advise you to avoid certain foods. In the case of pyrimethamine, there are no specific foods that you must exclude from your diet when receiving this medication.

Before taking pyrimethamine, tell your doctor about all of your medical conditions. Especially tell your doctor if you:

• are allergic to pyrimethamine or to any of its ingredients
• have folate deficiency
• have or have a history of seizures
• have kidney or liver problems
• have malabsorption syndrome
• take phenytoin
• have alcoholism
• are pregnant or plan to become pregnant
• are breastfeeding or plan to breastfeed

Tell your doctor about all the medicines you take including prescription and non-prescription medicines, vitamins, and herbal supplements.

Tell your doctor if you are pregnant or plan to become pregnant.

The FDA categorizes medications based on safety for use during pregnancy. Five categories - A, B, C, D, and X, are used to classify the possible risks to an unborn baby when a medication is taken during pregnancy.

Pyrimethamine falls into category C. In animal studies, pregnant animals were given this medication and had some babies born with problems. No well-controlled studies have been done in humans. Therefore, this medication may be used if the potential benefits to the mother outweigh the potential risks to the unborn child.

Taking folinic acid is strongly recommended when used for the treatment of toxoplasmosis during pregnancy.

Tell your doctor if you are breastfeeding or plan to breastfeed.

Pyrimethamine has been detected in human breast milk. Because of the possibility for adverse reactions in nursing infants from pyrimethamine, a choice should be made whether to stop nursing or to stop use of this medication. The importance of the drug to the mother should be considered.

Take pyrimethamine exactly as prescribed.

Take this medication exactly as prescribed by your doctor. Follow the directions on your prescription label carefully.

The dose your doctor recommends may be based on the following:

• the condition being treated
• other medical conditions you have
• other medications you are taking
• how you respond to this medication
• your weight
• your age

The recommended starting dose range of Daraprim (pyrimethamine) for the treatment of toxoplasmosis in adults is 50 to 75 mg daily. Daraprim is given with 1 to 4 g daily of a sulfonamide. After a few weeks, the doctor may reduce the dose.

The recommended dosage of Daraprim (pyrimethamine) for the treatment of toxoplasmosis in children is 1 mg/kg/day divided into 2 equal daily doses. After a few days, the doctor may reduce the dose. 

• If Daraprim is given alone for the treatment of acute malaria, the recommended dose in adults is 50 mg for 2 days. In children 4 through 10 years old, Daraprim may be given at 25 mg daily for 2 days. 

• Adults and pediatric patients over 10 years – 25 mg (1 tablet) once weekly
• Children 4 through 10 years – 12.5 mg (1/2 tablet) once weekly
• Infants and children under 4 years – 6.25 mg (1/4 tablet) once weekly

If you take too much pyrimethamine, call your healthcare provider or local Poison Control Center, or seek emergency medical attention right away.

• Store at 15° to 25°C (59° to 77°F) in a dry place and protect from light.
• Keep this and all medicines out of the reach of children.