Side Effects of Daraprim (pyrimethamine)

Daraprim (pyrimethamine) is an antiparasitic drug used to treat Toxoplasma gondii (toxoplasmosis) and plasmodia (malaria) infections.

Daraprim prevents parasites from producing important proteins by blocking the use of folic acid which is necessary for the production of proteins. Preventing parasites from producing important proteins prevents growth and development of new parasites. 

Common side effects of Daraprim include

• increased blood levels of phenylalanine,
• weight loss,
• vomiting,
• anemia,
• decreased white blood cell count,
• decreased platelets,
• tongue swelling, and
• blood in the urine.

Serious side effects of Daraprim include

• severe allergic reactions and
• abnormal heart rhythms.

Drug interactions of Daraprim include other drugs that block folic acid or drugs that suppress the bone marrow such as sulfonamides or trimethoprim-sulfamethoxazole combinations, proguanil, zidovudine, and methotrexate because it may increase the risk of bone marrow suppression.

There are no adequate studies of Daraprim in pregnant women. Daraprim should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Folic acid should also be given if it is used for the treatment of toxoplasmosis during pregnancy.

Daraprim is secreted in breast milk. Breastfeeding is not recommended while taking Daraprim.

Side effects of pyrimethamine include:

• Severe allergic reactions
• Increased blood levels of phenylalanine
• Weight loss
• Vomiting
• Anemia
• Reduced number of white blood cells
• Reduced number of platelets
• Swelling of the tongue
• Blood in the urine
• Abnormal heart rhythms

Hypersensitivity reactions, occasionally severe (such as Stevens-Johnson syndrome, toxic epidermal necrolysis, erythema multiforme, and anaphylaxis), and hyperphenylalaninemia, can occur particularly when pyrimethamine is administered concomitantly with a sulfonamide. Consult the complete prescribing information for the relevant sulfonamide for sulfonamideassociated adverse events.

With doses of pyrimethamine used for the treatment of toxoplasmosis, anorexia and vomiting may occur. Vomiting may be minimized by giving the medication with meals; it usually disappears promptly upon reduction of dosage.

Doses used in toxoplasmosis may produce

• megaloblastic anemia,
• leukopenia,
• thrombocytopenia,
• pancytopenia,
• neutropenia,
• atrophic glossitis,
• hematuria, and
• disorders of cardiac rhythm.

Hematologic effects, however, may also occur at low doses in certain individuals. Pulmonary eosinophilia has been reported rarely.

Pyrimethamine may be used with

• sulfonamides,
• quinine and other antimalarials, and with
• other antibiotics.

However, the concomitant use of other antifolic drugs or agents associated with myelosuppression including sulfonamides or trimethoprim-sulfamethoxazole combinations, proguanil, zidovudine, or cytostatic agents (e.g., methotrexate), while the patient is receiving pyrimethamine, may increase the risk of bone marrow suppression.

If signs of folate deficiency develop, pyrimethamine should be discontinued. Folinic acid (leucovorin) should be administered until normal hematopoiesis is restored.

Mild hepatotoxicity has been reported in some patients when lorazepam and pyrimethamine were administered concomitantly.