Pyrimethamine is a dihydrofolate reductase inhibitor, it is absorbed from the GIT slowly but adequately. After oral administration pyrimethamine reaches peak plasma level in 4-6 hrs. It has a half life of about 4 days. It is concentrated in liver, spleen, kidney and lungs. Prophylactic concentration remains in blood for 2 weeks.

Pyrimethamine is a blood schizonticide, hence it can be used for prophylaxis. It can also be used for toxoplasmosis. Pyrimethamine is used in combination with other drugs.

Routes of Administration and Dosage

Pyrimethamine is commonly used in combination with a sulfonamide or a sulfone. Pyrimethamine 25 mg weekly in combination with another drug[sulfadoxine 500mgs]; acts as a causal prophylactic for falciparum and suppressive prophylactic for vivax malaria.

Contra Indications

Pyrimethamine is contraindicated in hypersensitivity, severe renal and hepatic impairment, in blood dyscrasias, infants less than 2 months, during pregnancy and lactation.

Precautions

High doses of pyrimethamine may make Anemia or other blood disorders worse. Patients with hepatic disease may have an increased chance of adverse effects. High doses of pyrimethamine may increase the chance of convulsions.

Interactions

Use of Flucytosine, Ganciclovir, Interferon, Mercaptopurine, Methotrexate, Plicamycin and zidovudine with Pyrimethamine can increase the toxicity of the drug.

Brand Names

FANSIDAR[pyrimethamine 25 mgs + sulfadoxine 500mgs]; METAKELFIN[pyrimethamine 25 mgs+sulfamethopyrazine 500 mgs]:

Pharmacokinetics | Indications | Routes of Administration and Dosage | Contra Indications | Precautions | Interactions | Brand Names

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