PYRIMETHAMINE oral

Therapeutic action

– Antiprotozoal

Indications

– Treatment and secondary prophylaxis of toxoplasmosis in immunodeficient patients, in combination with sulfadiazine or clindamycin
– Primary prophylaxis of toxoplasmosis in immunodeficient patients, in combination with dapsone (only if co-trimoxazole cannot be used)
– Second-line treatment of isosporiasis in immunodeficient patients (only if co-trimoxazole cannot be used)

Forms and strengths

– 25 mg tablet

Dosage and duration

– Treatment of toxoplasmosis
Adult: 2 doses of 100 mg on D1, then 75 to 100 mg once daily for at least 6 weeks

– Secondary prophylaxis of toxoplasmosis
Adult: 25 to 50 mg once daily, as long as necessary

– Primary prophylaxis of toxoplasmosis
Adult: 50 to 75 mg once weekly, as long as necessary

– Treatment of isosporiasis
Adult: 50 to 75 mg once daily for 10 days

Contra-indications, adverse effects, precautions

– Do not administer to patients with severe renal or hepatic impairment.
– May cause: gastrointestinal disturbances, seizures, leucopenia, thrombocytopenia, megaloblastic anaemia due to folic acid deficiency.
– Administer calcium folinate to prevent folic acid deficiency.
– Avoid if possible combination with other folate antagonists: co-trimoxazole, methotrexate (increased risk of folic acid deficiency).
– Monitor combination with zidovudine (increased risk of zidovudine-associated haematotoxicity).
– Pregnancy: CONTRA-INDICATED during the first trimester
– Breast-feeding: no contra-indication; however avoid concomitant administration of other folate antagonists.

Remarks

– The combination of sulfadoxine/pyrimethmine is used for the treatment of uncomplicated falciparum malaria.
– Storage: below 25 °C