Pyrimethamine

Note: As of 2015, pyrimethamine is only available in the US through a special pharmacy program

Administration

• Type: Antiparasitic, indicated for treatment and prophylaxis of Toxoplasmosis and malaria
• Dosage Forms:
• Routes of Administration: Oral
• Common Trade Names:

Adult Dosing

Indications by Disease

Disease	Dose	Context
Toxoplasmosis	200mg PO load then 50mg PO q24hrs x 4 weeks	Immunocompetent with Leucovorin and Sulfadiazine
Toxoplasmosis	200mg PO load then 75mg PO q24hrs x 4-8 weeks	Immunosuppressed

Pediatric Dosing

Indications by Disease

Disease	Dose	Context
Toxoplasmosis	2mg/kg/day PO x 2 days then 1mg/kg/day x 2-6 months, then 1mg/kg MWF	Congenital/Pediatric

Special Populations

• Pregnancy Rating: C
• Lactation risk: Infant risk minimal
• Renal dosing:

Contraindications

• Allergy to class/drug
• megaloblastic anemia due to folate deficiency

Adverse Reactions

Serious

• SJS, TEN
• Pancytopenia, leukopenia, thrombocytopenia, megaloblastic anemia

Common

• Rash

Pharmacology

• Half-life: 52-97 hours
• Metabolism: Hepatic
• Excretion:

Mechanism of Action

• Blocks protozoal dihydrofolate reductase, inhibiting nucleic acid synthesis