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Folate antagonist (antimalarial/antiprotozoal)

Pyrimethamine

Brand names: Daraprim

Adult dose

Dose: Toxoplasmosis: 50–75mg PO OD with sulfadiazine + folinic acid (specialist)

Route: PO

Frequency: OD

Clinical pearls

Toxoplasmosis (with sulfadiazine + folinic acid); cerebral toxoplasmosis in HIV
Always co-prescribe folinic acid 15mg/day to prevent cytopenias

Contraindications

Megaloblastic anaemia (folate deficiency)
Severe renal/hepatic impairment
Hypersensitivity

Side effects

Megaloblastic anaemia
Neutropenia
Thrombocytopenia
GI upset
Rash
SJS/TEN (with sulfonamide)

Interactions

Trimethoprim (additive folate antagonism)
Sulfonamides
Methotrexate
Phenytoin
Zidovudine

Monitoring

FBC weekly initially

Reference: BNF; BHIVA; https://bnf.nice.org.uk/drugs/pyrimethamine/. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

Pathways