Pyrimethamine

• Antimicrobial that inhibits the reduction of dihydrofolic to tetrahydrofolic acid
• Indications include toxoplasmosis and malaria
• Major adverse effects is bone marrow suppression, so need to monitor CBC
  • Pancytopenia, which is reversible with leucovorin
  • GI intolerance
  • Other: rash, hepatitis, headache, dizziness, insomnia
• Monitoring
  • CBC q2d initially, then decreasing frequency