pyrimethamine ChEMBL:CHEMBL36 ARO:3009163 PubChem:4993 antibiotic_resistance CAS:58-14-0 ChEBI:8673 Pyrimethamine is a competitive inhibitor of dihydrofolate reductase (DHFR). DHFR is a key enzyme in the redox cycle for production of tetrahydrofolate, a cofactor that is required for the synthesis of DNA and proteins. It is typically used in combination with other drugs to treat parasitic infections, including malaria and toxoplasmosis. When combined with sulfadoxine, it can be used as prophylaxis for Pneumocystis jerovecii (fungi) induced pneumonia (PCP). However, this compound is generally not recommended for PCP prophylaxis unless trimethoprim-sulfamethoxazole, pentamidine, dapsone/pyrimethamine/leucovorin, atovaquone or dapsone cannot be used. antifungal without defined classification