DHFR and toxoplasmosis: The most used drug combination to treat toxoplasmosis is pyrimethamine plus sulfadiazine, which inhibit Toxoplasma dihydrofolate reductase (DHFR) and dihydropteroate synthase, respectively, two enzymes involved in the synthesis of tetrahydrofolates, which are essential cofactors for DNA synthesis and methionine metabolism [37].