What is the correct combination for treating toxoplasmosis with Sulfadiazine?

The correct combination for treating toxoplasmosis with Sulfadiazine is Pyrimethamine. This pairing is critical in the management of the infection due to Toxoplasma gondii, particularly in immunocompromised patients, such as those with HIV/AIDS.

Sulfadiazine acts as a sulfa antibiotic that inhibits bacterial folic acid synthesis by competing with para-aminobenzoic acid (PABA). Pyrimethamine, on the other hand, is a dihydrofolate reductase inhibitor that effectively blocks the folate synthesis pathway as it inhibits the conversion of dihydrofolate to tetrahydrofolate, an essential step for nucleic acid synthesis and cell replication. When used together, they provide a synergistic effect, enhancing the overall efficacy of the treatment for toxoplasmosis.

This combination is the standard of care for toxoplasmosis due to the ability of both drugs to target separate but complementary pathways in the folate synthesis process, ultimately leading to a more effective treatment compared to either drug used alone.