An infant receiving pyrimethamine and sulfadiazine for congenital toxoplasmosis develops a falling total leukocyte count with absolute neutrophil count of 400/mm3. Which intervention directly addresses this adverse effect?

• A Add folinic acid rescue and monitor weekly blood counts ✓
• B Stop sulfadiazine and substitute clindamycin permanently
• C Reduce the pyrimethamine dose by half without adding any supplement
• D Administer vitamin K to correct the cytopenia

Explanation

Pyrimethamine is a dihydrofolate reductase inhibitor that causes reversible bone marrow suppression, most importantly neutropenia and thrombocytopenia. Folinic acid is given alongside throughout the year of therapy specifically to protect the marrow while preserving antiprotozoal efficacy, with weekly blood count monitoring. Vitamin K has no role, and substituting clindamycin is done for sulfa intolerance such as severe rash, not marrow toxicity.

Reference: Nelson Textbook of Pediatrics, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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