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Ophthalmology · Uvea: toxoplasma treatment
Sample itemA patient with sight-threatening toxoplasma retinochoroiditis is started on pyrimethamine and sulfadiazine. Which supplement is added to prevent bone marrow suppression?
Original practice item, not a recalled exam question. Nothing here is recorded.
The answer and the reasoning
D. Folinic acid
Pyrimethamine blocks the parasite dihydrofolate reductase but also depresses the host marrow. Folinic acid bypasses the block in human cells and protects the marrow. Blood counts are monitored during therapy.
Option by option
A. Pyridoxine
Pyridoxine is used to prevent isoniazid neuropathy and has no role here.
B. Vitamin B12
Vitamin B12 does not correct antifolate marrow suppression.
C. Ferrous sulphate
Iron corrects iron deficiency and not antifolate marrow suppression.
D. Folinic acid (correct)
Correct. Folinic acid protects the host marrow from antifolate toxicity.
Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.
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