Prophylaxis for PCP in HIV infection?

• A. Dapsone
• B. TMP-SMX
• C. Azithromycin
• D. Clindamycin

Answer: (B)

Pneumocystis jirovecii pneumonia (PCP) prophylaxis is recommended in HIV when the CD4 count falls below 200 cells/µL or if there’s a history of PCP. The best choice for prophylaxis is trimethoprim-sulfamethoxazole because it is highly effective at preventing PCP and, in those with very low CD4 counts, also helps prevent toxoplasma encephalitis. A common prophylaxis regimen is a double-strength TMP-SMX tablet daily or three times a week, adjusted for kidney function and tolerance.

If a patient cannot take sulfa drugs, alternatives include dapsone, atovaquone, or inhaled pentamidine, each with its own caveats (for example, dapsone requires G6PD screening and can cause hematologic issues; atovaquone is less potent; inhaled pentamidine can cause bronchospasm). Azithromycin is used for MAC prophylaxis, not PCP, and clindamycin is not used for PCP prophylaxis (though it’s part of a treatment option with primaquine in sulfa-allergic patients).