People with HIV who develop Pneumocystis pneumonia (PCP) despite trimethoprim-sulfamethoxazole prophylaxis can usually can be treated effectively with standard treatment doses of trimethoprim-sulfamethoxazole (BIII)

If not already started, antiretroviral therapy should be initiated in patients within 2 weeks of diagnosis of PCP, if possible (AI). 

• Trimethoprim-sulfamethoxazole: (trimethoprim 15–20 mg and sulfamethoxazole 75–100 mg)/kg/day IV given every 6 or 8 hours (AI); may switch to PO formulations after clinical improvement (AI)

• Primaquine* 30 mg (base) PO once daily plus (Clindamycin [IV 600 every 6 hours or 900 mg every 8 hours] or PO [450 mg every 6 hours or 600 mg every 8 hours]) (AI), or
• Pentamidine 4 mg/kg IV once daily infused over at least 60 minutes (AI); may reduce the dose to 3 mg/kg IV once daily in the event of toxicities (BI) or
• Note: Some clinicians prefer primaquine plus clindamycin because it is more effective and less toxic than pentamidine.

Adjunctive Corticosteroids for Moderate-to-Severe PCP Based on the Following Criteria: (AI):

• PaO₂ <70 mm Hg at room air, or
• Alveolar-arterial (A-a) gradient ≥35 mm Hg

Corticosteroid Dosing Schedule

• Prednisone doses (beginning as early as possible and within 72 hours of initiating PCP therapy) (AI):
  • Days 1–5: 40 mg PO twice daily
  • Days 6–10: 40 mg PO daily
  • Days 11–21: 20 mg PO daily
• IV methylprednisolone can be given as 80% of prednisone dose.
• Benefit of corticosteroid if started after 72 hours of PCP treatment is unknown, but some clinicians will use it for moderate-to-severe PCP (BIII).