Pneumocystis pneumonia (PCP) is a potentially life-threatening infection that occurs in immunocompromised individuals. The nomenclature for the species of Pneumocystis that infects humans has been changed from Pneumocystis carinii to Pneumocystis jirovecii; this was done to distinguish it from the species that infects rats.
HIV-infected patients with a low CD4 count are at the highest risk of PCP. Others at substantial risk include hematopoietic stem cell and solid organ transplant recipients; those with cancer (particularly hematologic malignancies); and those receiving glucocorticoids, chemotherapeutic agents, and other immunosuppressive medications.
The treatment and prophylaxis of PCP in patients without HIV infection will be reviewed here. PCP in HIV-infected patients and the epidemiology, clinical manifestations, and diagnosis of PCP in non-HIV-infected patients are discussed separately. (See "Prophylaxis against Pneumocystis infection in HIV-infected patients" and "Treatment of Pneumocystis infection in HIV-infected patients" and "Epidemiology, clinical manifestations, and diagnosis of Pneumocystis pneumonia in non-HIV-infected patients".)
Trimethoprim-sulfamethoxazole — We recommend trimethoprim-sulfamethoxazole (TMP-SMX) as the treatment of choice for PCP in non-HIV-infected patients (table 1) . Large randomized trials have proven the efficacy of TMP-SMX in patients with HIV infection, whereas efficacy in patients without HIV infection has only been shown in a few small observational studies [2-4] and one comparative randomized trial . (See "Treatment of Pneumocystis infection in HIV-infected patients".)
The standard dose of TMP-SMX is 15 to 20 mg/kg intravenously or orally daily in three or four divided doses (table 1). Dosing of TMP-SMX is based upon the TMP component and expressed as mg/kg per day of TMP. Because TMP-SMX has excellent bioavailability, oral administration is appropriate for all patients who have a functioning gastrointestinal tract.