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.