Pneumocystis carinii pneumonia and its treatment in patients with AIDS.

Pneumocystis carinii pneumonia (PCP) is the commonest opportunistic infection in AIDS patients. The diagnosis should be strongly suspected in patients who are cyanosed and who present with interstitial pneumonia. The management of PCP in AIDS patients is very similar to that in other groups with the same infection. Trimethoprim-sulphamethoxazole (TMP/SMZ) combinations or pentamidine remain the therapies of choice. Side effects of TMP/SMZ are much greater in AIDS patients than in other immuno-suppressed patients and are similar in frequency to those of pentamidine. Occasionally, pentamidine produces life-threatening complications. Trimetrexate with folinic acid is likely to be as effective against pneumocystis as the two first-line drugs and trimethoprim/dapsone combinations can be given orally and are clearly effective in moderately severe infections. Prophylaxis following an attack of PCP undoubtedly reduces the risk of re-infection, but may not materially alter the overall prognosis. The best drug regimen remains controversial but fortnightly inhaled pentamidine has the advantage of patient acceptability and very low risk of side-effects.