A controlled trial of trimethoprim-sulfamethoxazole or aerosolized pentamidine for secondary prophylaxis of Pneumocystis carinii pneumonia in patients with the acquired immunodeficiency syndrome. AIDS Clinical Trials Group Protocol 021.

BACKGROUND

Pneumocystis carinii pneumonia (PCP) continues to be the most common index diagnosis in the acquired immunodeficiency syndrome (AIDS), but it is not clear which of several available agents is the most effective in preventing a recurrence of PCP.

METHODS

We conducted a comparative, open-label trial in 310 adults with AIDS who had recently recovered from an initial episode of PCP and had no treatment-limiting toxic effects of trimethoprim-sulfamethoxazole or pentamidine. All the patients were treated with zidovudine and were randomly assigned to receive either 800 mg of sulfamethoxazole and 160 mg of trimethoprim once daily or 300 mg of aerosolized pentamidine administered every four weeks by jet nebulizer. The participants were followed for a median of 17.4 months.

RESULTS

In the trimethoprim-sulfamethoxazole group (n = 154) there were 14 recurrences of PCP, as compared with 36 recurrences (including 1 extrapulmonary recurrence) in the aerosolized-pentamidine group (n = 156). The estimated recurrence rates at 18 months were 11.4 percent with trimethoprim-sulfamethoxazole and 27.6 percent with pentamidine (P < 0.001). The risk of a recurrence (adjusted for initial CD4 cell count) was 3.25 times higher in the pentamidine group (P < 0.001, 95 percent confidence interval, 1.72 to 6.16). There were no significant differences between the groups in survival or in hematologic or hepatic toxicity. Crossovers from trimethoprim-sulfamethoxazole to aerosolized pentamidine were more common than the reverse (27 vs. 4 percent), partly because of the study protocols for the management of leukopenia. There were 19 serious bacterial infections in the trimethoprim-sulfamethoxazole group and 38 in the pentamidine group. The time to a first bacterial infection was significantly greater for those assigned to trimethoprim-sulfamethoxazole (P = 0.017).

CONCLUSIONS

In patients with AIDS who are receiving zidovudine, trimethoprim-sulfamethoxazole is more effective than aerosolized pentamidine in conventional doses for the prevention of recurrent pneumocystis infection.