Adjunctive folinic acid with trimethoprim-sulfamethoxazole for Pneumocystis carinii pneumonia in AIDS patients is associated with an increased risk of therapeutic failure and death.

Ninety-two AIDS patients with Pneumocystis carinii pneumonia (PCP) were randomized to receive folinic acid or matching placebo in conjunction with trimethoprim-sulfamethoxazole in a prospective, double-blind trial. Neither frequency of dose-limiting toxicity (26% vs. 37%; P = .4) nor time to occurrence (P = .7) was associated with folinic acid use. Although incidence of neutropenia was lower in patients receiving folinic acid (23% vs. 47%; P = .03), time to occurrence of neutropenia did not differ (P = .4). Seven (7.6%) of 92 patients with confirmed PCP met criteria for therapeutic failure, and 5 (6%) died during therapy. Surprisingly, folinic acid use was associated with a higher rate of both therapeutic failure (15% vs. 0; P = .01) and death (11% vs. 0; P = .06). Time to therapeutic failure was shorter and probability of death greater in patients receiving folinic acid (P = .005, P = .02, respectively), even when adjusted for baseline arterial oxygen pressure, serum lactate dehydrogenase, respiratory rate, CD4 cell count, and peak serum level of trimethoprim or sulfamethoxazole.