Rapid oral desensitization to trimethoprim-sulfamethoxazole (TMP-SMZ): use in prophylaxis for Pneumocystis carinii pneumonia in patients with AIDS who were previously intolerant to TMP-SMZ.

Trimethoprim-sulfamethoxazole (TMP-SMZ) is the drug of choice as prophylaxis for Pneumocystis carinii pneumonia in patients with AIDS. However, adverse reactions ascribed to TMP-SMZ are common in such patients. We previously described a rapid method of oral TMP-SMZ desensitization in patients with AIDS and varying degrees of intolerance to the drug. To assess the feasibility, safety, and long-term clinical utility of our desensitization protocol, we retrospectively studied 22 consecutive patients who underwent desensitization. Prior to the procedure each of the study subjects had exhibited moderate to severe reactions to TMP-SMZ. Desensitization was successfully completed in 19 (86%) of the patients. The three patients for whom desensitization failed experienced chills and/or vomiting that resolved promptly with symptomatic therapy. One of the 19 patients was unavailable for long-term follow-up. Of the remaining 18 patients, three discontinued taking TMP-SMZ within 2 weeks of desensitization because of macular rash and fever. The other 15 (71%) of the evaluable patients tolerated both desensitization and subsequent prophylaxis and took TMP-SMZ for a mean of 14 months (in some cases, for as long as 41 months). None had P. carinii pneumonia while receiving TMP-SMZ. These results indicate that most patients who are presumed to be TMP-SMZ-intolerant can be rapidly desensitized with oral TMP-SMZ and subsequently receive the drug for protracted periods as effective prophylaxis for P. carinii pneumonia.