The effectiveness of desensitization versus rechallenge treatment in HIV-positive patients with previous hypersensitivity to TMP-SMX: a randomized multicentric study. C.I.S.A.I. Group. A randomized, pilot trial comparing full versus escalating dose regimens for the desensitization of AIDS patients allergic to sulfonamides. Trimethoprim-sulfamethoxazole (TMP-SMZ) dose escalation versus direct rechallenge for Pneumocystis Carinii pneumonia prophylaxis in human immunodeficiency virus-infected patients with previous adverse reaction to TMP-SMZ.
Our study was undertaken to evaluate if desensitization treatment is more effective than rechallenge in preventing hypersensitivity reactions in HIV-positive patients with previous allergic reactions to TMP-SMX; the secondary aim was to evaluate the frequency of reactions to TMP alone. This was a randomized, multicentre open study. Patients with previous documented hypersensitivity to TMP-SMX who required primary or secondary PCP prophylaxis were enrolled; subjects who had previously had serious adverse reactions to TMP-SMX were excluded. All eligible patients assumed 200 mg TMP for 14 days and in case of no reactions were randomized for desensitization or rechallenge with TMP-SMX. The patients were then followed up by periodical visits for six months. Seventy-three patients were enrolled; 14 subjects (19%) presented reactions on TMP alone during the pre-enrollment phase. The remaining 59 subjects were randomly assigned to the two treatment groups: 34 carried out desensitization (group 1) and 25 rechallenge (group 2) with TMP-SMX. Seven patients in group 1 (20.5%) and seven in group 2 (28%) showed hypersensitivity reactions during treatment; this difference was not statistically significant. No serious reaction occurred in either group. This study showed the comparable effectiveness of the desensitization procedure and rechallenge in patients with a previous, not serious, allergic reaction to TMP-SMX. Sulfonamides are drugs extensively used in the management of AIDS patients. However, the use of sulfonamides is often associated with the development of allergic reactions, provoking the substitution of the drug (by another that may be less effective); alternatively attempts are made to desensitize the patient.
                Compare two drug regimens (full vs. escalating doses) for the oral desensitization of AIDS patients allergic to sulfonamides.
                AIDS patients with previous allergic reactions to sulfonamides and requiring prophylaxis against Pneumocistis carinii, central nervous system toxoplasmosis and diarrhea caused by Isospora belli were randomly assigned to a group receiving a routine dose of cothrimoxazole, or another that received escalating doses of an oral suspension of the same drug, initiating with 75 mg/day of sulfamethoxazole that was doubled every 48 hours till the full dose was reached, if no allergic reaction occurred. Patients were monitored for at least 6 months after enrollment in the trial. The major end-point was the ability to maintain prophylactic treatment after that period of time. Plasma viral load (PVL) and CD(4)/CD(8) counts were measured at baseline. Liver enzymes and hematological parameters were measured at baseline and after 1, 3 and 6 months.
                Eighteen patients were enrolled in the study (15 men and 3 women), with ages ranging from 30 to 57 years (mean 39.9). The mean CD(4) counts were slightly higher for patients receiving a full dose; there was also a trend towards higher baseline CD(8) counts among patients developing new reactions. The mean PVL was similar among the patients in both desensitization groups. The incidence of new allergic reactions was identical (40%) in the two groups. All adverse reactions were mild and no significant increase in liver enzymes were observed.
                Dose regimen is not a predictor of the development of new allergic reactions amongst patients challenged with sulfonamides after an initial allergic reaction. Trimethoprim-sulfamethoxazole (TMP-SMZ) is the most effective Pneumocystis carinii pneumonia (PCP) prophylactic agent, but adverse reactions are common among human immunodeficiency virus (HIV)-infected patients and limit its use. This randomized, double-blind controlled trial compared 2 methods of TMP-SMZ reintroduction, 6-day dose escalation and direct rechallenge, for PCP prophylaxis in HIV-infected patients who had experienced previous treatment-limiting reactions. The primary end point was the ability to take single-strength TMP-SMZ daily for 6 months. Seventy-five percent of the dose-escalation group and 57% of the direct-rechallenge group continued to receive daily single-strength TMP-SMZ for 6 months (P= .014). Among premature discontinuations, 58% of the dose-escalation group and 70% of the direct-rechallenge group were due to adverse reactions. None of these reactions was serious. This study provides evidence that it is possible to successfully reintroduce TMP-SMZ to a significant proportion of HIV-infected patients who have experienced mild-to-moderate treatment-limiting adverse reactions.