Efficacy and safety of rechallenge with low-dose trimethoprim-sulphamethoxazole in previously hypersensitive HIV-infected patients.

OBJECTIVE

This study was undertaken to determine whether patients infected with HIV and with prior hypersensitivity to trimethoprim-sulphamethoxazole (TMP-SMX) can be rechallenged successfully with TMP-SMX, what factors predict successful rechallenge, and whether hypersensitivity is due to TMP or to SMX.

DESIGN

A prospective, open study.

SETTING

A tertiary referral hospital.

PATIENT

Thirty-one HIV-infected patients with a history of non-life-threatening hypersensitivity to TMP-SMX.

INTERVENTIONS

Patients received TMP (300 mg twice a week) for 2 weeks and, where no major reaction occurred, subsequently with TMP-SMX (160 and 800 mg per tablet, one tablet two times a day, twice a week). Patients who developed significant and persistent hypersensitivity ceased SMX and were subsequently challenged with TMP-dapsone (300 and 100 mg, respectively, twice a week).

MAIN OUTCOME MEASURES

That rechallenge is more likely to be successful in those with advanced HIV disease.

RESULTS

Five out of 31 (16%) patients developed hypersensitivity to TMP, and two ceased TMP as a result. Fifteen of the 26 (58%) patients who received subsequent TMP-SMX developed hypersensitivity, 12 of whom ceased TMP-SMX because of this reaction. Hypersensitivity to TMP-SMX was significantly less common in those with a CD4+ cell count < 20 x 10(6)/l than in those with a CD4+ cell count > 20 x 10(6)/l (31 versus 85%; P = 0.03). Hypersensitivity to TMP-dapsone occurred in two out of nine patients with hypersensitivity to TMP-SMX on rechallenge. One patient developed transient dyspnoea following a dose of SMX, but no other serious adverse drug reaction occurred.

CONCLUSIONS

Rechallenge with TMP-SMX appears safe in HIV-infected patients with a history of non-life-threatening hypersensitivity and is most likely to be successful in patients with a low CD4+ lymphocyte count. The data suggest a low rate cross-hypersensitivity between SMX and dapsone, at least at the doses used.