Pattern of utilization of rifabutin for prophylaxis of Mycobacterium avium complex among patients with advanced human immunodeficiency virus disease in a community setting

Abstract

Objective: To characterize the pattern of utilization, effectiveness, and safety profile of rifabutin for Mycobacterium avium complex (MAC) prophylaxis among individuals with advanced human immunodeficiency virus disease in a community setting.

Methods: Individuals who, while registered in the provincial drug distribution program, had at least one CD4 count below 100 cells/mm3 for the period 1 May 1993 to 31 March 1994 were included. MAC diagnoses were identified through a record linkage with the mycobacterial reference laboratory of the Provincial Centre for Disease Control. In order to determine the occurrence of adverse events, a survey was sent in March 1994 to the 98 primary care physicians prescribing rifabutin prophylaxis in the province. We achieved 100% response rate to the survey.

Results: During the study period 515 patients in our drug treatment program were eligible to receive MAC prophylaxis. Of these, 340 (66%) were being prescribed rifabutin as recommended by current guidelines. Rifabutin prophylaxis use was significantly associated with use of antiretroviral therapy. The product limit estimate of the cumulative incidence of MAC at 10 months was 13.0% among those receiving rifabutin prophylaxis. Diagnosis of MAC was significantly associated with a lower baseline CD4 count (cumulative incidence 7.1% and 18.1% for CD4 > or = 50 and < 50 cells/mm3, respectively, P = 0.01). A total of four cases of uveitis, eight cases of pseudo-jaundice, and five cases of arthralgia in 16 patients were identified by our survey.

Conclusion: Our data demonstrates that rifabutin prophylaxis of MAC is being used by approximately 66% of eligible individuals. Rifabutin use was associated with antiretroviral use, which may reflect individuals' attitudes towards medications. Our intention-to-treat analysis, with a 10 month cumulative MAC incidence of 13.0% among those receiving rifabutin prophylaxis, is in keeping with break-through rates previously reported in the context of clinical trials. Our results also support previous observations that the risk of MAC infection greatly increases at CD4 counts < 50 cells/mm3. Rifabutin prophylaxis was generally well-tolerated in our program.