Reasons for early abacavir discontinuation in HIV-infected patients

OBJECTIVE: To determine incidence of and reasons for discontinuation of abacavir within the first 6 months of therapy. METHODS: Retrospective study performed in the cohort of HIV-infected adults who started abacavir in a medical unit between 1997 and December 2000. All adverse drug reactions (ADRs) (especially hypersensitivity) observed in this cohort were reported. The association between drugs and complications were evaluated, using the French method to assess unexpected and toxic drug reactions. According to the variables studied, statistical analysis was performed using the chi2 test, Fisher's exact test, Mann-Whitney, Wilcoxon, or Kruskal-Wallis tests. RESULTS: All 331 patients treated with abacavir during this time period were included in this study. Early discontinuation of abacavir was observed in 34.1% of patients, the main reasons being adverse effects (20.8%), virologic failure (3.3%), drug holidays (2.7%), poor adherence (2.7%), and death (1.8%). Adverse effects were mostly represented by hypersensitivity reactions. After retrospective analysis, abacavir was stopped for likely hypersensitivity in 8.5% of patients, for doubtful hypersensitivity in 4.2%, and for other adverse effects in 8.1% of patients. CONCLUSIONS: This study shows that abacavir is mainly stopped during the first 6 months of therapy for ADRs. The rate of likely hypersensitivity reaction observed in this study (8.5%) is higher than that observed in clinical trials (5%). After retrospective evaluation, the causality assessment of abacavir is not always certain.