| Summary: | Background: While efavirenz-associated adverse drug events (ADEs) were widely established, the clinical relevance is uncertain. Objectives: We aimed to assess the extent of treatment interruption caused by efavirenz-associated ADEs. Methods: A case-control study of efavirenz recipients who did, versus did not (control) develop adverse drug events (ADE), and who were matched for baseline CD4 + at a ratio of 1:1.3 was conducted. Antiretroviral -naïve patients who were started on efavirenz were followed up retrospectively, and their records scrutinized every month for 2 years. Demographic and clinical predictors of treatment interruption were computed using Cox proportional hazard models. Kaplan- Meier curves were plotted to assess time to treatment interruption for the two groups. Clinical endpoints were: i) efficacy –improved CD4 + counts and/or viral load (VL) suppression, ii) safety –absence of treatment-limiting toxicities, and iii) durability – no interruption until follow-up ended. Results: Both groups had comparable CD4 + counts at baseline (p = 0.15). At t = 24-months, VL in both groups were suppressed to undetectable levels (<20 copies/mL) while median CD4 + was 353 cells/µL (IQR: 249–460). The mean time on treatment was 23 months (95% CI, 22.3 –23.4) in the control group without ADE and 20 months (95% CI, 18.9 – 21.6) in the ADE group (p = 0.001). Kaplan-Meier plots demonstrated that 59.5% of patients who experienced > 1 ADE versus 81% of those who did not experience any ADE were estimated to continue treatment for up to 24 months with no interruption (p = 0.001). Most interruptions to EFV treatment occurred in the presence of opportunistic infections and these were detected within the first 5 months of treatment initiation. Independent predictors which negatively impacted the dependent variable i.e., treatment durability, were intravenous drug use (adjusted hazard ratio, aHR 2.17, 95% CI, 1.03–4.61, p = 0.043), presence of > 1 opportunistic infection(s) (aHR 2.2, 95% CI, 1.13–4.21, p = 0.021), and presence of > 1 serious ADE(s) (aHR 4.18, 95% CI, 1.98–8.85, p = 0.00). Conclusion: Efavirenz’ role as the preferred first-line regimen for South-East Asia's resource-limited regions will need to be carefully tailored to suit the regional population. Findings have implications to policy-makers and clinicians, particularly for the treatment of patients who develop ADEs and opportunistic infections, and for intravenous drug user subgroups. © 2022 The Author(s)
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