Increasing body mass index or weight does not appear to influence the association between efavirenz-based antiretroviral therapy and implant effectiveness among HIV-positive women in western Kenya.

OBJECTIVE: Our objective was to evaluate if increasing body mass index (BMI) or weight influences the association between efavirenz-based antiretroviral therapy (ART) and implant effectiveness. STUDY
DESIGN: We conducted a secondary cohort analysis of HIV-positive women aged 15 to 45 years enrolled in HIV care in western Kenya using an implant from January 2011 to December 2015. Implant use, ART regimen and weight were documented at each clinic visit and height at enrollment. We categorized BMI as underweight, normal weight, overweight or obese, and weight as <70 kg or ≥70 kg. Our primary outcome was incident pregnancy diagnosed clinically. We used crude and adjusted Poisson models with robust standard errors to account for covariates and repeated observations to estimate adjusted incident rate ratios (aIRRs).
RESULTS: In this analysis, 12,960 women contributed a total of 11,285 woman-years of observation time while using an implant, with a median of 6.6 months. The aIRRs comparing efavirenz- to nevirapine-based ART groups did not increase as BMI increased; the aIRRs were 2.0 (1.1-3.6) for underweight, 1.9 (1.5-2.5) for normal, 3.1 (1.6-6.0) for overweight and 2.1 (0.6-6.9) for obese women. The aIRRs comparing efavirenz- to nevirapine-based ART groups did not increase as weight increased; the aIRRs were 2.0 (1.6-2.6) for weight <70 kg and 2.1 (1.0-4.5) for weight ≥70 kg.
CONCLUSION: Higher BMI or weight did not appear to modify the relationship between efavirenz use and implant effectiveness. IMPLICATIONS: Programs should not recommend differential counseling for women with higher BMI or weight who concomitantly use implants and efavirenz.