The effect of number of pills and dosing frequency on antiretroviral drug adherence: An assessment using two adherence monitoring measures

Background: Strict adherence requirement to antiretroviral drugs remains a key determinant of successful treatment outcome. Drug regimen complexity has been identified as a factor that discourages adherence to antiretroviral therapy. Several measures are available to assess drug adherence each with its strengths and weaknesses. Only few of these measures are cost effective and can be used in resource limited settings. Objective: To determine the effect of number of pills, dosing frequency, and concomitant drugs on adherence to antiretroviral drug therapy. Method: This is a cross-sectional study utilizing a semi-structured questionnaire. Adherence to antiretroviral therapy was measured using self-report and prescription refill. The total number of pills and the dosing frequency were calculated and its association with poor adherence tested via a logistics regression model. Results: Majority of the respondents were females (69.5%), aged 31-40 years (42.2%), married (68.5%), had greater than one pill in their drug regimen (84%), were on twice daily regimen (56.4%) and on other non-ARV drugs (59.9%). An assessment of the adherence levels showed that 140(37.4%) and 161(43%) of the interviewed patients had poor adherence level of ≤ 95% as measured via self-report and pharmacy pick up respectively. At multivariate analysis taking other non-ARV drugs and taking 2 or more ARV pills were predictors of poor adherence to antiretroviral drugs (OR=9, 4.8-16.69) and (OR=0.19, 0.08-0.5) respectively. Conclusion: The number of times drugs are taken in a day did not affect adherence in this study however, increased number of pills and addition of other concomitant medications to an antiretroviral regimen discouraged adherence.