Long-term adherence to antiretroviral therapy in a South African adult patient cohort: a retrospective study.

BACKGROUND: South Africa has the highest HIV prevalence and supports the largest antiretroviral therapy (ART) programme globally. With the introduction of a test and treat policy, ensuring long term optimal adherence to ART (≥95%) is essential for successful patient and public health outcomes. The aim of this study was to assess long-term ART adherence to inform best practices for chronic HIV care. METHOD: Long-term ART adherence was retrospectively analysed over a median duration of 5 years (interquartile range [IQR]: 5.3-6.5) in patients initially enrolled in a randomised controlled trial assessing tuberculosis and HIV treatment integration and subsequently followed post-trial in an observational cohort study in Durban, South Africa. The association between baseline patient characteristics and adherence over time was estimated using generalized estimating equations (GEE). Adherence was assessed using pharmacy pill counts conducted at each study visit and compared to 6 monthly viral load measurements. A Kaplan Meier survival analysis was used to estimate time to treatment failure. The McNemar test (with exact p-values) was used to determine the effect of pill burden and concurrent ART and tuberculosis treatment on adherence. RESULTS: Of the 270 patients included in the analysis; 54.8% were female, median age was 34 years (IQR:29-40) and median time on ART was 70 months (IQR = 64-78). Mean adherence was ≥95% for each year on ART. Stable patients provided with an extended 3-month ART supply maintained adherence > 99%. At study end, 96 and 94% of patients were optimally adherent and virologically suppressed, respectively. Time since ART initiation, female gender and primary breadwinner status were significantly associated with ≥95% adherence to ART. The cumulative probability of treatment failure was 10.7% at 5 years after ART initiation. Concurrent ART and tuberculosis treatment, or switching to a second line ART regimen with higher pill burden, did not impair ART adherence. CONCLUSION: Optimal long-term adherence with successful treatment outcomes are possible within a structured ART programme with close adherence monitoring. This adherence support approach is relevant to a resource limited setting adopting a test and treat strategy.

Adherence challenges with drugs for pre-exposure prophylaxis to prevent HIV infection.

BACKGROUND: There are 34 million people living with human immunodeficiency virus (HIV) worldwide and each year this number increases. Until a vaccine is discovered, the prevention of new HIV infections remains an urgent priority. Several trials studying the use of oral and topical agents for the prevention of HIV infection have already been completed. Adherence has proved to be a major challenge in achieving product efficacy. AIM OF THE REVIEW: To provide the clinical pharmacist with an understanding of the oral pre-exposure prophylaxis (PrEP) and topical microbicide product pipeline whilst emphasizing the critical importance of adherence to these drugs to avert HIV infection. METHODS: PubMed/Medline and the web-based clinical trials registry (ClinTrials.gov) were searched using appropriate key words. For the time period 1992-2013--all phase II and phase III safety and effectiveness studies--testing agents for prevention of HIV infection were included in the review. Efficacy estimates, adherence estimates and reported challenges with adherence were extracted. RESULTS: Twenty-four phase II and III clinical trials were found during review. Of these, 20 trials have been completed, and six trials show effectiveness in preventing HIV infection. The majority of the successful trials were to oral PrEP and to date only one microbicide trial of a vaginal antiretroviral microbicide gel has showed effectiveness. Adherence to study product played a major role in trial outcomes and there are several reasons for non-adherence. These include high on-trial pregnancy rates, low trial retention rates, low participant perception of risk, participant characteristics such as age <25 years, single status, migratory partners and trial fatigue. Study product characteristics such as dosage form, dosing interval, as well as associated adverse events may also influence adherence. CONCLUSION: Moderate to high adherence is critical to demonstrate efficacy of drugs for HIV prevention. For topical agents, intermittent use associated with coitus is more effective than daily use, particularly if sex is infrequent or partners migrant. For oral agents, daily use is effective but the motivation to use the drug and high risk perception is important. In serodiscordant couples, early initiation of highly active antiretroviral therapy in the infected partner affords almost complete protection to the negative partner. Drugs need to be tailored to the population at risk and availability of multiple drug options are important.