Similar Adherence Among Brand and Generic Antiretroviral Drug Regimens

Joseph Rwagitinywa, a doctoral student in pharmacoepidemiology working at Toulouse University Hospital

Joseph Rwagitinywa, PhD

Among patients with HIV, adherence to antiretroviral therapy (ART) is key to viral suppression, while nonadherence has been linked to both drug resistance and disease progression.

With the introduction of single-tablet regimens (STRs) for ART, treatment regimens have been simplified, thereby increasing adherence compared with multi-tablet regimens (MTRs).

At this point in time, STRs for ART are only available as brand-name products. Studies demonstrated that switching patients from brand name STRs to MTRs that may include both brand and generic drugs could generate enormous cost savings. The biggest concern is that the cost savings from switching patients to cheap regimens could be offset by decreased adherence due to higher pill burden and frequency.

Joseph Rwagitinywa, PhD, Pharmacoepidemiology, Toulouse University Hospital in France, led an analysis of real-life adherence rates among patients with HIV in southern France taking ART as either brand STRs, brand MTRs or generic MTRs.

Data for this study were obtained from the health insurance database in Midi-Pyrénées, a region in Southwestern France. This database prospectively collects demographic data (including age and gender), drug details (including NDC, prescription dates and drug quantities) and prescriber information.

"Adherence was measured using Medication Possession Ratio (MPR) calculated by the mean number of days of medication (cART components) supplied within the refill interval divided by the number of days in refill interval," study authors said. "This information was also collected from the national health insurance database."

The study included 1116 patients, who were a median age of 50 years and 32% female. Of the patients included in the study, 165 (15%) were exposed to a generic MTR, 481 (43%) to a brand MTR likely to include a generic in the future, and 470 (42%) to a brand STR.

"The comparison of adherence to generic multi-tablet regimen versus brand multi-tablet regimen and brand single-tablet regimen after controlling for follow up duration and propensity score did not show any significant difference (p=0.4773)," Rwagitinywa and colleagues found.

Unlike previous research into adherence to ART among patients with HIV, Rwagitinywa and colleagues noted, "This was the first study that compared adherence in patients exposed to MTR that incorporate generic ARV [antiretroviral] drugs versus patients exposed to brand MTR and patients exposed to brand STR in real-life and developed world."

Study authors did identify several possible limitations of this study. Presently, there is no gold standard for measuring medication adherence among patients with HIV on ART, which means that different studies may use different methods to measure adherence, generating different results. In addition, this study utilized information available from a database, meaning there was no way to verify whether patients might have filled prescriptions but failed to take all of their doses.

The study, "Comparison of adherence to generic multi-tablet regimens versus brand multi-tablet and brand single-tablet regimens likely to incorporate generic antiretroviral drugs by breaking or not fixed-dose combinations in HIV-infected patients," was published online ahead of print in Fundamental and Clinical Pharmacology.

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