Background:  Poor adherence to prescribed medications is the most common cause of sub-optimal treatment response. Pill-box organizers are inexpensive and easily used; however, research examining their effect on adherence is extremely sparse.

Methods:  We examined the effect of pill-box organizer use on adherence to ART medications used to treat HIV infection. Data were drawn from 245 subjects followed between 1996 and 2000 in an observational cohort of HIV-infected individuals in San Francisco, California. The primary outcome—adherence—was measured using unannounced, monthly pill counts. Plasma HIV RNA level (viral load) was considered a secondary outcome. Several marginal structural model estimators were used to estimate the effect of pill-box organizer use on adherence and viral suppression, adjusting for confounding by CD4 T cell count, viral load, prior adherence, recreational drug use, demographics, current and past treatment characteristics, and sexual orientation.

Results:  All estimators suggested that pill-box organizer use resulted in approximately 4.1 to 4.5% higher adherence. Pill-box organizer use was associated with a decrease in viral load of between 0.34 and 0.37 log copies/mL, and a 14.2 to 15.7% higher probability of achieving a viral load below 400 copies/mL (OR = 1.8 to 1.9). All estimates of effect were significant and consistent between estimators.

Conclusions:  Pill-box organizers significantly improve adherence to ART and virologic suppression. We estimate that pill-box organizers may be associated with a cost of approximately $19,000 per quality-adjusted life year. Pill-box organizers should be a standard intervention to improve adherence to antiretroviral therapy.