MEMS devices to measure adherence among HIV infected patients

INTRODUCTION:Adherence with medications is critical if HIV infected patients are to avoid preventable infections and benefit from protease inhibitors and other antiretroviral medication. Little is known about medication adherence in these patients. METHODS: Adherence to medication for PCP prophylaxis was assessed over a six month period among patients enrolled at a hospital based HIV clinic. Medication adherence was quantitated using Medication Event Monitoring System (MEMS) devices, electronic bottle caps that record the date and time that the medication bottle is opened. Percent adherence was defined as the percent of weeks that a patient took medication at least 70% of the time. Patient incentive for the study was the payment of $20 for the return of the cap. RESULTS: Seventy-two patients have completed the study, and data from MEMS devices are available on 62 patients (86%). Six caps (8%) were not returned, and 4 caps (6%) were faulty and could not be read. Adherence rates ranged from 0% to 100%, with a median adherence of 85%. Notably, 25% of patients were adherent less than 50% of the time, and 25% of patients were adherent greater than 94% of the time. There was no association between adherence and income, education, or gender. There was a strong association between adherence and crack cocaine use in the last year. Patients reporting crack cocaine use had a median adherence of 44% compared to 88% among non-users, p=0.007 by Wilcoxan Rank Sum. CONCLUSION: The data indicate MEMS devices are a viable method to measure adherence among HIV infected patients. Rates of adherence with once daily medication varied widely among patients, with a recent history of crack cocaine a predictor of poorer adherence. The relatively low rates of adherence with a simple medication regimen suggest that non-adherence may contribute to morbidity and mortality among HIV infected individuals.