CHARACTERIZING PATTERNS OF DRUG-TAKING BEHAVIOR WITH A MULTIPLE-DRUG REGIMEN IN AN AIDS CLINICAL-TRIAL

Objective: To characterize drug-taking behavior using continuous elect ronic monitoring in an AIDS clinical trial. Setting: This was a substu dy of AIDS Clinical Trials Group (ACTG) protocol 175, a phase II/III s tudy of dideoxynucleoside monotherapy versus combination therapy in as ymptomatic HIV-positive subjects. Participants were required to comply with regimens containing zidovudine, zalcitabine and didanosine, or m atching placebos; the total dairy pill count was 16. Design: For parti cipants at two ACTG 175 sites, electronic devices were used to monitor drug-taking behavior of all study medications over a period of approx imately 90 days. Measurements: Four indices of drug-taking behavior we re calculated and their distributions and relationship to the prescrib ed regimen were examined. Results: Data from 41 subjects were analyzed . Of the prescribed doses of zidovudine, zalcitabine and didanosine, 8 8, 84 and 82%, respectively, were taken. Of these, 55, 66 and 79%, res pectively, were taken at the prescribed dosing frequency. The median p ercentage of days on which participants failed to take any of the dose s was 2-5%. There was a trend towards lower adherence in the combinati on therapy arms compared with those assigned to receive monotherapy. I n this analysis, older patients demonstrated better adherence, althoug h patient characteristics, in general, were poorly predictive of adher ence. Conclusion: Drug-taking behavior for all three active study medi cations differed from that prescribed. One result of this erratic adhe rence was that study participants sustained little antiretroviral effe ct during more than 25% of the monitoring period. (C) 1998 Lippincott Williams & Wilkins.