PHP185 - Patterns of Non-Adherence to Oral Antiviral Drugs

Abstract

Even if a patient misses a number of doses of a once-daily oral drug, the therapeutic effect will be maintained if there are no occurrences of consecutively missed doses that exceed the duration of the drug’s effect. We previously calculated the frequency of consecutively missed doses values of ≥2, ≥3, and ≥4 within a 30-day period with the assumption that distributions of missed doses were purely random (Clin Pharmacokinet [2017] 56; 1435-1440). Here, we determine the observed frequencies of ≥2, ≥3, and ≥4 consecutively missed doses using data recorded from patients taking a once daily oral anti-HIV drug. Medication event monitoring system (MEMS) data were extracted from the iAdherence online database for a 30-day period for 555 patients taking once-daily HIV drug therapy. We recorded the number of days with missed doses and occurrences of ≥2, ≥3, or ≥4 consecutively missed doses. The observed frequencies of ≥2, ≥3, and ≥4 consecutively missed doses were compared to a theoretical random distribution of misses using the Wilcoxon signed-rank test. The frequencies of 0, 1, and ≥2 missed daily doses were 0.279, 0.312, and 0.409, respectively. The frequencies of ≥2, ≥3, and ≥4 consecutively missed doses were 0.184, 0.110, and 0.065, respectively. The probabilities that the observed frequencies of ≥2, ≥3, and ≥4 consecutively missed doses were as expected from a random distribution of missed doses were P=0.345, P<0.01, and P<0.01, respectively. Observed runs of ≥3 and ≥4 consecutively missed doses—and hence loss of therapeutic effect for drugs of duration of action of <3 and <4 days, respectively—occurred more frequently than expected if missed doses were randomly distributed.