Difference in persistence between tablets and capsules.

Abstract

e18894 Background: More recently, pharmaceutical companies have developed capsule and tablet forms of their drugs to allow a choice on dosage form. As both capsules and tablets should be bioequivalent, adherence rates between members prescribed capsules and tablets should be the same. This study compares persistency between capsule and tablet forms of enzalutamide and palbociclib. Methods: This retrospective cohort study included adult Caremark members who received enzalutamide and palbociclib between 03/01/2021 and 03/01/2022 with continuous eligibility for six months prior and 12 months post-index into the study. Members were excluded if they had a > 60-day gap in fill or switched from a capsule to a tablet or vice versa during the study period. Adherence was measured using the prescription-based proportion of days covered (PDC) and defined as the sum of days with medication on hand divided by the number of days between index fill and exhaust of last fill. Continuous variables were compared with the student’s t-test and Mann-U tests; categorical variables were compared with a chi-square test. Logistic regression was utilized to assess adherence differences in capsules vs. tablets; p-values < 0.05 were significant. Results: 5,997 members were included in the enzalutamide cohort; there were no insurance type or region differences (all p > 0.05) between members receiving capsules and tablets. There were no significant differences in mean PDC (mean (SD) 0.963 (0.080) vs. 0.964 (0.073); p = 0.521) or adherence rates (94.2% vs. 95.2%); p = 0.215) between members receiving capsules and tablets. After adjusting for the variables in the model, there was no difference in adherence rates between tablets and capsules. Members less than 65 years of age had significantly lower adherence rates (odds ratio (OR)) 0.5 (95% confidence interval (CI), 0.35-0.71) compared to those aged 65-74. 5,361 members were included in the palbociclib cohort; there were significant differences in age, gender, type of insurance and region (all p < 0.05) between members receiving capsules and tablets. There were no significant differences in PDC (0.962 (0.072) vs. 0.960 (0.072); p = 0.534) or adherence rates (94.9% vs. 94.9%); p = 1.0) between members receiving capsules and tablets. Conclusions: In this study, capsule and tablet forms of enzalutamide and palbociclib had similar adherence rates when adjusting for confounders.