Medication adherence to inflammatory bowel disease medications in Aotearoa New Zealand and correlation with health outcomes: A nationwide database analysis

Abstract

Aims: Inflammatory bowel disease (IBD) management entails long-term medication therapy. Worse disease outcomes and reduced quality of life might arise from poor medication adherence (MA). This study is the first to investigate patients with IBD's adherence across Aotearoa New Zealand and its relationship with disease outcomes. Methods: Dispensing claims data (Pharmaceutical Collection) were used to calculate (3- and 5-year) adherence, using daily polypharmacy possession ratio. Using hospitalization data (National Minimum Dataset), the relationship between adherence and the numbers of hospitalizations and corticosteroid dispensings was investigated. Results: In total, 4654 patients (53% female; 55% Crohn's disease [CD], 45% ulcerative colitis [UC]; median age-at-first-dispensing, 43 years) and 3148 patients (54% female; 55% CD, 44% UC; median age-at-first-dispensing, 44 years) were in the 3- and 5-year cohorts, respectively. The 3- and 5-year cohorts had mean 4.6 and 4.2 IBD-related hospitalizations and 6.9 and 9.2 corticosteroid dispensings, respectively. Average adherence estimates were 77.4% (95% confidence interval: 76.9–78.0%) and 74.9% (95% confidence interval: 74.1–75.6%; 3 and 5 years), while 54% and 51% of patients, respectively, had good adherence (MA ≥ 80%). There was no correlation between adherence and the numbers of hospitalizations (Pearson's R = −.0007; P =.65 and R = −.04; P =.02 [3 and 5 years]) and corticosteroid dispensings (R =.08; P =