P427. Non-adherence and 5-ASA switches in stable IBD patients are associated with increased risk of relapse
A. Robinson1, M. Hankins2, G. Wiseman3, M. Jones4, 1Salford Royal NHS Foundation Trust, Salford, United Kingdom, 2University of Southampton, Southampton, United Kingdom, 3Medical Affairs, Warner Chilcott UK Ltd, Weybridge, United Kingdom, 4Health Informatics Research, Sciensus Ltd, Brighton, United Kingdom
Long-term therapy with 5-ASA is a crucial strategy for obtaining stable symptom control and preventing relapses in inflammatory bowel disease (IBD). Factors which disrupt consistent 5-ASA delivery such as non-adherence are associated with an increased risk of relapse. There is debate about whether 5-ASA formulations should be considered non-interchangeable due to their unique release profiles. The aim of this study was to verify the impact of non-adherence on relapse risk in a UK population, and to evaluate whether changes in 5-ASA formulation increase the risk of relapse.
A retrospective cohort study was conducted using a UK pharmacy dispensing database. Adults who received continuous treatment with Asacol® (mesalazine) 400 mg or 800 mg oral tablets during a 6 month baseline period were followed for 18 months. Adherence was measured using the medication possession ratio (MPR); MPR ≥80 was classed as adherent. In this study, a doubling of MPR (peak MPR, indicating a doubling of 5-ASA dose) was used as a proxy for relapse. Switch was identified as a change to another oral 5-ASA. Relationships between adherence, switch and relapse were examined using cohort, nested case-control and subgroup analyses, controlled for age and gender.
1,731 patient records were extracted, of which 568 patients received Asacol and had complete baseline and follow-up data (age, sex, interpretable MPR) for inclusion in the analysis (mean age 56 yrs, 51.2% male). There was a significant association between relapse and adherence during the follow-up period (RR 1.44, 95% CI 1.08–1.94; p = 0.014), indicating a relapse was more likely with lower adherence (mean MPR). In a subgroup of Asacol patients adherent in the baseline period (n = 276), switching medication was significantly associated with relapse in the follow-up period: 26.3% (62/236) who switched suffered relapses, compared to 7.5% (3/40) of those who did not switch (RR 3.5, 95% CI 1.16–10.62; p = 0.008).
Non-adherence to mesalazine significantly increased the likelihood of relapse in this UK population. Moreover, in this study, adherent patients switched to another 5-ASA had a 3.5 times greater risk of relapse compared to non-switched patients. This analysis represents the first evaluation of the impact of 5-ASA switch using a proxy for relapse in a non-clinical setting. These data may have substantial implications for disease management, but before making firm conclusions, further research is needed.