Long-term oral mesalazine adherence and the risk of disease flare in ulcerative colitis: nationwide 10-year retrospective cohort from the veterans affairs healthcare system

Abstract

Background: Adherence is a major factor in determining disease activity in ulcerative colitis (UC). There are limited data on long-term nationwide adherence levels among patients with UC.

Aim: To evaluate the long-term adherence levels to oral mesalazine (mesalamine) in the Veterans Affairs (VA) healthcare system, to determine the impact of non-adherence on the risk of flares, and to evaluate the different pharmacy data-based adherence indicators.

Methods: Nationwide data were obtained from the VA for the period 2001-2011. UC patients who started mesalazine maintenance during the inclusion period were included. Level of adherence was assessed using three different indicators: medication possession ratio (MPR), continuous single-interval medication availability (CSA) and continuous multiple-interval medication gaps (CMG). Cox regression modelling was used to predict disease flares and assess the predictive value of each adherence indicator.

Results: We included 13 062 patients into the analysis with median follow-up time of 6.1 years. Percentage of patients with high adherence was 47%, 43%, 31% as identified by CSA, MPR and CMG respectively. Low adherers had a significant increase in the risk of flares compared with high adherers (Hazard ratio: 2.8, 1.7 and 1.8, P < 0.001 for CSA, MPR and CMG, respectively). Compared with other adherence indicators, CSA offered the best trend in predicting disease flares.

Conclusions: Long-term high-adherence level was lower than previously reported. Adherence was a significant factor in predicting disease flares. Pharmacy adherence indicators may be useful to healthcare providers in identifying patients at high risk of exacerbations.