An investigation of medication adherence to 5-aminosalicylic acid therapy in patients with ulcerative colitis, using self-report and urinary drug excretion measurements.
BACKGROUND
Non-adherence to 5-aminosalicylic acid (5-ASA) medication can limit the established benefits of this therapy in ulcerative colitis (UC).


AIM
To determine rates and predictors of non-adherence to 5-ASA therapy in UC patients.


METHODS
Medication adherence was assessed using self-report data and urinary drug excretion measurements. Participants completed a study-specific questionnaire and two validated questionnaires: Beliefs about Medicine Questionnaire (BMQ)-Specific and Satisfaction with Information about Medicines Scale.


RESULTS
A total of 169 participants provided self-report adherence data; 151 also provided urine samples. Adherence rates were 111/151 (68%) according to self-report and 90/151 (60%) according to urine analysis, but the two measures were not correlated (chi(2) = 0.12, P = 0.725). Logistic regression identified a significant association between self-reported non-adherence and younger age [odds ratio (OR) for increased age 0.954, 95% confidence interval (CI) 0.932-0.976] and also doubts about personal need for medication (OR for BMQ - Specific Necessity scores 0.578, 95% CI 0.366-0.913). For non-adherence based on urine analysis, only South Asian ethnicity was independently associated with non-adherence (OR 2.940, 95% CI 1.303-6.638).


CONCLUSIONS
Our observations confirm the difficulty of accurately assessing medication adherence. Nonmodifiable (younger age, South Asian ethnicity) and potentially modifiable (medication beliefs) predictors of non-adherence were identified.