Objective: To assess the adherence and persistence with allopurinol therapy among gout patients and to identify risk factors for therapy discontinuation.
Methods: The study population included adults in Maccabi Healthcare Services, a 2-million member health maintenance organization in Israel, who were diagnosed with gout between 2002 and 2008. Adherence with allopurinol was retrospectively assessed by calculating the proportion of days covered of dispensed prescriptions. Persistence was assessed by calculating the mean proportion of follow-up days covered with allopurinol for every study participant.
Results: A total of 7644 patients were identified. Among men, the incidence of gout was strongly associated with age, ranging from 0.5 per 1000 among adults younger than 45 years to more than 36 per 1000 among elderly men aged 85 or older). A total of 1331 gout patients (17% of the study population) were adherent to allopurinol therapy, 36% and 47% had partial and poor adherence, respectively. Persistence analysis indicated that the average duration until therapy was discontinued was similar among men (358 days) and women (379 days). Women aged 45-64 years, non-married individuals, those of low socioeconomic status and those with lower body weight were more likely to discontinue therapy. Logistic regression (n = 2471, 32% of the study sample) showed a 4.5 risk of non-compliance among 45- to 65-year-old women. Better compliance was achieved among those with comorbidities, particularly among patients with concomitant cardiovascular disease.
Conclusion: Only one out of six gout patients is adherent with allopurinol. Intervention programmes to increase adherence with treatment should focus on high-risk populations.
Keywords: adherence; allopurinol; gout; persistence; uric acid.