Adherence to weight loss medications; post-marketing study from HMO pharmacy data of one million individuals

Introduction: Post-marketing data on weight-loss medications in free living population are a necessary adjunct to data from clinical trials. Materials and methods: We conducted a population-based analysis of first-time medication users based on HMO pharmacy purchasing data serving > one million adults. Results: During 5 years, usage of orlistat and sibutramine more than doubled and rates were higher during the months May-Aug. As compared to non-users (n=1,038,828), annual weight-loss drug users (n=7175) had higher women proportion, body-mass-index (BMI), bariatric surgery history, and usage of diabetes, depression, and cardiovascular medications (p<0.001 for all). Among users, men had higher BMI (34.4kg/m² vs. 32.5kg/m²), prevalence of diabetes (25.4% vs. 10.7%) and heart disease (14.2% vs. 3.5%) than women. Mean duration of purchasing weight-loss medications was 2.1 months for orlistat and 2.9 months for sibutramine. Fewer than 2% completed 12months of weight-loss medication therapy. Among the 25% who continued to purchase at least 4months, BMI (sub-group analysis) reduced from 33.02kg/m² to 32.04kg/m² (p<0.001). In a multivariate model, long-term adherence (≥4months) to weight-loss medications was associated with use of sibutramine vs. orlistat (OR=2.08; 95%CI: 1.76-2.45), and prevalence of diabetes (OR=1.20; 95%CI: 1.01-1.25). Age, gender, and baseline BMI were not associated with long-term adherence. Conclusions: Usage of weight-loss drugs is higher among diabetes patients. However, the poor adherence to therapy is substantially below levels reported in clinical trials.