Cost-effectiveness of Orlistat for the Treatment of Overweight and Obese Patients in Ireland

Objective: To assess the cost-effectiveness of orlistat plus a calorie-controlled diet compared with a calorie-controlled diet alone for the treatment of overweight and obese patients in Ireland.

Design: Economic modelling techniques using published international efficacy data and Irish cost data were used to estimate the cost-effectiveness of orlistat in obese patients when only responders to treatment (ie achieve 5% weight loss after 3 months of treatment) continue orlistat after 3 months. The model incorporated known relationships between weight loss and quality of life (utility) gain, and weight loss and reduction in risk of type 2 diabetes (T2DM) to predict the impact of weight loss on quality-adjusted-life-years (QALYs) gained and on the onset of T2DM. The costs associated with each treatment arm included the acquisition cost of orlistat, cost of a calorie-controlled dietary programme and monitoring and treatment costs associated with T2DM. An Irish health-care perspective was taken for the analysis, based on 2003 costs.

Subjects: Weight loss data on 1386 patients from five pivotal orlistat clinical trials with at least 12 months duration were pooled (two American and three primarily European studies). All the studies were randomized, placebo-controlled, multicentre trials with a similar design. The inclusion criteria were BMI > or =28 kg / m(2), age > or =18 y, no diagnosed T2DM and the ability to lose 2.5 kg in weight during the introductory period.

Measurements: Cost effectiveness was modelled from these data and presented as incremental cost per QALY.

Results: When orlistat treatment plus a calorie-controlled diet was compared with a calorie-controlled diet alone, the incremental cost per year was euro 478. The number needed to treat (NNT) to gain one QALY was estimated to be 35. The incremental cost per QALY gained was within the range considered cost-effective at euro 16,954. Sensitivity analysis demonstrated an incremental cost per QALY of euro 11,000-35,000 under a variety of assumptions.

Conclusions: Our model suggests that orlistat is effective and cost-effective in obese patients, if after 3 months of treatment, only treatment responders continue treatment.