Changes and predictors for change to thiazolidinedione prescribing in UK primary care following the rosiglitazone safety warning

Objective: To investigate switching from thiazolidinediones, and predictors for switching treatment, after publication of a meta-analysis reporting an increased risk of myocardial infarction associated with rosiglitazone use. Research design and methods: Using the Health Information Network (THIN) UK primary care database, the number of people with type 2 diabetes prescribed either thiazolidinedione, rosiglitazone (n = 10,062) or pioglitazone (n = 4454), and the rate of switching from thiazolidinediones (n = 3301 and 1106, respectively), were computed for each month, May 2006 to January 2008. The probability of switching post-publication, May 2007 to January 2008, was modelled by logistic regression in a forward step-wise model. Variables included demographics, history of ischaemic heart disease (IHD), heart failure (HF) or stroke, risk factors for IHD, glucose-lowering and cardiovascular drug use, HbA(1c) and diabetes duration. Results: There was a sharp increase in switching from both thiazolidinediones in summer 2007; rosiglitazone prescription numbers then decreased while pioglitazone prescribing increased. Switching from rosiglitazone was associated with IHD [adjusted odds ratio (OR) 1.72; 95% confidence intervals (CI) 1.47-2.00], insulin treatment (OR 5.10; 95% CI 3.21-8.10), HF (OR 2.26; 95% CI 1.62-3.18), a recent sulphonylurea prescription (OR 1.33; 95% CI 1.17-1.51) gender (OR men vs. women 0.79; 95% CI 0.70, 0.90) and duration of therapy. Switching from pioglitazone was associated with HF (OR 3.05; 95% CI 1.77-5.26), duration of therapy, and number of glucose-lowering treatments. Conclusions: Prescribing habits for both thiazolidinediones changed immediately following the safety warning. IHD was associated with switching from rosiglitazone; otherwise reasons for change appear to be complex, not directly related to the findings of the meta-analysis.