Use of dexfenfluramine, fenfluramine and phentermine and the risk of stroke

To estimate the incidence of newly diagnosed idiopathic stroke among users of fenfluramine, dexfenfluramine and phentermine compared to obese nonusers.

We conducted a cohort study with nested case-control analysis utilizing data from the General Practice Research Database in the UK. Eight thousand four hundred and twenty-three subjects aged 69 years or less at the start of follow-up were exposed to at least one of the three study drugs and 17 225 similarly obese subjects were not exposed to any of the study drugs.

We identified 45 incident cases of idiopathic CVA in this cohort of subjects. The incidence of CVA among all current users of a diet drug was 1.3/1000 person-years (95% CI 0.5, 3.5). The incidence for current fenfluramine users (n=2) was 2.6/1000 person-years (95% CI 0.7, 9.6), for current dexfenfluramine users (n=1) 1.1/1000 person-years (95% CI 0.3, 3.8), and for current phentermine users 0/1000 person-years (95% CI 0.0, 12.9). The incidence in obese nonusers was 0.6/1000 person-years (95% CI 0.4, 0. 9). The adjusted matched odds ratio (OR) for thrombotic stroke from the case-control analysis comparing current use of a diet drug to nonuse was 2.4 (95% CI 0.6, 9.1). There was only one exposed subject among seven who had haemorrhagic stroke.

The incidence of CVA in generally young obese subjects during use of fenfluramine, dexfenfluramine or phentermine is low. Although we found an OR of 2. 4 comparing users of any of the anorexiants with nonusers, this is based on only three exposed cases and the confidence limits are wide. We conclude that our study does not support a substantial increased risk of stroke attributable to the use of fenfluramine, dexfenfluramine or phentermine.