Letigen® and Cardiovascular Morbidity. A Register-Based Epidemiological Study

Letigen® was a combination drug containing ephedrine, an adrenergic agonist with lipolytic and appetite-inhibiting properties. The drug was used as adjuvant treatment of obesity from 1990 and up to 2002 when it was withdrawn from the market by the manufacturer. The basis for this was a number of spontaneous reports about patients that died during treatment with Letigen®.

The causal relation has never been addressed. There are only sparse data from randomised studies and the above-mentioned reports are not conclusive.

We propose a controlled study based on data from Statistics Denmark that hold a complete copy of the Prescription Register of the Danish Medicines Agency and the Danish Hospital Discharge Register. The aim of the study would be to determine whether there is an excess frequency of deaths and serious cardiovascular events that can not be explained by particular characteristics of users of the drug. A well-known problem in such observational studies is a fundamental incomparability between users and non-users of drugs. In the present setting, it should be expected that use of Letigen® is associated with high BMI, smoking, alcohol abuse, type-2 diabetes, mild hypertension, low physical activity and other indicators of unhealthy lifestyle. Thus, an uncritical comparison between users and non-users of Letigen® regarding serious cardiovascular events will probably show an excess frequency that can not necessarily be attributed to the drug. This problem can be addressed by a special epidemiological technique - the case-crossover design - which is particularly robust to such comparability problems. In brief, only cases should be included. Controls are the same persons at an earlier time, , where the case-defining disease has not yet developed. The exposure of cases will be compared with the exposure of the same persons' case history.

To account for the effect of chronic exposure, we also perform, as a secondary analysis, a conventional case-control study nested within the cohort of Letigen users, and employing a risk-set sampling technique.