The AMSP-Project is a prospective multicenter program for continuous assessment of adverse drug reactions of marketed psychotropic drugs in psychiatric inpatients under naturalistic conditions of routine clinical treatment. It corresponds to a dynamic cohort study and currently about 55 German, Swiss and Austrian hospitals are participating, monitoring approximately 30,000 inpatients per year.

to measure the incidence and relative risk ratios of weight gain in association with psychotropic treatment.

All cases of severe weight gain over 10% of initial body weight between the years 2001 through 2005 were reviewed and causality assessment discussed at (inter-)national meetings. Incidence was calculated by number of patients under treatment and relative risks were calculated between the individual treatment regimens.

The risk of severe weight gain is highest under treatment with olanzapine, being responsible for > 40% of the total cases while only 15% of the cohort is treated with olanzapine. The relative risk of olanzapine cases versus the total number of cases was 12 (CI 6.86 – 22.03), taking only those cases into account where only one compound was judged to be responsible (in some cases, drug combinations are imputed.

The AMSP project is a valuable tool in detecting and confirming ADR in a psychiatric hospital setting. The pros and cons of the project are equal to intensive spontaneous monitoring systems. The incidence and relative risk of weight gain is established for psychotropic treatment.

The well known benefits of treatment should be carefully balanced with the problems of weight gain.