Assessment of adverse drug reactions in psychiatric inpatients with the AMSP drug safety program:: Methods and first results for tricyclic antidepressants and SSRI

The AMSP (Arzneimittelsicherheit in der Psychiatrie) study is a new program for continuous assessment of adverse drug reactions (ADR) in psychiatric inpatients under naturalistic conditions of routine clinical treatment. It is based on the preceding drug surveillance study AMUP (Arzneimitteluberwachung in der Psychiatrie). Currently, 29 hospitals are participating in the study. This paper reports on the methods of the AMSP study and the first findings on the comparative risks of tricyclic antidepressants (TCA) and selective serotonin reuptake inhibitors (SSRI). Data assessment is restricted to "severe" ADR as defined in the study protocol. Drug use is estimated from reference day data. From 1993 to 1997, 896 cases of severe ADR were observed in 48,564 patients (1.84%). SSRI and the new substances mirtazapine and venlafaxine were increasingly used as antidepressants (AD), but TCA were still the most common AD in 1997 (52.1% of all AD patients). Similar rates of ADR were observed for SSRI and TCA (1.7% and 1.5%, respectively, for all cases, 0.9% and 1.0%, respectively, only for cases rated as probable). However, different types of ADR occurred with the two AD subgroups; whereas toxic delirium and increased liver enzymes were the most frequent ADR related to TCA, nondelirious psychic and neurologic ADR predominated with SSRI. The duration of inpatient treatment was considerably longer in patients who experienced an ADR due to TCA or SSRI than in those who did not. The AMSP study promises to contribute greatly to drug safety by providing the relative frequencies of severe ADR from a large-scale database and by improving our knowledge of ADR.