IS THE INCIDENCE OF UPPER RESPIRATORY-TRACT INFECTION INDEPENDENT OF DRUG-TREATMENT IN LARGE COHORT STUDIES OF LONGER TERM USE DRUGS

In observational cohort studies which monitor drug safety, the pattern s of reported events are likely to be influenced by a number of factor s. We hypothesized that the distribution of events which are unlikely to be adverse events associated with drug use, differ from that for ev ents which may be adverse drug reactions. In 39 individual Prescriptio n-Event Monitoring (PEM) studies, the incidence rates for upper respir atory tract infections (URTI) and back pain, in the first month of tre atment and in the subsequent 5 months, were compared to those for naus ea/vomiting and malaise/lassitude. For URTI and back pain there was no statistically significant difference in the event rates between these time periods. This pattern may be characteristic of events which are independent of the disease being treated and are unlikely to be advers e events associated with drug use. However, for nausea/vomiting and ma laise/lassitude, which can be adverse events associated with drug trea tments, the event rates in the first month of treatment were significa ntly greater than in subsequent months. These observations confirm tha t doctors are reporting events irrespective of whether or not they sus pect the event to be an adverse event associated with the drug. This p rovides a simple validation of the PEM methodology. (C) 1998 John Wile y & Sons, Ltd.