To assess the incidence of hospital admissions related to adverse drug reactions (ADRs) in France and the frequency of preventable ADRs in France, a prospective study was conducted among a representative randomly selected sample of medical wards in public hospitals between December 2006 and June 2007; all patients admitted during a 2-week period were included. An ADR-related hospitalization case was defined as a hospital admission because of an ADR, and an independent committee reviewed and validated all potential cases. Preventability was assessed using the French ADR preventability scale. Data were extrapolated to the population of France. Among 2692 admissions, 97 were related to an ADR (incidence 3.6%, 95% confidence interval, CI [2.8-4.4]). Patients admitted for an ADR were significantly older than those admitted for other reasons (P < 0.001). A third (32.0%) of ADR-related hospitalizations were 'preventable', 16.5% 'potentially preventable'. Drug interactions accounted for 29.9% of ADR-related hospitalizations. The most frequent causes of ADR-related hospitalizations were vascular disorders (20.6%), mainly bleeding complications, central nervous system disorders (11.3%), gastrointestinal disorders, and general disorders (9.3%). Antithrombotic and antineoplastic agents were the most frequently involved (12.6% each), followed by diuretics and analgesics (9.0% each). Vitamin-K-antagonists (VKAs) were the most common drugs associated with admission. The estimated annual number of ADR-related hospitalizations in France was 143 915 (95% CI [112 063-175 766]). ADRs were a significant cause of hospital admission in 2006-2007, in particular those due to VKAs. As new oral anticoagulants (NOACs) have been marketed, more attention needs to be paid to ensure a safe use of antithrombotic agents.

Reimbursement data with an appropriate time frame and interviews estimate exposure to chronically used drugs similarly. Self-medication was better described with interviews whereas reimbursement data seem more useful for drugs used topically or intermittently.