How do veterinarians influence sales of antimicrobials? A spatial-temporal analysis of the French prescribing-delivery complex in cattle.

Background In animal agriculture, antimicrobials (AM) are used to control infectious diseases whose incidence and severity vary across production systems, but may contribute to select AM resistant bacteria, potentially disseminating in humans. Antimicrobial resistance (AMR) represents a public threat, leading policymakers to implement measures to reduce antimicrobial use (AMU). Investigating AMU patterns at prescriber's level, beyond national AMU trends, enables evaluation of substitutions between AM classes (occurring when one product is replaced by another), or average consumption per production system. Our aim was to identify the influence veterinarians would exert on AMU by quantifying substitution between AM products prescribed and delivered in similar therapeutic indications, in cattle production. Methods Monthly sales data on four critically important AM in five French areas (representative of production systems) were analysed from 2008 to 2013. We calculated the animal live weight receiving a treatment course and evaluated substitutions between brand-name and generic products, and between products from different AM classes with similar indications. Results Substitutions occurred, between products of the same class (macrolides) with similar indications, between generic and brand-name products (fluoroquinolones, ceftiofur, florfenicol) and between innovative and brand-name products (marbofloxacin, ceftiofur). Innovative products reaching the market represented between 2% and 40% of the yearly sales for a given molecule, depending on the active ingredient and the area. The introduction of generic products of fluoroquinolones and ceftiofur led to a moderate adoption of the generic product at the expense of the brand-name one, unlike in human health care where the adoption reaches up to 80%. Conclusion Veterinary prescription remains a strong regulating power of AMU; substitutions only occurred for products with similar indications.