Could contracts between pharmaceutical firms and french veterinarians bias prescription behaviour: A principal-agency theory approach in the context of oligopolies

In France, veterinarians can both prescribe and deliver veterinary medicines, which is a questionable situation from the perspective of antimicrobial use (AMU) reduction to avoid antimicrobial resistance (AMR). This situation places veterinarians in direct commercial relationships with the pharmaceutical industry as purchase contracts are signed between veterinarians and pharmaceutical companies. The aim of the present work is to analyse the relationships between veterinarians and pharmaceutical firms in the oligopoly market context of French veterinary medicine to determine whether the prescription behaviour of practitioners can be biased by joint prescription and delivery. Therefore, we develop an analysis based on principal-agent theory. Contracts between pharmaceutical companies and veterinarians during the 2008–2014 period were analysed based on 382 contracts related to 47 drugs belonging to eight main pharmaceutical firms (2320 observations). The price per unit after rebate of each drug and contract was calculated. The descriptive analysis demonstrated high disparity among the contracts across pharmaceutical firms with regard to the provisions of the contracts and how they are presented. Then, linear regression was used to explain the price per unit after rebate based on the explanatory variables, which included the yearly purchase objective, year, type of drug and type of rebate. The decrease in price per unit after rebate for each extra €1000 purchase objective per drug category was established to be €0.061 per 100 kg body weight for anticoccidiosis treatments, €0.029 per 100 kg body weight for anti-inflammatories, €0.0125 per 100 kg body weight and €0.0845 per animal for antiparasitics, and €0.031 per animal for intramammary antimicrobials. Applying agency theory reveals that veterinarians can be considered agents in the case of monopolistic situations involving pharmaceutical firms; otherwise, veterinarians are considered principals (oligopolistic situations in which at least several medicines have similar indications). The present study does not provide evidence suggesting that joint prescription and delivery may introduce any potential prescription bias linked to conflicts of interest under the market conditions during the 2008–2014 period.