Excipients of concern in the package inserts of human medicines prescribed in veterinary pharmacotherapy: frequency and implications for animal health

The therapeutic arsenal for veterinary pharmacotherapy includes both medicines for exclusive veterinary use and human medicines prescribed off-label for animals. Unlike medicines for exclusive veterinary use, the package inserts of human medicines detail the qualitative composition of the excipients in these products. Some excipients may cause adverse reactions in specific animal populations, necessitating that healthcare professionals identify and avoid administering medicines containing these excipients to susceptible animals. In this study, we analyzed 120 package inserts for human medicines prescribed for animals and, identified 14 excipients of concern for this population: 10 in liquid products, 6 in semi-solid products, and 5 in solid products. The identified excipients include ethyl alcohol, benzyl alcohol, benzalkonium chloride, mannitol, sodium metabisulfite, sodium lauryl sulfate, propylene glycol, polyethylene glycol, polysorbate, and ethoxylated castor oil. Although off-label use of human medicines in veterinary practice is permitted, the study suggests that regulatory agencies and professional councils should raise awareness among veterinary prescribers and pharmacists regarding these excipients. This unprecedented study highlights the urgent need to address this issue, aiming to encourage research on excipient safety in animal populations and strengthen veterinary pharmacovigilance services.