Metabolism and pharmacokinetics of pharmaceuticals in cats (Felix sylvestris catus) and implications for the risk assessment of feed additives and contaminants. (1st March 2021)

• Record Type: Journal Article
• Authors: Lautz, L.S.; Jeddi, M.Z.; Girolami, F.; Nebbia, C.; Dorne, J.L.C.M.
• Is Part Of: Toxicology letters. Volume 338(2021)
• Page Start: 114
• Page End: 127
• Publication Date: 2021-03-01
• Subjects: Cats -- Pharmacokinetics -- Rats -- Uncertainty factor -- Chemical risk assessment -- Feed additives -- Contaminants; Toxicology -- Periodicals; 363.179
• DOI: 10.1016/j.toxlet.2020.11.014
• Languages: English
• ISSNs: 0378-4274

Abstract

Graphical abstract: Highlights: Review of xenobiotic metabolising enzymes and transporters in cats. Pharmacokinetic data for 30 pharmaceuticals are compared between cats and rats. Uncertainty factors for risk assessment of chemicals in cats are derived. Future work to further characterise xenobiotic metabolism in cats is discussed. Abstract: In animal health risk assessment, hazard characterisation of feed additives has been often using the default uncertainty factor (UF) of 100 to translate a no-observed-adverse-effect level in test species (rat, mouse, dog, rabbit) to a 'safe' level of chronic exposure in farm and companion animal species. Historically, both 10-fold factors have been further divided to include chemical-specific data in both dimensions when available. For cats ( Felis Sylvestris catus ), an extra default UF of 5 is applied due to the species' deficiency in particularly glucuronidation and glycine conjugation. This paper aims to assess the scientific basis and validity of the UF for inter-species differences in kinetics (4.0) and the extra UF applied for cats through a comparison of kinetic parameters between rats and cats for 30 substrates of phase I and phase II metabolism. When the parent compound undergoes glucuronidation the default factor of 4.0 is exceeded, with exceptions for zidovudine and S-carprofen. Compounds that were mainly renally excreted did not exceed the 4.0-fold default. Mixed results were obtained for chemicals which are metabolised by CYP3A in rats. When chemicals were administered intravenously the 4.0-fold default was not exceeded with the exception of clomipramine, lidocaine and alfentanil. The differences seen after oral administration might be due to differences in first-pass metabolism and bioavailability. Further work is needed to further characterise phase I, phase II enzymes and transporters in cats to support the development of databases and in silico models to support hazard characterisation of chemicals particularly for feed additives.