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A pharmacokinetic model to document the actual disposition of topical ivermectin in cattle

Publication Date
DOI: 10.1051/vetres:2003014
  • [Sdv:Bbm:Bm] Life Sciences/Biochemistry
  • Molecular Biology/Molecular Biology
  • [Sdv:Bbm:Bm] Sciences Du Vivant/Biochimie
  • Biologie Moléculaire/Biologie Moléculaire
  • [Sdv:Gen:Ga] Life Sciences/Genetics/Animal Genetics
  • [Sdv:Gen:Ga] Sciences Du Vivant/Génétique/Génétique Animale
  • [Sdv:Bc] Life Sciences/Cellular Biology
  • [Sdv:Bc] Sciences Du Vivant/Biologie Cellulaire
  • [Sdv:Bc:Ic] Life Sciences/Cellular Biology/Cell Behavior
  • [Sdv:Bc:Ic] Sciences Du Vivant/Biologie Cellulaire/Interactions Cellulaires
  • [Sdv:Mp] Life Sciences/Microbiology And Parasitology
  • [Sdv:Mp] Sciences Du Vivant/Microbiologie Et Parasitologie
  • [Sdv:Imm] Life Sciences/Immunology
  • [Sdv:Imm] Sciences Du Vivant/Immunologie
  • [Sdv:Neu] Life Sciences/Neurons And Cognition
  • [Sdv:Neu] Sciences Du Vivant/Neurosciences
  • [Sdv:Spee] Life Sciences/Santé Publique Et épidémiologie
  • [Sdv:Spee] Sciences Du Vivant/Santé Publique Et épidémiologie
  • [Sdv:Ba] Life Sciences/Animal Biology
  • [Sdv:Ba] Sciences Du Vivant/Biologie Animale
  • Ivermectin
  • Pour-On
  • Cattle
  • Licking Behaviour
  • Pharmacokinetics
  • Biology
  • Medicine
  • Pharmacology


Ivermectin is a worldwide-used antiparasitic drug largely administered to cattle as a topical formulation (pour-on). The actual plasma and faecal disposition of pour-on ivermectin in cattle was documented using an original pharmacokinetic model, and taking into account the oral ingestion of the topical drug following physiological licking as a secondary route of exposure. Six pairs of monozygotic twin cattle received successively one i.v. and two pour-on administrations of ivermectin at a 3-5-month interval. For one pour-on administration, the twins were separated into an unrestrained group and a group where self- and allo-licking were prevented. Ivermectin concentrations in the plasma and faeces were determined by HPLC. Licking resulted in a high intra-and inter-individual variability of systemic exposure after topical application. By the means of pharmacokinetic modelling, we showed that 58-87% of the pour-on dose was ingested, while only 10% was absorbed percutaneously. Approximately 72% of the ingested ivermectin transited directly into the faeces, resulting in a 7-fold higher faecal excretion of the parent drug than in the non-lickers. We conclude that topical administration does not guarantee a controlled drug delivery in cattle. More importantly, the simulations revealed that non-treated cattle could get easily contaminated by allo-licking, raising the public health problem of unexpected drug residues in edible tissues.

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