title: Pharmacokinetics and sedative effects of dexmedetomidine in dairy calves.
abstract: OBJECTIVE
  To evaluate the pharmacokinetics of dexmedetomidine (DEX) administered I/V at a dose of 5 µg/kg bodyweight in dairy calves and to compare the sedative effects of anaesthetic protocols involving DEX and xylazine.
  
  
  METHODS
  Nine dairy calves, aged 17-20 days, were treated with 5 µg/kg I/V dexmedetomidine. For pharmacokinetic evaluation, blood samples were collected over 12 hours and serum samples were analysed by high performance liquid chromatography-mass spectrometry. Another nine dairy calves, aged 16-20 days, were treated with 0.2 mg/kg I/V xylazine. After both treatments, heart rate, respiratory rate and rectal temperature were measured for 20 minutes. Sedation quality and recovery times were also assessed.
  
  
  RESULTS
  The kinetics of DEX was best described by a two-compartment model. The distribution and elimination half-lives were 8.7 (SD 5.0) and 83.5 (SD 67.5) minutes, respectively. Mean maximum concentration and body clearance were 12.5 (SD 8.6) ng/mL and 27.9 (SD 13.1) mL/minute/kg, respectively; the mean volume of distribution at steady state was 2,170.8 (SD 1,657.5) mL/kg. A decrease in heart rate was observed after treatments with both DEX and xylazine. No differences in heart or respiration rate, or rectal temperature were observed between the two treatment groups. The onset of sedation occurred after 2.7 (SD 0.67) minutes for calves treated with DEX and 2.8 (SD 0.78) minutes for calves treated with xylazine, and was characterised by a similar degree of deep sedation and ease of handling of the calves. All recoveries were eventless, and no adverse reactions were noted.
  
  
  CONCLUSIONS
  Dexmedetomidine treatment resulted in a reliable and long lasting sedation in calves, a transient decrease in heart rate and no modification in respiratory rate or rectal temperature. The results were comparable to xylazine, the most popular alpha-2-agonist among bovine practitioners. The use of DEX in dairy calves for rapid procedures such as dehorning or castration could be suggested.
authors.affiliation: a Department of Health, Animal Science and Food Safety , Università degli Studi di Milano , Milan 20133 , Italy.
authors.forename: P
authors.initials: P
authors.lastname: Cagnardi
authors.affiliation: a Department of Health, Animal Science and Food Safety , Università degli Studi di Milano , Milan 20133 , Italy.
authors.forename: R
authors.initials: R
authors.lastname: Villa
authors.affiliation: b Department of Veterinary Medicine , Università degli Studi di Milano , Milan 20133 , Italy.
authors.forename: G
authors.initials: G
authors.lastname: Ravasio
authors.affiliation: c Department of Comparative Biomedicine and Food Science , Università degli Studi di Padova , Legnaro (Padua) 35020 , Italy.
authors.forename: L
authors.initials: L
authors.lastname: Lucatello
authors.affiliation: a Department of Health, Animal Science and Food Safety , Università degli Studi di Milano , Milan 20133 , Italy.
authors.forename: F
authors.initials: F
authors.lastname: Di Cesare
authors.affiliation: c Department of Comparative Biomedicine and Food Science , Università degli Studi di Padova , Legnaro (Padua) 35020 , Italy.
authors.forename: F
authors.initials: F
authors.lastname: Capolongo
authors.affiliation: b Department of Veterinary Medicine , Università degli Studi di Milano , Milan 20133 , Italy.
authors.forename: A
authors.initials: A
authors.lastname: Boccardo
authors.affiliation: b Department of Veterinary Medicine , Università degli Studi di Milano , Milan 20133 , Italy.
authors.forename: D
authors.initials: D
authors.lastname: Pravettoni
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002417:Cattle; D016292:Procedural Sedation / Q000379:methods / Q000662:veterinary*; D020927:Dexmedetomidine / Q000097:blood / Q000493:pharmacokinetics* / Q000494:pharmacology; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006993:Hypnotics and Sedatives / Q000097:blood / Q000493:pharmacokinetics* / Q000494:pharmacology; D008297:Male; D056152:Respiratory Rate / Q000187:drug effects; D014991:Xylazine / Q000493:pharmacokinetics / Q000494:pharmacology
chemical_list: D006993:Hypnotics and Sedatives; D014991:Xylazine; D020927:Dexmedetomidine
keywords: Dexmedetomidine; dairy calf; pharmacokinetics; sedative effects; xylazine