Pharmacokinetics and pharmacodynamics of intravenous medetomidine in the horse.
Abstract: To describe the pharmacodynamics and pharmacokinetics following an intravenous (IV) bolus dose of medetomidine in the horse. Methods: Prospective experimental trial. Methods: Eight, mature healthy horses age 11.7 ± 4.6 (mean ± SD) years, weighing 557 ± 54 kg. Methods: Medetomidine (10 μg kg(-1) ) was administered IV. Blood was sampled at fixed time points from before drug administration to 48 hours post administration. Behavioral, physiological and biochemical data were obtained at predetermined time points from 0 minutes to 24 hours post administration. An algometer was also used to measure threshold responses to noxious stimuli. Medetomidine concentrations were determined by liquid chromatography-Mass Spectrometry and used for calculation of pharmacokinetic parameters using noncompartmental and compartmental analysis. Results: Pharmacokinetic analysis estimated that medetomidine peaked (8.86 ± 3.87 ng mL(-1) ) at 6.4 ± 2.7 minutes following administration and was last detected at 165 ± 77 minutes post administration. Medetomidine had a clearance of 39.6 ± 14.6 mL kg(-1) minute(-1) and a volume of distribution of 1854 ± 565 mL kg(-1). The elimination half-life was 29.1 ± 12.5 minutes. Glucose concentration reached a maximum of 176 ± 46 mg dL(-1) approximately 1 hour post administration. Decreased heart rate, respiratory rate, borborygmi, packed cell volume, and total protein concentration were observed following administration. Horses lowered their heads from 107 ± 12 to 20 ± 10 cm within 10 minutes of drug administration and gradually returned to normal. Horse mobility decreased after drug administration. An increased mechanical threshold was present from 10 to 45 minutes and horses were less responsive to sound. Conclusions: Behavioral and physiological effects following intravenous administration positively correlate with pharmacokinetic profiles from plasma medetomidine concentrations. Glucose concentration gradually transiently increased following medetomidine administration. The analgesic effect of the drug appeared to have a very short duration.
© 2011 The Authors. Veterinary Anaesthesia and Analgesia. © 2011 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesiologists.
Publication Date: 2011-11-22 PubMed ID: 22103480DOI: 10.1111/j.1467-2995.2011.00669.xGoogle Scholar: Lookup
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- Journal Article
Summary
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The study describes the behavior and bodily effects of intravenous medication, medetomidine, on horses, alongside the drug’s pharmacokinetics, or how the body responds to and metabolizes the drug.
Objective and Methodology
- The research was a prospective experimental trial conducted on eight healthy, mature horses with an average age of 11.7 years.
- Medetomidine, in a bolus dose, was administered intravenously to the horses and blood samples were taken at fixed points. This was done from before drug administration until 48 hours post-administration.
- Researchers also documented behavioral, physiological, and biochemical data at predetermined times, from zero to 24 hours post-administration.
- To measure pain thresholds, an algometer was used. This tool can measure the horse’s responses to pain-inducing stimuli.
- Medetomidine concentration in the blood samples was calculated using liquid chromatography-Mass Spectrometry and noncompartmental and compartmental analysis.
Results
- Medetomidine showed peak concentration in the bloodstream around 6.4 minutes after administration.
- The last detection of the drug was at approximately 165 minutes post administration.
- The drug had a clearance rate of 39.6 mL kg(-1) minute(-1) and a volume of distribution of 1854 mL kg(-1).
- The elimination half-life of the drug was approximately 29.1 minutes.
- The glucose concentration in the horses increased to a maximum of about 176 mg dL(-1) roughly 1 hour after administration.
- A decrease was observed in heart rate, respiratory rate, borborygmi (rumbling or gurgling noise in the stomach), packed cell volume, and total protein concentration post drug administration.
- Behavioral changes were also documented, including the lowering of the horses’ heads and decreased mobility following the drug administration.
- The drug had an analgesic or pain-relieving effect, as demonstrated by increased mechanical thresholds and decreased sensitivity to sound. However, this analgesic effect was short-lived, lasting only from 10 to 45 minutes after the injection.
Conclusion
- The study concludes that the behavioral and physiological effects observed post drug administration correspond with the pharmacokinetic profiles, derived from plasma medetomidine concentrations.
- A transitory increase in glucose concentration was noted following the administration of medetomidine.
- The analgesic effect of medetomidine, however, was found to have a very short duration.
Cite This Article
APA
Grimsrud KN, Mama KR, Steffey EP, Stanley SD.
(2011).
Pharmacokinetics and pharmacodynamics of intravenous medetomidine in the horse.
Vet Anaesth Analg, 39(1), 38-48.
https://doi.org/10.1111/j.1467-2995.2011.00669.x Publication
Researcher Affiliations
- K.L. Maddy Equine Analytical Chemistry Laboratory, California Animal Health and Food Safety Laboratory, School of Veterinary Medicine, University of California, Davis, CA 95616,, USA.
MeSH Terms
- Analgesia / methods
- Analgesia / veterinary
- Analgesics, Non-Narcotic / blood
- Analgesics, Non-Narcotic / pharmacokinetics
- Analgesics, Non-Narcotic / pharmacology
- Animals
- Blood Glucose / analysis
- Bradycardia / chemically induced
- Bradycardia / veterinary
- Female
- Heart Rate / drug effects
- Horses / metabolism
- Injections, Intravenous / veterinary
- Male
- Medetomidine / blood
- Medetomidine / pharmacokinetics
- Medetomidine / pharmacology
- Respiratory Rate / drug effects
Citations
This article has been cited 11 times.- Cowling N, Woldeyohannes S, Sole Guitart A, Goodwin W. Measurement of Tissue Oximetry in Standing Unsedated and Sedated Horses.. Vet Sci 2021 Sep 22;8(10).
- de Oliveira AR, Gozalo-Marcilla M, Ringer SK, Schauvliege S, Fonseca MW, Esteves Trindade PH, Prospero Puoli Filho JN, Luna SPL. Development and validation of the facial scale (FaceSed) to evaluate sedation in horses.. PLoS One 2021;16(6):e0251909.
- Wiederkehr A, Barbarossa A, Ringer SK, Jörger FB, Bryner M, Bettschart-Wolfensberger R. Clinical Randomized Comparison of Medetomidine and Xylazine for Isoflurane Balanced Anesthesia in Horses.. Front Vet Sci 2021;8:603695.
- de Oliveira AR, Gozalo-Marcilla M, Ringer SK, Schauvliege S, Fonseca MW, Trindade PHE, Puoli Filho JNP, Luna SPL. Development, Validation, and Reliability of a Sedation Scale in Horses (EquiSed).. Front Vet Sci 2021;8:611729.
- Gehlen H, Faust MD, Grzeskowiak RM, Trachsel DS. Association Between Disease Severity, Heart Rate Variability (HRV) and Serum Cortisol Concentrations in Horses with Acute Abdominal Pain.. Animals (Basel) 2020 Sep 2;10(9).
- Tapio H, Raekallio MR, Mykkänen A, Männikkö S, Scheinin M, Bennett RC, Vainio O. Effects of vatinoxan on cardiorespiratory function and gastrointestinal motility during constant-rate medetomidine infusion in standing horses.. Equine Vet J 2019 Sep;51(5):646-652.
- Tokushige H, Okano A, Arima D, Ito H, Kambayashi Y, Minamijima Y, Ohta M. Clinical effects of constant rate infusions of medetomidine-propofol combined with sevoflurane anesthesia in Thoroughbred racehorses undergoing arthroscopic surgery.. Acta Vet Scand 2018 Nov 5;60(1):71.
- Tokushige H, Kushiro A, Okano A, Maeda T, Ito H, Wakuno A, Nagata SI, Ohta M. Clinical evaluation of constant rate infusion of alfaxalone-medetomidine combined with sevoflurane anesthesia in Thoroughbred racehorses undergoing arthroscopic surgery.. Acta Vet Scand 2018 Sep 4;60(1):50.
- Aoki M, Wakuno A, Kushiro A, Mae N, Kakizaki M, Nagata SI, Ohta M. Evaluation of total intravenous anesthesia with propofol-guaifenesin-medetomidine and alfaxalone-guaifenesin-medetomidine in Thoroughbred horses undergoing castration.. J Vet Med Sci 2017 Dec 22;79(12):2011-2018.
- Wakuno A, Maeda T, Kodaira K, Kikuchi T, Ohta M. Anesthetic management with sevoflurane combined with alfaxalone-medetomidine constant rate infusion in a Thoroughbred racehorse undergoing a long-time orthopedic surgery.. J Equine Sci 2017;28(3):111-115.
- Grimsrud KN, Ait-Oudhia S, Durbin-Johnson BP, Rocke DM, Mama KR, Rezende ML, Stanley SD, Jusko WJ. Pharmacokinetic and pharmacodynamic analysis comparing diverse effects of detomidine, medetomidine, and dexmedetomidine in the horse: a population analysis.. J Vet Pharmacol Ther 2015 Feb;38(1):24-34.
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