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Poth MKM, McKemie DS, Traynham M, Kass PH, Knych HK. Concentrations, pharmacokinetics and selected pharmacodynamics of morphine and its active metabolites following oral administration to horses. J Vet Pharmacol Ther 2023. [PMID: 36883679 DOI: 10.1111/jvp.13122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2022] [Revised: 01/25/2023] [Accepted: 02/18/2023] [Indexed: 03/09/2023]
Abstract
The metabolism and pharmacokinetics of intravenous (i.v.) morphine in the horse have been described; however, administration of therapeutic doses has also been associated with neuroexcitation and adverse gastrointestinal effects. In this study, we hypothesized that oral administration would lead to comparable concentrations of morphine and its presumed active metabolite, morphine 6-glucuronide (M6G) without the adverse effects associated with i.v. administration. Eight horses were administered a single i.v. dose of 0.2 mg/kg morphine and oral doses of 0.2, 0.6, and 0.8 mg/kg of morphine in a four-way balanced crossover design, with a 2-week washout period between doses. Concentrations of morphine and metabolites were determined, and pharmacokinetic parameters determined. Physiologic and behavioral outcomes including the number of steps taken, changes in heart rate, and gastrointestinal borborygmi were assessed. Oral administration of morphine resulted in higher concentrations of morphine metabolites, including M6G (Cmax : 11.6-37.8 ng/mL (0.6 mg/kg); 15.8-42.6 ng/mL (0.8 mg/kg)), compared with i.v. Bioavailability was 36.5%, 27.6% and 28.0% for 0.2, 0.6 and 0.8 mg/kg, respectively. Behavioral and physiologic changes were noted in all groups but were less prominent with oral compared with i.v. administration. Results of the current study are encouraging for further study, specifically anti-nociceptive effects of morphine following oral administration.
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Affiliation(s)
- Meghan K M Poth
- K.L. Maddy Equine Analytical Pharmacology Laboratory, School of Veterinary Medicine, University of California, Davis, Davis, California, USA
| | - Daniel S McKemie
- K.L. Maddy Equine Analytical Pharmacology Laboratory, School of Veterinary Medicine, University of California, Davis, Davis, California, USA
| | - Megan Traynham
- K.L. Maddy Equine Analytical Pharmacology Laboratory, School of Veterinary Medicine, University of California, Davis, Davis, California, USA
| | - Philip H Kass
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, Davis, California, USA
| | - Heather K Knych
- K.L. Maddy Equine Analytical Pharmacology Laboratory, School of Veterinary Medicine, University of California, Davis, Davis, California, USA.,Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, Davis, California, USA
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Knych HK, Kanarr K, Fang Y, McKemie DS, Kass PH. Characterization of the pharmacokinetics, behavioral effects and effects on thermal nociception of morphine 6-glucuronide and morphine 3-glucuronide in horses. Vet Anaesth Analg 2022; 49:634-644. [DOI: 10.1016/j.vaa.2022.07.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 07/14/2022] [Accepted: 07/15/2022] [Indexed: 10/16/2022]
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Anderson BJ, Morse JD, Hannam JA, Cortinez LI. Pharmacokinetic and pharmacodynamic considerations of general anesthesia in pediatric subjects. Expert Opin Drug Metab Toxicol 2020; 16:279-295. [PMID: 32148110 DOI: 10.1080/17425255.2020.1739648] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Introduction: The target concentration strategy uses PKPD information for dose determination. Models have also quantified exposure-response relationships, improved understanding of developmental pharmacokinetics, rationalized dose prescription, provided insight into the importance of covariate information, explained drug interactions and driven decision-making and learning during drug development.Areas covered: The prime PKPD consideration is parameter estimation and quantification of variability. The main sources of variability in children are age (maturation) and weight (size). Model use is mostly confined to pharmacokinetics, partly because anesthesia effect models in the young are imprecise. Exploration of PK and PD covariates and their variability hold potential to better individualize treatment.Expert opinion: The ability to model drugs using computer-based technology is hindered because covariate data required to individualize treatment using these programs remain lacking. Target concentration intervention strategies remain incomplete because covariate information that might better predict individualization of dose is absent. Pharmacogenomics appear a valuable area for investigation for pharmacodynamics and pharmacodynamics. Effect measures in the very young are imprecise. Assessment of the analgesic component of anesthesia is crude. While neuromuscular monitoring is satisfactory, depth of anaesthesia EEG interpretation is inadequate. Closed loop anesthesia is possible with better understanding of EEG changes.
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Affiliation(s)
- Brian J Anderson
- Department of Anaesthesiology, University of Auckland, Auckland, New Zealand
| | - James D Morse
- Department of Pharmacology & Clinical Pharmacology, University of Auckland, Auckland, New Zealand
| | - Jacqueline A Hannam
- Department of Pharmacology & Clinical Pharmacology, University of Auckland, Auckland, New Zealand
| | - L Ignacio Cortinez
- División Anestesiología, Pontificia Universidad Católica De Chile, Santiago De Chile, Chile
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