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Pharmacokinetics of intramuscular morphine in the horse

Master of Science / Department of Clinical Sciences / Warren L. Beard / Pharmacokinetics of Intramuscular Morphine in the Horse
Elizabeth Devine, DVM; Butch KuKanich, DVM, PhD, DACVCP; Warren Beard, DVM, MS, DACVS
Objective - To determine the pharmacokinetics of morphine after intramuscular administration in a clinical population of horses
Design – Prospective, clinical study
Animals – Pilot study included 2 normal horses and the clinical study included 75 horses
Procedures – Morphine was administered at 0.1mg/kg, IM and 2-3 blood samples were obtained from each horse at various times from 0-9 hours after administration. Plasma morphine concentrations were measured using liquid chromatography and mass spectrometry.
Results – Data was analyzed using a naïve pooled pharmacokinetic model. The half-life for the elimination phase was approximately 1.5 hours, the volume of distribution (per bioavailability) was approximately 4.5 L/kg and the clearance (per bioavailability) was approximately 35 mL/kg/min. The peak plasma concentration was 21.6 ng/mL and occurred approximately 4 minutes after administration. Plasma concentrations of morphine were below the limit of quantification by 7 hours in 74 horses.
Conclusions and Clinical Relevance – The relatively short half-life of morphine indicates the need for frequent dosing to maintain targeted plasma concentrations. Adverse effects were uncommon in this study and morphine was well tolerated at a dose of 0.1 mg/kg, IM. Morphine may be a useful adjunctive therapy in painful horses, but the variable plasma concentrations suggest the dose and dosing interval may need to be adjusted to the individual patient’s response.

Identiferoai:union.ndltd.org:KSU/oai:krex.k-state.edu:2097/13864
Date January 1900
CreatorsDevine, Elizabeth P
PublisherKansas State University
Source SetsK-State Research Exchange
Languageen_US
Detected LanguageEnglish
TypeReport

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