Pharmacokinetic profiles of three dose rates of morphine sulfate following single intravenous, intramuscular, and subcutaneous administration in the goat

Emma Gordon, School of Veterinary Science, Massey University, University of New Zealand, Palmerston North, New Zealand.
Levent Dirikolu, Comparative Biomedical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, Louisiana, USA.
Chin-Chi Liu, Department of Veterinary Clinical Services, School of Veterinary Medicine, Louisiana State University, Baton Rouge, Louisiana, USA.
Alexander V. Ulanov, Metabolomics Lab, Roy J. Carver Biotechnology Center, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.
Zhong Li, Metabolomics Lab, Roy J. Carver Biotechnology Center, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.
Matt Welborn, Department of Veterinary Clinical Services, School of Veterinary Medicine, Louisiana State University, Baton Rouge, Louisiana, USA.
Chance Armstrong, Department of Veterinary Clinical Services, School of Veterinary Medicine, Louisiana State University, Baton Rouge, Louisiana, USA.
Danielle Vallotton, Department of Veterinary Clinical Services, School of Veterinary Medicine, Louisiana State University, Baton Rouge, Louisiana, USA.
Sarah Keeton, Department of Veterinary Clinical Services, School of Veterinary Medicine, Louisiana State University, Baton Rouge, Louisiana, USA.
Sarah Camlic, Department of Veterinary Clinical Services, School of Veterinary Medicine, Louisiana State University, Baton Rouge, Louisiana, USA.
Clare M. Scully, Department of Veterinary Clinical Services, School of Veterinary Medicine, Louisiana State University, Baton Rouge, Louisiana, USA.

Document Type

Article

Publication Date

1-1-2022

Abstract

This study aimed to evaluate pharmacokinetic profiles of morphine in goats following a single dose administered intravenously, intramuscularly, or subcutaneously at 0.1 mg/kg, 0.25 mg/kg, and 0.4 mg/kg. Study population included eight healthy adult goats in a randomized cross-over study. Serial plasma samples were collected and morphine was quantified using high-performance liquid chromatography/mass spectrometry. Data fit a two-compartment model following intravenous administration and a non-compartmental model following both intramuscular and subcutaneous administration. Plasma elimination half-life was 2.88 ± 1.13 h (0.1 mg/kg), 2.30 ± 0.49 h (0.25 mg/kg), and 2.67 ± 0.82 h (0.4 mg/kg) following IV morphine. Intramuscular C values were 13.4 ± 2.77 ng/ml (0.1 mg/kg), 34 ± 11.50 ng/ml (0.25 mg/kg), and 68.9 ± 24.5 ng/ml (0.4 mg/kg). Intramuscular T f(h) or IM dosing (in hrs) was 0.19 ± 0.14 (0.1 mg/kg), 0.24 ± 0.24 (0.25 mg/kg), and 0.21 ± 0.24 (0.4 mg/kg). Subcutaneous C values were 9.88 ± 3.31 ng/ml (0.1 mg/kg), 28.5 ± 11.6 ng/ml (0.25 mg/kg), and 39.4 ± 14.3 ng/ml (0.4 mg/kg). Subcutaneous T (h) values for SC dosing were 0.36 ± 0.21 (0.1 mg/kg), 0.31 ± 0.17 (0.25 mg/kg), and 0.4 ± 0.13 (0.4 mg/kg). Intramuscular bioavailability values were 153.77 ± 12.60% (0.4 mg/kg), 104.8 ± 25.12% (0.25 mg/kg), and 100.7 ± 29.57% (0.1 mg/kg). Subcutaneous bioavailability values were 130.58 ± 19.07% (0.4 mg/kg), 116.6 ± 27.03% (0.25 mg/kg), and 111.6 ± 23.24% (0.1 mg/kg). No adverse effects were observed. Assuming plasma concentration required to induce analgesia is 16 ± 9 ng/ml in goats, as demonstrated in humans, it is suggested to administer morphine intramuscularly at 0.4 mg/kg every 3-4 h or SC every 2-3 h. This is a speculative conclusion therefore further studies evaluating pharmacodynamics and plasma analgesic threshold in goats is recommended.

Publication Source (Journal or Book title)

Journal of veterinary pharmacology and therapeutics

First Page

107

Last Page

116

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