Presented in part at the 2007 AVA/ECVAA Autumn Meeting, Leipzig, Germany.
Comparison of the cardio-respiratory effects of methadone and morphine in conscious dogs††
Article first published online: 4 DEC 2008
© 2008 The Authors. Journal compilation © 2008 Blackwell Publishing Ltd
Journal of Veterinary Pharmacology and Therapeutics
Volume 32, Issue 4, pages 317–328, August 2009
How to Cite
MAIANTE, A. A., TEIXEIRA NETO, F. J., BEIER, S. L., CORRENTE, J. E. and PEDROSO, C. E. B. P. (2009), Comparison of the cardio-respiratory effects of methadone and morphine in conscious dogs. Journal of Veterinary Pharmacology and Therapeutics, 32: 317–328. doi: 10.1111/j.1365-2885.2008.01042.x
- Issue published online: 8 JUL 2009
- Article first published online: 4 DEC 2008
- (Paper received 25 January 2008; accepted for publication 29 August 2008)
The effects of methadone and morphine were compared in conscious dogs. Six animals received morphine sulfate (1 mg/kg) or methadone hydrochloride (0.5 mg/kg [MET0.5] or 1.0 mg/kg [MET1.0]) intravenously (i.v.) in a randomized complete block design. Cardiopulmonary variables were recorded before (baseline), and for 120 min after drug administration. One outlier was not included in the statistical analysis for hemodynamic data. Morphine decreased heart rate (HR) compared to baseline from 30 to 120 min (−15% to −26%), while cardiac index (CI) was reduced only at 120 min (−19%). Greater and more prolonged reductions in HR (−32% to −46%) and in CI (−24% to −52%) were observed after MET1.0, while intermediate reductions were recorded after MET0.5 (−19 to −28% for HR and −17% to −27% for CI). The systemic vascular resistance index (SVRI) was increased after methadone; MET1.0 produced higher SVRI values than MET0.5 (maximum increases: 57% and 165% for MET0.5 and MET1.0, respectively). Compared to morphine, oxygen partial pressure (PaO2) was lower (−12% to −13%) at 5 min of methadone (0.5 and 1.0 mg/kg), while carbon dioxide partial pressure (PaCO2) did not change significantly. It was concluded that methadone induces cardiovascular changes that are dose-related and is a more potent cardiovascular depressant agent than morphine in conscious dogs.