Clin Surg | Volume 7, Issue 1 | Research Article | Open Access

The Effects of Premedication with Methadone on Intraocular Pressure in Dogs and Cats

Esmeralda Delgado1*, André Silva2 and Mariana Nunes3

1Centre for Interdisciplinary Research in Animal Health, University of Lisbon, Portugal
2Nova School of Business and Administration, Nova University, Portugal
3Depatment of Veterinary Medicine, University of Lisbon, Portugal

*Correspondance to: Esmeralda Delgado 

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Background: The effects of premedication agents on the ocular physiology should be thoroughly understood by the ophthalmic surgeon so that Intraocular Pressure (IOP) values are kept stable. The purpose of this study was to determine the effects of methadone as a solo-agent of anesthetic premedication on IOP in healthy dogs and cats. The study group included 60 clinically healthy patients, 40 dogs and 20 cats. Ophthalmological examination, including baseline IOP (T0) of the subjects, was performed before methadone administration at a dosage of 0.2 mg kg-1. IOP variations were registered fifteen (T15) and thirty (T30) minutes later. IOP values were compared at each specific time point (T0, T15 and T30) using a repeated-measures Analysis of Variance (ANOVA) and differences were considered significant when P<0.05. Results: The mean ± SD baseline (T0) and post-treatment (T15, T30) IOP values were, respectively, 16.8 ± 3.84 mmHg, 17.6 ± 3.01 mmHg and 16.1 ± 3.28 mmHg for dogs and 17.1 ± 3.31 mmHg, 16.6 ± 3.40 mmHg and 16.61 ± 2.81 for cats. There were no statistically significant differences between baseline and post-treatment values in dogs (p=0.107) or cats (p=0.077). The sedative effect of methadone did not affect the ocular globe or nictitating membrane position nor the menace response, dazzle reflex, corneal blink reflex or palpebral reflexes in any case. None of the animals studied presented with the secondary effects associated with opioids such as salivation, nausea, vomit, defecation, dysphoria or a clear modification of the respiratory pattern. Conclusion: The administration of methadone as a solo-agent of anesthetic premedication at a dosage of 0.2 mg kg-1 did not cause significant changes on IOP values in dogs or cats. Methadone presented as a safe alternative for sedation, anesthetic premedication or analgesia in ophthalmological patients since it did not interfere with IOP regulation.


Delgado E, Silva A, Nunes M. The Effects of Premedication with Methadone on Intraocular Pressure in Dogs and Cats. Clin Surg. 2022; 7: 3557..

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