Efeitos do tramadol sobre os parâmetros oftálmicos em cães

Abstract

Tramadol has been used as an analgesic for dogs and cats. Its clinical importance is because it has a few adverse effects, oral presentation and a long duration compared to conventional opioids. Tramadol is an atypical opioid, acting as a weak agonist for μ receptors and inhibiting serotonin and noradrenaline reuptake. The hypothesis that this drug does not alter ophthalmic parameters, such as intraocular pressure, pupillary diameter and tear production, stimulates its use as a preoperative analgesic in intraocular surgeries and in the control of pain from any etiology in patients with ophthalmopathy. This study aimed to evaluate the effects of tramadol on tear production, intraocular pressure (IOP) and pupil diameter (PD) in healthy dogs (article 1) and in dogs with keratoconjunctivitis sicca or with facolytic uveitis (article 2). In healthy dogs, the effect of tramadol was compared in two different doses (4mg/kg and 6mg/kg) and in dogs with ophthalmopathy, only with 4mg/kg. The tear production (Schirmer's tear test, TLS-1), IOP (aplanation tonometry) and PD (electronic pachymetry) were measured before, 30 and 60 min in healthy dogs, and before, 60 and 120 min in dogs with ophthalmopathy, after intramuscular injection of tramadol. The data obtained were evaluated by the analysis of variance for repeated measurements (P<0.05). There was no significant difference between the times and doses studied for any variables in healthy dogs and in those with keratoconjunctivitis sicca. But in the dogs with facolytic uveitis, there was a significant difference in pupil diameter at 120 min of evaluation (P=0.02). Under the conditions of this study, tramadol did not alter the tear production and IOP of healthy dogs and with severe keratoconjunctivitis sicca. Although it does not change the PD of healthy dogs, it should be used with caution in patients with facolytic uveitis, due to miosis.