Effects of tepoxalin and medetomidine on glomerular filtration rate in dogs

The objective of this study was to evaluate glomerular filtration rate (GFR) and the cardiovascular effects of the combination of tepoxalin (TPX) and medetomidine (MED) in dogs. Six healthy dogs of either sex (5 males and 1 female), aged 2.5 ± 2.2 years and weighing 14.7 ± 4.4 kg, were studied. Each dog received four randomized treatments with a minimum of 1 week between treatments: no medication as the control group (C); MED (750 μg/m², intravenously [IV]); TPX (10 mg/kg orally for 3 days); and MT (TPX 10 mg/kg orally for 3 days plus MED 750 μg/m², IV). Iohexol (300 mg iodine/kg, IV) was injected in all dogs in each treatment as an indicator of GFR. Blood samples for serum iohexol clearance analysis were collected before and 1, 2, 5, 10, 15, 20, 60, 120, 240 and 360 min after the iohexol administration. Rectal temperature, heart rate, respiratory rate and direct arterial pressure (AP) were obtained before and 5, 10, 15, 20, 60, 120, 240 and 360 min after the iohexol injection. GFR did not differ between treatments. Heart rate was significantly lower in the MED and MT groups than in C or TPX. Mean AP was significantly higher with MT than TPX, but only at 5 min after the iohexol injection. TPX, MED and the combination of these two drugs do not alter GFR. The combination has minimal effect on cardiovascular variables at these doses in healthy dogs.