Effect of meloxicam and butorphanol on minimum alveolar concentration of isoflurane in rabbits

Abstract

Objective - To determine the effects of meloxicam and butorphanol on minimum alveolar concentration of isoflurane (MACISO) in rabbits. Animals - 10 healthy young adult female rabbits. Procedure - Rabbits were anesthetized with isoflurane on 3 occasions in a blinded, randomized complete block design to determine the MACISO associated with administration of meloxicam (0, 0.3, or 1.5 mg/kg, PO) and butorphanol (0.4 mg/kg, IV). The MACISO was determined by use of a paw clamp technique as the end-tidal concentration of isoflurane halfway between the values that allowed or inhibited purposeful movement. Rectal temperature, end-tidal CO2 concentration, heart rate, oxygen saturation, and arterial blood pressure were measured to evaluate cardiopulmonary function. Results - Mean ± SE MACISO in saline (0.9 % NaCl) solution-treated rabbits was 2.49 ± 0.07% and was not significantly different from that associated with administration of meloxicam at 0.3 mg/kg (2.56 ± 0.07%) or 1.5 mg/kg (2.66 ± 0.07%). Butorphanol significantly reduced the MACISO to 2.30 ± 0.07% when administered with saline solution alone, 2.27 ± 0.07% when administered with 0.3 mg of meloxicam/kg, and 2.33 ± 0.07% when administered with 1.5 mg of meloxicam/kg. The percentage reduction in MACISO was significantly greater for rabbits that received butorphanol and meloxicam at either dose, compared with butorphanol and saline solution. Conclusions and clinical relevance - Results indicated that meloxicam does not have a direct isoflurane-sparing effect and does not interfere with the anesthetic-sparing effect of butorphanol in rabbits.