Effects of perzinfotel on the minimum alveolar concentration of isoflurane in dogs when administered as a preanesthetic via various routes or in combination with butorphanol

To determine the anesthetic-sparing effects of perzinfotel when administered as a preanesthetic via IV, IM, or SC routes or IM in combination with butorphanol. 6 healthy sexually intact Beagles (4 males and 2 females; age, 18.5 to 31 months; body weight, 9.8 to 12.4 kg). After administration of a placebo, perzinfotel (10 to 30 mg/kg), or a perzinfotel-butorphanol combination, anesthesia was induced in dogs with propofol and maintained with isoflurane in oxygen. The following variables were continuously monitored: bispectral index; heart rate; systolic, diastolic, and mean arterial blood pressures; end-tidal concentration of isoflurane; end-tidal partial pressure of CO(2); oxygen saturation as measured by pulse oximetry; rectal temperature; and inspiration and expiration concentrations of isoflurane. A noxious stimulation protocol was used, and the minimum alveolar concentration (MAC) was determined twice during anesthesia. IV, IM, and SC administration of perzinfotel alone decreased the mean isoflurane MAC values by 32% to 44% and significantly increased bispectral index values. A dose of 30 mg of perzinfotel/kg IM resulted in significant increases in heart rate and diastolic arterial blood pressure. The greatest MAC reduction (59%) was obtained with a combination of 20 mg of perzinfotel/kg IM and 0.2 mg of butorphanol/kg IM, whereas administration of butorphanol alone yielded a 15% reduction in the isoflurane MAC. SC, IM, or IV administration of perzinfotel prior to induction of isoflurane anesthesia improved anesthetic safety by reducing inhalant anesthetic requirements in healthy dogs.