opioid might facilitate management during the immediate postanesthetic and postoperative period.

Azaperone (Stresnil® and droperidol.

Azaperone is approved for swine, in which it is used mainly to prevent fighting and as a preanesthetic agent. It is a more potent sedative and less hypotensive than the phenothiazines, but has no analgesic effect (Flecknell, 1987). Droperidol is incorporated with fentanyl in Innovar-Vet® (see Chapter 5).

Like the phenothiazines, butyrophenones exert general sympatholytic activity that probably accounts for many of their common properties. Butyrophenones seem more likely to produce extrapyramidal signs of rigidity, tremors, and catalepsy.

In pigs, azaperone at 2.2 mg/kg intramuscularly produces sedation, but has no analgesic effect. Combined at 5 mg/kg with metomidate (10 mg/kg) intramuscularly, it produces sedation and analgesia suitable for minor surgical procedures (Flecknell, 1987). In horses, azaperone administered intravenously at 0.22–0.44 mg/kg might cause excitement and extrapyramidal effects and is not recommended (Muir et al., 1989).

Diazepam (Valium®), zolazepam, and midazolam (Versed®).

Benzodiazepines induce a mild calming effect and have therapeutically useful anticonvulsant, muscle-relaxant, and hypnotic effects in animals; they have no analgesic activity. They are commonly used with analgesic drugs (e.g., xylazine, opioids, or ketamine) to enhance muscle relaxation.