Table 1.

Details of opioid drugs in common use in dogs and cats

Drug	Analgesic efficacy	Dose and route	Duration of action	Major drawbacks
Morphine	Excellent	0.1-0.2 mg/kg IM	Up to 4 hours	May cause vomiting
Pethidine	Good	3-5 mg/kg IM	Up to 2 hours	Histamine release if administered IV
Buprenorphine	Moderate - good	10-20 μg/kg IM	Up to 6 hours	May prevent action of morphine
Butorphanol	Poor	0.2-0.4 mg/kg IM	Up to 1.5 hours	Weak analgesic