Opioids for small animals

OPIOIDS FOR SMALL ANIMALS

MORPHINE (mu agonist)

Use: moderate/severe pain
Higher dose: good sedation
– Causes vomiting
– Risk of histamine reaction if given IV
– time to effect: 20-30 minutes
– duration of effect: 2-4 hours
– dose: 0.1-1.0 mg/kg IM

METHADONE (mu agonist)

Use: moderate/severe pain
Not so good sedation if used alone
No vomiting
– time to effect: 20-30 minutes
– duration of effect: 2-4 hours
– dose: 0.1-1.0 mg/kg IM

PETHIDINE (mu agonist)

Use: moderate/severe pain
Questionable sedation if used alone
– Risk of histamine reaction if given IV
– time to effect: 15-20 minutes
– duration of effect: 1 hour
– dose: 1-5 mg/kg IM

FENTANYL (mu agonist)

Good sedation with high doses
– time to effect: 5 minutes IV
– duration of effect: up to 15 minutes IV
– dose IV: 2-10 mcg/kg (when awake) 1-2 mcg/kg (anesthetized), 2-10 mcg/kg/hour (infusion)

BUTORPHANOL (agonist/antagonist)

– use: mild/moderate pain
– good sedation with high doses
– time to effect: 10-15 minutes (IM)
– duration of effect: 1-2 hours (IM)
– dose: 0.1-0.4 mg/kg IM

BUPRENORPHINE (partial agonist)

– use: mild/moderate pain
– may be used as effective sedation in cats
– time to effect: 45-60 minutes
– duration of effect: 4-8 hours (increasing the dose will increase the duration)
– dose: 0.02-0.05 mg/kg IM