Full Opioid Mu Receptor Agonists

morphine

- prototypical analgesic

- onset 5-15min, lasts several hours, epidurals

- risk of histamine release

hydromorphone

- less histamine release

- used IV in place of morphine

- similar onset and duration

oxymorphone

- similar to hydromorphone

- less emetogenic

- sedation may be more smooth in cats and bebes

methadone

- alternative in pre-anesthetic and analgesic protocols

- less histamine release

- less sedation

- less GI signs

fentanyl

- potent, short acting (onset ~1 min, lasts ~30min)

- suitable for CRI

- patch

remifentanil

- similar to fentanyl, more potent

- shortest acting of all agonists (half life 2-5min)

- mainly used as CRI