- synthetic opioid of the aminocyclohexanol group
MECHANISM OF ACTION
- opioid receptor agonist + more!
- centrally acting:
(1) moderate affinity for mu receptors, weak kappa & delta.
(2) in spinal descending inhibitory pathways by inhibition of neuronal reuptake of norephinephrine & serotonin.
(3) also via presynaptic stimulation of serotonin release.
- racemic mixture of two enantiomers
- PO: 50-150mg
- IV: 50mg/mL
- 1-3mg/kg loading dose -> 50-100mg Q6 hrly
- 10 x less potent than morphine
- analgesia + shivering
- nausea on fast injection
- Absorption – bioavailability = 90%
- Distribution – Vd 4L/kg, protein binding = 20%
- Metabolism – hepatic, one active metabolite
- Elimination – urinary, t1/2 = 6 hrs