| Class | Opioid antagonist |
|---|---|
| Chemistry |
Phenanthrene |
| Routes of administration |
IV, S/C, IM |
| Absorption |
Poorly absorbed; oral bioavailability <1% |
| Solubility |
pKa = 9.9; practically insoluble in water |
| Distribution |
VOD = 1.1 L/kg; 11-15% protein-bound |
| Metabolism |
About 15% of the dose is metabolised in the liver, into abot 5 metabolites |
| Elimination |
About 85% is eliminated as unchanged drug, 50% via urine and 35% in faeces |
| Time course of action |
Half-life is approximately 8 hours |
| Target receptor |
μ, δ- and κ-opioid receptors in the myoenteric plexus of the intestine |
| Mechanism of action |
Peripherally acting opioid receptor antagonist which does not penetrate the blood-brain barrier; exerts its effect by reversing the sustained increase in smooth muscle tone which results from opioid use |
| Clinical effects |
Relatively free from adverse effects; could develop peripheral syptoms of opioid withdrawal (poerection, tremor, shivering, etc) |
| Literature reference |
FDA data sheet |
| CICM details of understanding | Not specifically listed in the CICM syllabus |
| Mentioned around Deranged Physiology | |
| Related SAQs |