| Class | Opioid |
|---|---|
| Chemistry |
Natural phenanthrene |
| Routes of administration |
Oral, IV |
| Absorption |
Well absorbed orally, 50% bioavailability |
| Solubility |
pKa 8.21, relatively hydrophilic |
| Distribution |
VOD = 3-6L/kg; 7-25% protein-bound |
| Metabolism |
Hepatic metabolism; notable metabolites include morphine |
| Elimination |
Minimal unchanged drug cleared renally, but most of the metabolites rely on renal excretion |
| Time course of action |
Half-life 2-3 hours |
| Target receptor |
mu-opiate receptor (pre-synaptic G-protein coupled receptor) |
| Mechanism of action |
Hyperpolarisation of cell membrane by increasing potassium conductance; reduced production of cAMP and closure of voltage-gated calcium channels |
| Clinical effects |
Analgesia, respiratory depression, constipation, miosis, urinary retention. |
| Literature reference |
Crow et al (2021) |
| CICM details of understanding | Not specifically listed in the CICM syllabus |
| Mentioned around Deranged Physiology | |
| Related SAQs |