Morphine
Morphine, an alkaloid. Prototype µ-opioid agonist. Also binds κ and δ opioid receptors with lower affinity. Analgesia is µ-mediated; respiratory… Oral half-life 2.5 h.
Prototype µ-opioid agonist. Also binds κ and δ opioid receptors with lower affinity. Analgesia is µ-mediated; respiratory depression, euphoria, miosis, and GI hypomotility are µ effects. Metabolised primarily by UGT2B7 → morphine-6-glucuronide (active, potent analgesic) and morphine-3-glucuronide (not analgesic, neuroexcitatory — accumulates in renal failure).
Pharmacokinetics
- Oral — t½ 2.5 h · F 24% · Vd 231 L
- IV — t½ 2.5 h · F 100% · Vd 231 L
- Intramuscular — t½ 2.5 h · F 100% · ka 11.59 h⁻¹ · Vd 231 L
- Subcutaneous — t½ 2.5 h · F 100% · ka 16.66 h⁻¹ · Vd 231 L
- Intranasal — t½ 2.5 h · F 10% · ka 27.27 h⁻¹ · Vd 231 L
Related compounds
- Alprazolam — major
- Mirtazapine — caution
Sources: PMID:11510626, PMID:26143953, PMID:9686407, PMID:8249052