Morphine-6-glucuronide

[SH4:p102]

• One of the metabolites of morphine

Pharmacokinetics

• Duration of M6G is longer than morphine
  * [???]
• M6G has low permeability of BBB
• M6G has no effect when administered as a single IV dose
  * Some effect when given as infusion

NB:

• M6G is stronger MOP agonist than morphine, with similar duration of action
  * [RDM6:p402]
• Analgesic potency of M6G is 650 times that of morphine, but affinity to MOP is similar
  * [SH4:p102]

Pharmacodynamics

• Morphine and M6G has similar affinity to MOP
• Analgesic potency of M6G is 650-fold higher than morphine
• Possible that majority of morphine's analgesic action is due to M6G

Administration

• Intrathecal M6G has similar analgesic effect as morphine