Morphine Flashcards
What is the pKa?
8
What amt is protein bound?
35% (mod)
What is the volume of distribution?
3.5L/kg
What is the IV peak effect time
10 mins
What is the issue with orally administered morphine
Becomes ionised in the acidic gastric environment
Absorption is delayed
Bioavailability is reduced to 30% due to extensive hepatic first pass metabolism
What are the respiratory effects
Depression with reduced RR >TV Blunts hypercarbic response Depresses cough reflex Bronchospasm due to histamine release Occ chest wall rigidity
What are the cardiovascular effects
Mild bradycardia and hypotension 2’ to histamine release
Reduced SNS tone dec SVR
What are the CNS effects
Analgesia, sedation, euphoria, dysphoria
What are the endocrine effects
Inhibits release of ACTH, Prolactin, Gonadotrophin
Stimulates ADH -> urinary retention
How is morphine metabolised
Metabolised in gut wall and liver to Morphine-3-glucuronide (70%) - effects arousal state
and Morphine-6-glucuronide (10%) 13x more potent than morphine
Some renal metabolism
Excretion is mainly renal - accumulation in renal failure, 7-10% biliary excretion
What is the half life
160mins
What is the IV dose
0.1-0.2mg/kg q4h titrated to effect
Major side effects
Dependence and addiction, tolerance, respiratory depression (delayed with intrathecal or epidural administration) Pruritis Rash Constipation Nausea/vomiting
