The influence of anaesthetic technique on metabolism of oral morphine.
The pharmacokinetics of oral controlled release morphine were studied in 10 patients to investigate the effect of two different anaesthetic techniques on its absorption and metabolism. Five patients received general anaesthesia with neuromuscular blockade; the remainder received lumbar epidural analgesia with general anaesthesia but without neuromuscular blocking agents. Blood samples were collected throughout the peri-operative period for estimation of plasma morphine concentration using two radio immunoassay techniques, one specific for morphine, the other less specific and crossreacting with morphine glucuronides. Plasma morphine concentrations with the specific method were similar for the two groups of patients but there was a statistically significant difference between the two groups with the less specific method at 30 and 45 minutes after induction of anaesthesia. This difference was because of the varying concentrations of morphine metabolites and may reflect the change in splanchnic blood flow produced by lumbar epidural analgesia.
Shelly
M P
MP
Department of Anaesthesia, Addenbrooke's Hospital, Cambridge.
Taylor
B L
BL
Quinn
K G
KG
Park
G R
GR
D000284:Administration, Oral; D000328:Adult; D000767:Anesthesia, Epidural; D000768:Anesthesia, General; D003692:Delayed-Action Preparations; D006801:Humans; D009020:Morphine / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*
D003692:Delayed-Action Preparations; D009020:Morphine