clinical pharmacology

NARCOTIC ANALGESICS AND GASTRIC EMPTYING

Previous studies in women during labour have suggested that narcotic analgesic administration results in a marked reduction in the rate of absorption of oral paracetamol. A recent study in 8 healthy male volunteers confirms that this reduction is due to inhibition of gastric emptying by the narcotic analgesics.

Subjects were given oral paracetamol (20mg/kg), alone or 30 minutes following intramuscular pethidine (lSOmg) or diamorphine (I Omg). Both narcotic analgesics significantly reduced the peak level of paiacetamol in plasma and increased the gastric emptying time. Times for 50% emptying rose from the control valu~ of 11.9 minutes to 89.5 minutes (pethidine) and to greater than 120 minutes (diamorphine). Corresponding plasma levels of paracetamol were 20, 13.8, and 5.21Jg/ml, reached after 22, 114, and 142 minutes respectively.

'Narcotic analgesics are widely used in all branches of medical practice. Because of their major inhibitory effect on gastric emptying they are likely to influence the absorption of most if not all orally administered drugs. This may represent one of the most important clinical drug absorption interactions.'

Nimmo, W.S. et al.: British Journal of Clinical Pharmacology 2: 509 (Dec 1975)

INPHARMA 10th January, 1976 p13