PHARMACOKINETICS OF IV AND RECTAL PETHIDINE IN CHILDREN UNDERGOING OPHTHALMIC SURGERY

We have studied the pharmacokinetics of iv. and rectal pethidine in 20 children age 4-8 yr undergoing ophthalmic surgery. After i.v. adminis tration, the clearance of pethidine was mean 10.4 (SD 1.7) ml kg-1 min -1, volume of distribution at steady state 2.8 (0.6) litre kg-1 and el imination haff-life 3.0 (0.5) h. After rectal administration, plasma p ethidine concentrations varied greatly and peak concentrations appeare d late, at 147 (44) min. The mean systemic bioavailability after recta l administration was approximately 55%. Because the bioavailability of rectal pethidine varies greatly, this route is not encouraged in the management of acute pain.