Age-related morphine kinetics

Abstract

The kinetic disposition of morphine [an analgesic] was compared in 13 young and 7 older healthy subjects after a single i.v. dose of 10 mg/70 kg morphine. The apparent volume of distribution at steady-state in elderly subjects was only 1/2 of that in young subjects. This difference was derived from reductions in both central and peripheral kinetic compartment volumes in the older subjects. The .beta. elimination phase for morphine was more rapid, but its plasma clearance was reduced in older subjects. Calculation of the peripheral compartment morphine concentration for these subjects indicated that drug concentration in this kintic space was higher in older subjects for 1.5 h after dosing.