PLASMA CONCENTRATION OF MORPHINE AFTER I.M., EXTRADURAL AND INTRATHECAL ADMINISTRATION

Abstract

Seventeen patients received morphine 0.2 mgkg^-1 in a 10% dextrose solution i.m. (n = 5), extradurally (n = 6) and intrathecally (n = 6) for pain after operation. Morphine was measured in plasma by radioimmunoassay. Plasma immunoreactive morphine concentration was significantly less after intrathecal administration than after intrathecal administration than after i jn. and extradural administration(P<0.05) at 2, 10, 15 and 30 min. We conclude that morphine given extradurally has a greater initial rate of vascular absorption than morphine given intrathecally and is similar to that observed after i.m. administration.