ABSTRACT
This chapter reviews the present status of our knowledge on the biological disposition and metabolism of narcotic agonists and antagonists, barbiturates, some nonbarbiturate sedative-hypnotics, tranquilizers, and ethanol. Morphine was first isolated by Sertürner in 1803. It constitutes approximately 8 to 12% by weight of opium depending on the geographical source. The analgesic efficiency was found to be a good approximation for the “receptor-activities.” The evidence underscored the importance of lipophilicity and passive penetration of the drugs through the blood-brain barrier. The biotransformation of morphine to normorphine in vitro and in vivo in the rat has also been shown to occur in the brain of rats. Codeine is prepared from morphine by methylation. It is present in opium from 0.7 to 2.5% depending on geographical source. Dihydromorphine is prepared by the catalytic hydrogenation of morphine. The pattern of absorption, metabolism and excretion of dihydromorphine is very similar to that of morphine.
