[Pharmacology of morphine and its derivatives (review)]

Morphine, the principal alkaloid of "papaver somniferum" is the reference substance of central analgesics, the parmacodynamic constants of which are: analgesia and the possibility of addiction. Respiratory depression is, for many of them, a grave side-effect. At the present time, no substance in this category is fully satisfactory and all may result in dependence. Equi-analgesic doses of dextromoramide, phenoperidine and Fentanyl are less than those of morphine, whilst those of pethidine and pentazocine are higher. Study of the pharmacokinetics of these various substances indicates no common elements, and it is difficult to consider that the analgesic action is proportional to blood levels. Clinical assessment of the mean duration of action makes it possible to divide morphine derivatives into substances with a very short action (20 to 45 minutes) such as Febtanyl and phenoperidine, and those with a longer action (1 to 4 hours) which includes the majority of the other substances. The analgesic activity of Methoadone lasts for 4 to 6 hours. Morphine antagonists such as Methadone, nalophine, naloxone and naltrexone possess specific problems in terms of their utilization. Pharmacological data concerning theses substances are described.