Some pharmacological aspects of drug dependence

The self-administration of drugs to achieve altered states of consciousness is recognized as normal human behaviour. Community attitudes towards drug use vary according to the drug and often bear little relationship to the known pharmacological and toxicological effects of the drug. For an objective assessment of the potential dangers associated with drug use, a distinction is made between drug use and drug abuse. It is stressed that the progression from drug use to drug abuse involves social and psychological factors in addition to the pharmacological factors which are outlined in this paper. The sequential development of drug dependency is described under the headings: Induction; continued consumption; compulsive consumption; withdrawal; abstinence; reinduction. Man uses psychotropic drugs because he finds the effects rewarding. Some experimental models to explore the neurophysiological basis of the reward are described. Experiments employing inhibitors of protein synthesis suggest that the phenomena of tolerance and physical dependence involve the synthesis of new protein. It has been suggested that the new protein might be new receptor molecules for the drug or neurotransmitter substances. These new receptors might constitute a "drug memory" and provide a possible explanation for high relapse rate of drug dependent subjects. A pharmacological basis for the methadone maintenance programme of management of narcotic dependent subjects is briefly outlined.