A pharmacological classification of drugs of abuse

This paper questions the validity of the distinction between "psychic" and "physical" dependence in relation to drug addiction. The author describes the action of dependence-producing or addictive drugs on the brain at the neuronal and structural level as well as the alterations of arousal, awareness, impairment of sleep, memory, psychomotor performance and sensory perception which are symptomatic of neuropsychological toxicity. Addictive drugs are consumed for the primary pleasurable reward that they produce as a result of their effects on the pleasure reward mechanisms of the brain. These pleasurable sensations will act as reinforcers for repeated administration when the drug effects have worn off and induce a compulsive drug-oriented behaviour. The tolerance, which develops to addictive drugs and the occurrence of withdrawal symptoms, are added reinforcers. The author therefore proposes a pharmacological classification of the most commonly used addictive drugs based on these foregoing effects which may be quantified to a large extent.