A review of the continuum of drug-induced states of excitation and depression

Abstract

Simplistic concepts which label a drug as an anesthetic, excitant, hallucinogen, convulsant, anticonvulsant, etc., can be extremely misleading. For example, one could label diethyl ether as a stimulant, euphoriant, hallucinogen or anesthetic. Each description partly characterizes ether at some dose/time period but does not describe the totality of drug action. Another example is phenytoin, which is universally considered to be an anticonvulsant agent, but can induce seizures at high doses. Further, the argument that one action is ‘the’ desired effect and other actions are side effects is likewise misleading. The decision as to which is a desired effect and which is side effect depends upon the desired effect. For example, ophthalmologists dilate the pupil of the eye and paralyze accommodation with atropine. They regard the dry mouth and reduced bladder and gastrointestinal tract excitability as side effects. However, the urologist or gastroenterologist uses atropine because of the latter effects and considers the effects on the eyes to be the side effects. A more satisfactory approach to drug classification would be to describe the continuum of total drug actions which occur according to the dose and time course of effects. The advent of the excessive nonmedical use of drugs makes this réévaluation of central nervous system (CNS) acting drug classes critical.