abstinence syndrome

a constellation of physiologic changes undergone by persons or animals who have become physically dependent on a drug or chemical due to prolonged use at elevated doses, but who are abruptly deprived of that substance. The abstinence syndrome varies with the drug to which dependence has developed. Generally the effects observed are in an opposite direction from those produced by the drug; e.g., the withdrawal syndrome from central nervous system depressants such as barbiturates and benzodiazepines consists of insomnia, restlessness, tremulousness, hallucinations, and, in the extreme, tonic-clonic convulsions which may prove fatal. The onset time and severity of the abstinence syndrome depend upon how rapidly the drug disappears from the body.