Drug withdrawal is a physiological or behavioural response to reducing or stopping exposure after adaptation to a drug. It differs from simple elimination of the substance: its manifestations reflect the adapted system functioning under changed exposure. It also differs from recurrence of the original condition, although both can occur together. [ref]
FDA requiring Boxed Warning updated to improve safe use of benzodiazepine drug class. 2020 safety communication, physical dependence and withdrawal definitions
For example, a system that has compensated for a persistent inhibitory influence may show excessive activity when that influence is removed. The timescale of adaptation can differ from the drug elimination timescale, so a response can continue after concentrations have fallen. Physical dependence, drug tolerance and compulsive use describe different phenomena; the presence of one alone does not establish all the others.
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