Reverse tolerance

Reverse tolerance or drug sensitization is a pharmacological concept describing subjects' increased reaction (positive or negative) to a drug following its repeated use. Not all drugs are subject to reverse tolerance.

This is the opposite concept to drug tolerance (or drug desensitization), in which case the subject's reaction or effect will increase following its repeated use. The two notions are not incompatible and tolerance may sometimes lead to reverse tolerance. For example, heavy drinkers initially develop tolerance to alcohol (requiring them to drink larger amounts to achieve a similar effect) but excessive drinking can cause liver damage, which then puts them at risk of intoxication when drinking even very small amounts of alcohol.

In some cases, drug sensitization may also refer to medical interventions (e.g., a drug holiday) that have for objective to reduce the insensitivity caused after drug tolerance has been established.

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