Editing Drug tolerance (section)

{{Short description|Reduced reaction to a drug following repeated use}}
{{About|human resistance to the effects of drugs|pathogenic resistance to the effects of drugs|Drug resistance}}
{{Addiction glossary}}
'''Drug tolerance''' or '''drug insensitivity''' is a [[Pharmacology|pharmacological]] concept describing subjects' reduced reaction to a drug following its repeated use. Increasing its dosage may re-amplify the drug's effects; however, this may accelerate tolerance, further reducing the drug's effects. Drug tolerance is indicative of drug use but is not necessarily associated with [[drug dependence]] or [[addiction]].<ref>{{Cite journal|title=The relationship of addiction, tolerance, and dependence to alcohol and drugs: a neurochemical approach. | pmid=3325655 | volume=4 | issue=3–4 | journal=J Subst Abuse Treat | pages=197–207 | last1 = Miller | first1 = NS | last2 = Dackis | first2 = CA | last3 = Gold | first3 = MS | doi=10.1016/s0740-5472(87)80014-4| year=1987 }}</ref> The process of tolerance development is reversible (e.g., through a [[drug holiday]]<ref>{{Cite journal|title=Drug holiday and management of Parkinson disease. | pmid=7192805 | volume=30 | issue=12 | journal=Neurology | pages=1257–61 | last1 = Weiner | first1 = WJ | last2 = Koller | first2 = WC | last3 = Perlik | first3 = S | last4 = Nausieda | first4 = PA | last5 = Klawans | first5 = HL | doi=10.1212/wnl.30.12.1257| year=1980 | s2cid=23029500 }}</ref>) and can involve both [[physiological]] factors and [[psychological]] factors.<ref>{{Cite book|doi=10.1007/978-3-540-38918-7_140|title = Encyclopedia of Molecular Pharmacology|pages=1203–1207|year = 2008|last1 = Schöneberg|first1 = Torsten|isbn=978-3-540-38916-3|chapter=Tolerance and Desensitization}}</ref>

One may also develop drug tolerance to [[side effect]]s,<ref>{{Cite journal|title=Side-effect 'tolerance' in elderly long-term recipients of benzodiazepine hypnotics. | pmid=6440434 | volume=13 | issue=6 | journal=Age Ageing | pages=335–43 | last1 = Swift | first1 = CG | last2 = Swift | first2 = MR | last3 = Hamley | first3 = J | last4 = Stevenson | first4 = IH | last5 = Crooks | first5 = J | doi=10.1093/ageing/13.6.335| year=1984 | doi-access = free }}</ref> in which case tolerance is a desirable characteristic. A medical intervention that has an objective to increase tolerance (e.g., [[allergen immunotherapy]], in which one is exposed to larger and larger amounts of [[allergen]] to decrease one's [[allergic reactions]]) is called [[Desensitization (medicine)|drug desensitization]].<ref>{{Cite web|url=http://www.jiaci.org/issues/vol24issue2/1.pdf|title=Rapid Drug Desensitization for Hypersensitivity Reactions to Chemotherapy and Monoclonal Antibodies in the 21st Century}}</ref>

The opposite concept to drug tolerance is [[reverse tolerance]], 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.<ref>{{Cite web|url=http://hams.cc/reverse/|title=What Is Reverse Tolerance?}}</ref>

Drug tolerance should not be confused with [[drug tolerability]], which refers to the degree to which overt [[adverse effect]]s of a drug can be tolerated by a patient.