Drug tolerance

Drug tolerance is a reduced response to a drug after repeated exposure. It can cause a previously effective dose to produce a weaker effect.

Pharmacodynamic tolerance: Reduced drug response caused by adaptations in the tissues or signaling systems the drug affects. It develops when repeated exposure changes the response downstream of the drug’s concentration.
Dose–response relationship: The relationship between the amount of a substance and the magnitude of its effect. Tolerance can shift this relationship so a larger dose is needed for the same response.
Opioid tolerance: Reduced responsiveness to opioid drugs after repeated exposure. It can complicate pain treatment and changes how opioid doses affect a person.
Withdrawal: A set of symptoms that can follow stopping or sharply reducing a drug after adaptation to its repeated use. Tolerance may develop alongside dependence, making abrupt dose reduction cause withdrawal.
Pharmacokinetic tolerance: Reduced drug effect caused by changes that lower the concentration reaching its site of action. Repeated exposure can increase drug breakdown or clearance, leaving less drug available.
Drug potency: The amount of a drug required to produce a specified effect. A tolerant body may respond as if the drug were less potent, without changing the drug itself.
Benzodiazepine tolerance: Reduced responsiveness to benzodiazepines after repeated use. Tolerance can diminish some effects of these drugs, including sedation.
Overdose: Harmful effects caused by taking an excessive amount of a drug or other substance. Tolerance to one effect may not protect against overdose from other effects or after tolerance falls.
Receptor desensitization: A decrease in a receptor’s responsiveness after sustained or repeated stimulation. It is one cellular route by which repeated drug exposure weakens an effect.
Drug efficacy: The maximum effect a drug can produce through a particular biological system. Tolerance often reduces responses at ordinary doses but does not necessarily change the drug’s maximum efficacy.

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