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Drug tolerance or drug insensitivity is a 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.
For example, a patient could possess a genetic defect in a drug metabolizing enzyme in the cytochrome P450 superfamily. While most individuals will possess the effective metabolizing machinery, a person with a defect will have a difficult time trying to clear the drug from their system. Thus, the drug will accumulate within the blood to higher ...
Tachyphylaxis (Greek ταχύς, tachys, "rapid", and φύλαξις, phylaxis, "protection") is a medical term describing an acute, sudden decrease in response to a drug after its administration (i.e., a rapid and short-term onset of drug tolerance). [1] It can occur after an initial dose or after a series of small doses.
Drug, toxin, or chemical resistance is a consequence of evolution and is a response to pressures imposed on any living organism. Individual organisms vary in their sensitivity to the drug used and some with greater fitness may be capable of surviving drug treatment.
First, desensitization may be equivalent to drug tolerance and refers to subjects' reactions (positive or negative) to a drug reducing following its repeated use. This is a macroscopic, organism-level effect and differs from the second meaning of desensitization, which refers to a biochemical effect where individual receptors become less ...
Cross-tolerance is a phenomenon that occurs when tolerance to the effects of a certain drug produces tolerance to another drug. It often happens between two drugs with similar functions or effects—for example, acting on the same cell receptor or affecting the transmission of certain neurotransmitters .
Tolerability, however, is often relative to the severity of the medical condition a drug is designed to treat. [1] For instance, cancer patients may tolerate significant pain or discomfort during a chemotherapeutic study with the hope of prolonging survival or finding a cure, whereas patients experiencing a benign condition, such as a headache ...
Drug tolerance or physiological tolerance, a decrease in the response to a substance due to previous exposure Alcohol tolerance; Multidrug tolerance or antibiotic tolerance, the ability of a disease-causing microorganism to resist killing by antimicrobials; Immune tolerance or immunological tolerance, by which the immune system does not attack ...