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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 ...
Tolerability refers to the degree to which overt adverse effects of a drug can be tolerated by a patient. [1] Tolerability of a particular drug can be discussed in a general sense, or it can be a quantifiable measurement as part of a clinical study.
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 ...
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.
TDM interpretation: an anticancer drug is given to a patient at a dosage of 400 mg every day at 8:00 am. A TDM sample is obtained at 6:00 am, showing a drug concentration of 0.46 mg/L. 1) Regarding “normality”, the result is around the 25th percentile, suggesting a rather high drug clearance in this patient.
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 .
The ED50 is commonly used as a measure of the reasonable expectancy of a drug effect, but does not necessarily represent the dose that a clinician might use. This depends on the need for the effect, and also the toxicity. The toxicity and even the lethality of a drug can be quantified by the TD 50 and LD 50 respectively. Ideally, the effective ...