tachyphylaxis

Rapid appearance of progressive decrease in response to a given dose following repetitive administration of a pharmacologically or physiologically active substance. [tachy- + G. phylaxis, protection]

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tachy·phy·lax·is .tak-i-fi-'lak-səs n, pl -lax·es -.sēz diminished response to later increments in a sequence of applications of a physiologically active substance (as the diminished pressor response that follows repeated injections of renin)

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n.

a falling-off in the effects produced by a drug during continuous use or constantly repeated administration, common in drugs that act on the nervous system.

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tachy·phy·lax·is (tak″e-fə-lakґsis) [tachy + phylaxis] 1. rapid immunization against the effect of toxic doses of an extract or serum by previous injection of small doses. 2. rapidly decreasing response to a drug or physiologically active agent after administration of a few doses.