Tachyphylaxis is defined as which of the following?

Tachyphylaxis is defined as which of the following?

• A. Rapid desensitization or loss of receptor's response
• B. Gradual development of tolerance over weeks
• C. Increased receptor sensitivity
• D. Reversible up-regulation

Answer: (A)

Tachyphylaxis means a rapid drop in the effect of a drug after initial exposure due to quick desensitization of the receptor (or rapid depletion of the signaling mechanism). That’s why the statement describing rapid desensitization or loss of the receptor’s response best fits this concept. Receptors can become less responsive quickly through processes like receptor phosphorylation and arrestin-mediated desensitization, or by depleting mediators at the site, so the same dose produces a smaller or no effect. The other ideas describe different phenomena: tolerance develops more slowly over days to weeks; increased receptor sensitivity would heighten the response rather than diminish it; and reversible up-regulation would also increase responsiveness, not reduce it.

Tachyphylaxis means a rapid drop in the effect of a drug after initial exposure due to quick desensitization of the receptor (or rapid depletion of the signaling mechanism). That’s why the statement describing rapid desensitization or loss of the receptor’s response best fits this concept. Receptors can become less responsive quickly through processes like receptor phosphorylation and arrestin-mediated desensitization, or by depleting mediators at the site, so the same dose produces a smaller or no effect.

The other ideas describe different phenomena: tolerance develops more slowly over days to weeks; increased receptor sensitivity would heighten the response rather than diminish it; and reversible up-regulation would also increase responsiveness, not reduce it.