What is tachyphylaxis?

• A. Rapid desensitization or loss of receptor's response
• B. Slow development of tolerance
• C. Increased receptor expression
• D. No change in response

Answer: (A)

Tachyphylaxis is a rapid loss of drug response after repeated exposure, even when the dose and drug levels are unchanged. This is a pharmacodynamic desensitization that happens quickly, as receptors or downstream signaling become less responsive—often through mechanisms like receptor phosphorylation and arrestin-mediated desensitization, receptor internalization, or depletion of mediators needed for the drug’s effect. Because it can occur within minutes to hours, the same dose may produce little or no effect after initial administration. This contrasts with tolerance, which develops more slowly over days and can involve broader changes such as altered drug metabolism or receptor expression. So rapid desensitization or loss of receptor response best captures tachyphylaxis.