Clinical Connections Practice Test

Rapid loss of drug effect after repeated exposure is tachyphylaxis. With repeated dosing, the body's response diminishes quickly, even when the same dose is given. This happens because the system adapts—receptors may desensitize or signaling pathways may become less responsive, and sometimes mediators are depleted—so the drug’s effect weakens faster than expected.

Why the other patterns don’t fit: a slower onset implies a delay in when the drug begins to act rather than a reduced magnitude of effect; a total loss after a single dose is an immediate nonresponse, not a rapid decline with repeated use; and a heightened response after repeated dosing is sensitization, the opposite of tachyphylaxis.