What is context-sensitive half-time?

What is context-sensitive half-time?

• A. The time needed for the blood concentration of a drug to decrease by 50% after discontinuing a continuous infusion.
• B. The time required for a drug to reach peak concentration after starting an infusion.
• C. The time needed for a drug to be completely eliminated after stopping an infusion.
• D. The time it takes for a drug to begin exerting its effect after administration.

Answer: (A)

Context-sensitive half-time is the time required for the plasma concentration of a drug to fall by 50% after stopping a continuous infusion, and this time depends on how long the infusion has been running. The longer the infusion, the more the drug has redistributed into deep tissue compartments, so the decline after stopping becomes slower. This concept matters for predicting recovery from anesthesia or sedation, since a longer infusion can mean a longer time to wake up even if the drug is stopped. The other ideas describe different concepts—time to reach peak concentration during infusion, complete elimination after stopping (which isn’t a finite instant), or onset of effect after administration—none of which define context-sensitive half-time.

Context-sensitive half-time is the time required for the plasma concentration of a drug to fall by 50% after stopping a continuous infusion, and this time depends on how long the infusion has been running. The longer the infusion, the more the drug has redistributed into deep tissue compartments, so the decline after stopping becomes slower. This concept matters for predicting recovery from anesthesia or sedation, since a longer infusion can mean a longer time to wake up even if the drug is stopped. The other ideas describe different concepts—time to reach peak concentration during infusion, complete elimination after stopping (which isn’t a finite instant), or onset of effect after administration—none of which define context-sensitive half-time.