Measured Context-sensitive Half-times of Remifentanil and Alfentanil

TLDR

The context‑sensitive half‑time, derived from pharmacokinetic modelling, is proposed as a more clinically relevant measure of drug concentration decline after a constant infusion than the terminal elimination half‑life. The study aimed to determine whether the modelled context‑sensitive half‑time accurately predicts the true time for a 50 % decrease in drug concentration or effect. For a 3‑hour infusion, the modelled context‑sensitive half‑time was 50–55 min for alfentanil and 3 min for remifentanil, while their terminal elimination half‑lives were 111 min and 12–30 min, respectively.

Abstract

Abstract Background The context-sensitive half-time, rather than the terminal elimination half-life, has been proposed as a more clinically relevant measure of decreasing drug concentration after a constant infusion of a given duration. The context-sensitive half-time is derived from computer modelling using known pharmacokinetic parameters. The modelled context-sensitive half-time for a 3-h infusion of alfentanil is 50–55 min and is 3 min for remifentanil. The terminal elimination half-life is 111 min for alfentanil and 12–30 min for remifentanil. It has not been tested whether the modelled context-sensitive half-time reflects the true time for a 50% decrease in drug concentration or drug effect.