Measured Context-sensitive Half-times of Remifentanil and Alfentanil

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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.