Pharmacokinetic Data of Fentanyl, Midazolam and Enflurane as Obtained by a New Method for Arbitary Schemes of Administration

Abstract

The knowledge of the pharmacokinetic profile of a drug is one essential for its rational dosing. Kinetic parameters such as total clearance, volumes of distribution and half life are commonly determined from drug concentrations after single bolus administration. The advantage of this procedure is that pharmacokinetic data can be easily derived from the resultant blood levels. But some disadvantages are associated with this procedure; Firstly, blood levels due to a bolus injection often decay very rapidly. As a consequence, the overall sampling time is limited by the precision of the chemical estimation method, and this may lead to estimation errors in the terminal half-life. Secondly, a single bolus is frequently not the usual way the drug is used to achieve the desired pharmacodynamic effect. This, in turn, often leads to small series for the determination of mean kinetic data. The problem of estimating the pharmacokinetic data from drug concentration and the known administration scheme is commonly referred to as the deconvolution problem. In recent years several methods for special administration schemes have been pub-lished ^(1–5) but little has been worked out for arbitrary administration schemes.