Pharmacokinetics of the Infusion of Alfentanil in Man

Abstract

The pharmacokinetics of alfentanil under the conditions of an empirically derived 1-h continuous infusion of 3 micrograms kg-1 min-1, with a bolus of 80 micrograms kg-1, both i.v., were determined in five patients. The distribution half-life (mean +/- SD) (7.4 +/- 3.1 min), elimination half-life (86.7 +/- 15.8 min), apparent volume of distribution, Varea (0.44 +/- 0.15 litre kg-1) and elimination clearance (3.33 +/- 0.75 ml kg-1 min-1) were similar to those previously reported for a single bolus of alfentanil. These values for apparent volume of distribution and clearance can be used to calculate correct bolus and infusion doses to maintain any desired steady state plasma concentration using standard formulae: for example, to maintain a steady state plasma concentration of 400 ng ml-1, a bolus dose of 176 micrograms kg-1 and an infusion of 1.3 micrograms kg-1 min1 would be required.

Pharmacokinetic parameter sets of alfentanil revisited: optimal parameters for use in target controlled infusion and anaesthesia display systems

“…3). The median MDPE and log bias in the study populations were within or very close to the acceptable limits (+20% or +0.1) with the parameters by Fragen, 15 Scott, 20 and Scott weight adjusted, whereas the others were all significantly different from control (Fig. 3).…”

“…The median MDAPE and log accuracy in both populations was within the limits of acceptance with the parameter sets by Scott, 20 Fragen, 15 and Scott weight adjusted, whereas it was outside with the others (Fig. 2).…”

“…2), the MDAPE and log accuracy of the parameter sets by Scott, 20 Fragen, 15 In the parameter sets by Maitre 18 and Lemmens, 17 the MDAPE was higher when alfentanil was administered as infusion compared with bolus administration; whereas in the log accuracy this difference was significant with the parameters by Lemmens 17 (P,0.003). This was reflected by the multiple pairwise comparisons between the different parameter sets, which yielded different results when alfentanil was administered as multiple boluses or as infusion (as mentioned above).…”

“…2), the MDAPE with the Scott parameters was significantly lower than with the parameters by Hudson, 16 Mertens, 28 Lemmens, 17 and Shafer (P,0.05). MDAPE values were 22.3% (Scott), 20 26.5% (Fragen), 15 26.5% (Scott weight adjusted), and 41% (Maitre). 18 The log accuracy was significantly lower compared with Hudson, 16 Lemmens, 17 and Shafer (P,0.05).…”

“…The parameter set by Fragen 15 was selected as control because MDPE and log bias were optimally within the acceptable range (Fig. 3).…”