PHARMACOKINETICS OF THE INFUSION OF ALFENTANIL IN MAN

The pharmacokinetics of alfentanil under the conditions of anempirically derived 1 -h continuous infusion of 3µg kg^–1min^–1, with a bolus of 80 µg 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, V^area(0.44±0.15 litre kg^–1) and elimination clearance(3.33 ± 0.75 ml kg^–1 min^–1) were nimilarto those previously reported for a single bolus of alfentanil.These values for apparent volume of distribution and clearancecan be used to calculate correct bolus and infusion doses tomaintain any desired steady state plasma concentration usingstandard formulae: for example, to maintain a steady state plasmaconcentration of 400 ng ml^–1, a bolus doseof 176 µgkg^–1 and an infusion of 1.3 µg kg^–1min wouldbe required.