Pharmacokinetics of alfentanil during and after a fixed rate infusion.
Twenty-nine patients (age range 14-81 yr) undergoing orthopaedic surgery received alfentanil 100 micrograms kg-1 given as two i.v. boluses followed by a fixed rate infusion of 1 micrograms kg-1 min-1 for 44-445 min. Additional 1-mg bolus doses of alfentanil were administered as required. Plasma samples were assayed for alfentanil using radioimmunoassay. Pharmacokinetic parameters were estimated by a model-independent approach and by curve-fitting. Regression analysis showed no statistical relationship between T 1/2 beta, Cl or Vd and the duration of the infusion, total dose or body weight. We found no significant correlation between age and T 1/2 beta of alfentanil for patients younger than 40 yr. For patients older than 40 yr, T 1/2 beta increased linearly with age. There was no significant decrease in Cl with age, although the lower values for Cl (100-200 ml min-1) were generally found in subjects older than 60 yr. The present study demonstrated that a 100-micrograms kg-1 loading dose and a 1-micrograms kg-1 min-1 infusion may be appropriate for analgesia in general surgical procedures.
Van Beem
H
H
Department of Anaesthesia, University of Nijmegen, the Netherlands.
Van Peer
A
A
Gasparini
R
R
Woestenborghs
R
R
Heykants
J
J
Noorduin
H
H
Van Egmond
J
J
Crul
J
J
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015760:Alfentanil; D000777:Anesthetics / Q000008:administration & dosage / Q000493:pharmacokinetics*; D001835:Body Weight; D005260:Female; D005283:Fentanyl / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male; D008875:Middle Aged; D009985:Orthopedics; D013997:Time Factors
D000777:Anesthetics; D015760:Alfentanil; D005283:Fentanyl