title: Evaluation of diurnal variation in fentanyl clearance.
abstract: Drug disposition kinetics are commonly assumed to be time-invariant as a first approximation. In a preliminary study, 6 healthy volunteers received a constant intravenous infusion of 50 micrograms/h for 48 hours; the serum fentanyl concentration at 36 hours was lower than that at 24 hours for all 6 subjects. This suggested possible diurnal variations in fentanyl clearance. In 2 subsequent studies, with healthy volunteers receiving short infusions of fentanyl (n = 9, 150 micrograms/h for 0.33 hours every 4 hours; n = 12, 150 micrograms/h for 0.33 hours every hour, respectively), the area under the serum fentanyl concentration curve appeared to be independent of the time of infusion. Thus, there was no evidence to support a large diurnal change in fentanyl clearance. The serum fentanyl concentration-time profiles, corrected for carryover from previous doses, within each study were superimposable. This suggests that there are no diurnal changes in the distribution kinetics of fentanyl.
authors.affiliation: Alza Corporation, Palo Alto, California 94303-0802, USA.
authors.forename: S K
authors.initials: SK
authors.lastname: Gupta
authors.forename: M A
authors.initials: MA
authors.lastname: Southam
authors.forename: S S
authors.initials: SS
authors.lastname: Hwang
mesh_terms: D002940:Circadian Rhythm; D004334:Drug Administration Schedule; D005283:Fentanyl / Q000008:administration & dosage / Q000493:pharmacokinetics*; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male; D008657:Metabolic Clearance Rate; D009271:Naltrexone / Q000008:administration & dosage / Q000494:pharmacology
chemical_list: D009271:Naltrexone; D005283:Fentanyl