Pharmacokinetics of fentanyl, alfentanil, and sufentanil in isoflurane-anesthetized cats

• Published in: Journal of veterinary pharmacology and therapeutics Vol. 37; no. 1; pp. 13 - 17
• Main Authors: Pypendop, B. H., Brosnan, R. J., Majewski-Tiedeken, C. R., Stanley, S. D., Ilkiw, J. E.
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01.02.2014
• Subjects: Alfentanil - administration & dosage; Alfentanil - blood; Alfentanil - pharmacokinetics; Anesthesia, Inhalation; Anesthetics, Inhalation; Anesthetics, Intravenous - administration & dosage; Anesthetics, Intravenous - pharmacokinetics; Animals; Area Under Curve; Cats - blood; Cats - metabolism; Drug Interactions; Fentanyl - administration & dosage; Fentanyl - blood; Fentanyl - pharmacokinetics; Half-Life; Isoflurane; Sufentanil - administration & dosage; Sufentanil - blood; Sufentanil - pharmacokinetics
• ISSN: 0140-7783; 1365-2885
• DOI: 10.1111/jvp.12047

The aim of this study was to compare the pharmacokinetics of fentanyl, alfentanil, and sufentanil in isoflurane‐anesthetized cats. Six adult cats were used. Anesthesia was induced and maintained with isoflurane in oxygen. End‐tidal isoflurane concentration was set at 2% and adjusted as required due to spontaneous movement. Fentanyl (10 μg/kg), alfentanil (100 μg/kg), or sufentanil (1 μg/kg) was administered intravenously as a bolus, on separate days. Blood samples were collected immediately before and for 8 h following drug administration. Plasma drug concentration was determined using liquid chromatography/mass spectrometry. Compartment models were fitted to concentration–time data. A 3‐compartment model best fitted the concentration–time data for all drugs, except for 1 cat in the sufentanil group (excluded from analysis). The volume of the central compartment and the volume of distribution at steady‐state (L/kg) [mean ± SEM (range)], the clearance (mL/min/kg) [harmonic mean ± pseudo‐SD (range)], and the terminal half‐life (min) [median (range)] were 0.25 ± 0.04 (0.09–0.34), 2.18 ± 0.16 (1.79–2.83), 18.6 ± 5.0 (15–29.8), and 151 (115–211) for fentanyl; 0.10 ± 0.01 (0.07–0.14), 0.89 ± 0.16 (0.68–1.83), 11.6 ± 2.6 (9.2–15.8), and 144 (118–501) for alfentanil; and 0.06 ± 0.01 (0.04–0.10), 0.77 ± 0.07 (0.63–0.99), 17.6 ± 4.3 (13.9–24.3), and 54 (46–76) for sufentanil. Differences in clearance and volume of distribution result in similar terminal half‐lives for fentanyl and alfentanil, longer than for sufentanil.