Pharmacotherapeutic group: Analgesics. Opioids. Phenylpiperidine derivatives.
ATCvet code: QN02AB03
Pharmacodynamic properties
Fentanyl is a synthetic opioid that is selective for the µ-opioid receptor.
Fentanyl citrate has the ability to produce profound analgesia. It causes only minor heart and circulatory depression.
The principal actions of therapeutic value are analgesia and sedation.
Following intravenous injection fentanyl has a rapid onset of action, although the maximal analgesic and respiratory depressant effects may not occur for several minutes.
Pharmacokinetic properties
After intravenous injection the fentanyl plasma concentrations decrease rapidly primarily due to redistribution. In dogs, fentanyl is 60% bound to plasma proteins. Fentanyl has a large volume of distribution of more than 5 l/kg. The plasma kinetics of fentanyl are independent of the dose in the range of recommended doses.
Fentanyl has a relatively long elimination half-life: 45 minutes to more than 3 hours in dogs. The clearance is high about 40-80 ml/min/kg. It is primarily eliminated by metabolism, with hydroxylation and dealkylation being the primary mechanisms, and less than 8% of the total dose is eliminated as unchanged drug. In addition to hepatic metabolism fentanyl may be metabolised in extra hepatic sites and eliminated by extra renal routes.