Fentanyl

Fentanyl: Uses, Dosage and Side Effects

Overview

• Synthetic pure mu (OP3) receptor agonist.

Uses of Fentanyl

• Very potent opioid analgesic (50 times more potent than morphine) used to provide profound intraoperative analgesia in dogs and cats.
• Can also be used at low dose rates for postoperative analgesia.
• Transdermal fentanyl patches can be used to provide analgesia for up to 72 hours after surgery or for the management of chronic pain.

Dose of Fentanyl in Dogs and Cats

Dogs:

• Intraoperative analgesia: 5 μg (micrograms)/kg i.v. q20min; 2.5–10 μg/kg/h by continuous rate infusion during anaesthesia, reduced to 1–5 μg/kg/h during the postoperative period.
• Continuous rate infusions should be preceded by a loading dose given slowly i.v. (2.5–10 μg/kg).
• Transdermal patch: 4 μg/kg/h patch (e.g. 100 μg/h patch for a 25 kg dog).

Cats:

• Intraoperative analgesia: 5 μg (micrograms)/kg bolus, repeated injections may be required q20min.
• Anaesthesia: continuous rate infusions as for dogs.
• Transdermal patch: 25 μg/h patch for cats 3–5 kg; in smaller cats and kittens the 12.5 μg/h patch can be applied.

Side Effects of Fentanyl in Dogs and Cats

• Intraoperative administration is likely to cause respiratory depression.
• Rapid i.v. injection can cause severe bradycardia.
• Atropine can be administered to counter bradycardia if necessary.
• Apart from the effects on heart rate, fentanyl has limited other effects on cardiovascular function when used at clinical dose rates.

Contraindications of Fentanyl in Dogs and Cats

• No information is available.

Some Notes:

• Fentanyl can be used to reduce the dose requirement for other anaesthetic drugs in patients with cardiovascular instability or systemic disease.