Fentanyl

Fentanyl - is 100 times as potent as morphine. Its onset of action is within 1–2 min after IV injection and a peak effect within 4–5 min. Duration of action after a single bolus is 20 min.The context sensitive half-life following IV infusion is prolonged because of its large volume of distribution.

Uses
Analgesia

Contraindications
Airway obstruction

Administration
• For sedation
IV infusion: 1–5 μg/kg/h

• During anaesthesia
  IV bolus:
  • 1–3 μg/kg with spontaneous ventilation
  • 5–10 μg/kg with IPPV
  • 7–10 μg/kg to obtund pressor response of laryngoscopy
  • Up to 100 μg/kg for cardiac surgery

How not to use fentanyl
In combination with an opioid partial agonist, e.g. buprenorphine
(antagonises opioid effects)
Adverse effects
Respiratory depression and apnoea
Bradycardia and hypotension
Nausea and vomiting
Delayed gastric emptying
Reduce intestinal mobility
Biliary spasm
Constipation
Urinary retention
Chest wall rigidity (may interfere with ventilation)
Muscular rigidity and hypotension more common after high dosage

Cautions
Enhanced sedation and respiratory depression from interaction with:
• benzodiazepines
• antidepressants
• anti-psychotics
Head injury and neurosurgical patients (may exacerbate ↑ ICP as a result of ↑ PaCO2)

Organ failure
Respiratory: ↑ respiratory depression
Hepatic: enhanced and prolonged sedative effect