SN6 SHORT NOTE 5M ★ High-yield

Write a short note on Fentanyl.

General Surgery · Final Professional

Pharmacology

Fentanyl is a synthetic opioid and a potent μ-receptor agonist, roughly 100 times as potent as morphine. It is highly lipid-soluble, giving a rapid onset and short duration after a bolus (offset by redistribution), which makes it a mainstay of intra-operative analgesia and of blunting the pressor response to laryngoscopy.

Uses & Effects

It is used to provide analgesia during anaesthesia, as part of balanced anaesthesia, and for procedural and postoperative pain. Effects (class effects of μ-agonists): analgesia, respiratory depression (dose-dependent — the main danger), sedation, bradycardia, nausea/vomiting, miosis, and (with large/repeated doses) accumulation. Unlike morphine it causes little histamine release.

DANGER / REMEMBER

The principal danger of fentanyl (and all opioids) is dose-dependent respiratory depression, potentiated by other sedatives; monitor ventilation and oxygenation, and remember its effect can outlast a single stimulus. Reverse with naloxone if needed.

CLINICAL PEARL

Fentanyl — ~100× morphine, fast on/short (redistribution), little histamine — is the workhorse intra-operative opioid; its cardinal risk is respiratory depression, reversible with naloxone. Related agents: alfentanil (faster), remifentanil (ultra-short, esterase-metabolised).

Related Opioids

Fentanyl belongs to a family of synthetic opioids that differ mainly in their speed and duration: alfentanil has a faster onset and shorter action, useful for brief intense stimuli, while remifentanil is metabolised by non-specific tissue and plasma esterases so that its effect ends within minutes of stopping an infusion regardless of how long it has run, making it ideal for titratable intra-operative analgesia. All share the μ-agonist effects and the cardinal danger of respiratory depression, and all can be reversed by naloxone, so the choice between them is largely a matter of the required onset and offset.

CLINICAL PEARL

Fentanyl is the intra-operative opioid workhorse: about a hundred times as potent as morphine, quick on and short after a bolus because of redistribution, with little histamine release — and, like every opioid, dangerous chiefly for its respiratory depression, which naloxone reverses.

Chest wall rigidity may follow rapid high-dose injection.

KEY POINT

Key points TO remember

Fentanyl: synthetic μ-agonist ~100× morphine; lipid-soluble → rapid onset, short bolus action.
Used for intra-operative & procedural analgesia; blunts laryngoscopy pressor response.
Effects: analgesia, respiratory depression (main danger), bradycardia, nausea; little histamine.
Reverse with naloxone; relatives alfentanil (faster) & remifentanil (ultra-short).

EXAM TIP

Sources: Morgan & Mikhail’s Clinical Anesthesiology; Miller’s Anesthesia; Ajay Yadav’s Short Textbook of Anaesthesia.

All questions in Intravenous Anaesthetic Agents

Every General Surgery chapter →