Overview of the different classes of anaesthetic drugs, their mechanism of action, and common uses in clinical practice.
Introduction to Anaesthetic Drugs
Designed as a quick‑reference guide for students and health‑care professionals.
| Aspect | Definition |
|---|---|
| Purpose | To induce a reversible loss of sensation (pain, temperature, pressure) and, when required, loss of consciousness. |
| Types of effects | • Analgesia – pain relief • Amnesia – loss of memory of the event • Muscle relaxation – facilitates surgery • Unconsciousness – general anaesthesia |
| Routes of administration | Inhalational (gas/vapour), intravenous (IV), intramuscular (IM), oral, topical, epidural/spinal. |
| Class | Main agents | Typical clinical use | Key pharmacologic features |
|---|---|---|---|
| Inhalational (volatile) agents | Sevoflurane, Desflurane, Isoflurane, Halothane (rare) | Maintenance of general anaesthesia (GA) | Low blood‑gas partition coefficient → rapid induction/recovery; dose‑dependent respiratory depression; minimal metabolism (except halothane). |
| Intravenous induction agents | Propofol, Etomidate, Thiopental, Ketamine | Induction of GA; sedation; procedural anaesthesia | • Propofol – rapid onset, anti‑emetic, dose‑dependent hypotension. • Etomidate – hemodynamically stable, adrenal suppression. • Thiopental – barbiturate, long‑acting. • Ketamine – dissociative, stimulates sympathetic tone, preserves airway reflexes. |
| Opioid analgesics | Fentanyl, Sufentanil, Remifentanil, Morphine, Hydromorphone | Intra‑operative analgesia; postoperative pain control | Potent µ‑receptor agonists; respiratory depression; remifentanil unique for rapid metabolism by plasma esterases. |
| Neuromuscular blocking agents (NMBAs) | Depolarizing: Succinylcholine Non‑depolarizing: Rocuronium, Vecuronium, Atracurium, Cisatracurium |
Facilitate tracheal intubation & muscle relaxation | Succinylcholine – rapid onset, short duration, contraindicated in hyperkalemia. Non‑depolarizers – longer acting, reversed with anticholinesterases (neostigmine) or sugammadex (rocuronium, vecuronium). |
| Adjuncts & adjuvants | Midazolam, Dexmedetomidine, Lidocaine, Magnesium, Anticholinergics (glycopyrrolate, atropine) | Sedation, anxiolysis, blunting of sympathetic response, reduction of anesthetic dose | Benzodiazepines → amnesia, anxiolysis; Dexmedetomidine → sedation with minimal respiratory depression; Lidocaine → IV analgesia, reduces cough on emergence. |
| Local anaesthetics | Lidocaine, Bupivacaine, Ropivacaine, Mepivacaine | Regional blocks, infiltration, epidural/spinal anaesthesia | Block Na⁺ channels → prevent depolarization. Duration & potency depend on lipid solubility and protein binding. |
| Parameter | Description | Clinical implication |
|---|---|---|
| Onset of action | Determined by drug’s lipid solubility, pKa, and route | Faster onset → easier airway |