## Most Common Depolarising Muscle Relaxant **Key Point:** Succinylcholine (suxamethonium) is the ONLY depolarising muscle relaxant in clinical use worldwide and remains the gold standard for rapid sequence intubation due to its ultra-short duration of action. ### Why Succinylcholine Dominates 1. **Mechanism**: Depolarising agent — acts as acetylcholine agonist, causes sustained depolarisation and fasciculations 2. **Onset**: 30–60 seconds (fastest of all muscle relaxants) 3. **Duration**: 5–10 minutes (metabolised by plasma pseudocholinesterase) 4. **Clinical use**: RSI, emergency intubation, short procedures ### Comparison with Other Options | Agent | Type | Status | Reason for Non-use | | --- | --- | --- | --- | | **Succinylcholine** | Depolarising | **In use** | Gold standard for RSI | | Decamethonium | Depolarising | Obsolete | Longer duration, more side effects; withdrawn from most countries | | Mivacurium | Non-depolarising | In use | Slower onset (2–3 min); not ideal for RSI | | Doxacurium | Non-depolarising | In use | Slow onset (4–5 min); not suitable for emergency intubation | **High-Yield:** Succinylcholine is the ONLY depolarising agent available clinically. All other depolarising agents (decamethonium, dimethyl tubocurarine) are historical or withdrawn. ### Side Effects of Succinylcholine - **Fasciculations** → risk of postoperative myalgia, hyperkalemia, increased ICP, increased intraocular pressure - **Malignant hyperthermia** (rare but life-threatening) - **Bradycardia** (especially in children) - **Histamine release** (minimal) - **Contraindications**: Pseudocholinesterase deficiency, family history of MH, burns, crush injuries, denervation injuries, spinal cord injury **Clinical Pearl:** In RSI, succinylcholine is preferred over rocuronium despite rocuronium's safety profile because of succinylcholine's faster onset and shorter duration, allowing rapid airway assessment if intubation fails.
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.