• Suxamethonium

     
       

    Daniel Jolley.

    13 articles.

    Created January 27, 2022, last updated 4 months ago.


    Collection: 151, Score: 183, Trend score: 0, Read count: 183, Articles count: 13, Created: 2022-01-27 01:23:35 UTC. Updated: 2022-01-27 01:44:51 UTC.

    Notes

    reference
    1

    Suxamethonium chloride (suxamethonium, succinylcholine or sux) is a depolarising muscle relaxant that produces rapid-onset, short-duration, deep muscle relaxation. First identified in 1906 and used medically in 1951, it is one of the oldest anaesthesia drugs still widely used. Due to its unique properties and low cost, it remains on the World Health Organisation's List of Essential Medicines

    A. Physiochemistry

    • (CH3)3-N-CH2CH2-OCO-CH2CH2-OCO-CH2CH2-N-(CH3)3
    • pH 3.5
    • Shelf life 3 years at 4°C, though only 'months' at 20°C.

    B. Pharmacokinetics

    1. Dose - ED95 0.5 mg/kg, IV 1.5 mg/kg, IM 2.5-4 mg/kg.
    2. Absorption - IM, IV.
    3. Distribution - >0.2 L/kg; crosses placenta slightly but little effect on foetus.
    4. Protein binding ?
    5. Onset 30s IV, 2-3 min IM; Offset 3-5 min.
    6. Metabolism - PChE to succinylmonocholine (5% activity) & choline -> succinic acid & choline.
      • tß½ 5 minutes

    C. Pharmacodynamics

    1. Mechanism - binds to alpha subunit of nicotinic ACh receptor, producing persistent depolarisation (phase 1 & phase 2 blocks).
    2. CNS - ⇡ intra-ocular pressure (4-8 mmHg rise), ⇡ intra-celebral pressure (to 30 mmHg at 2-4 min).
    3. CVS - arrhythmias (both bradycardia & tachycardia possible), ⇡ systolic blood pressure, (both negative inotropic and chronotropic effects).
    4. Resp - 'sux apnoea' pharmacogenetic diversity (94% normal, 3.8% heterozyg (10 min duration of effect), <1% homozog (1-2h duration))
    5. Renal - hyperkalaemia due to K+ release from muscle; beware in neuromuscular conditions, denervation, and extensive burns.
    6. GIT - ⇡ intragastric pressure, ⇡ secretions, salivation.
    7. SEs - anaphylaxis, malignant hyperthermia, sux apnoea, muscle pains, masseter spasm.
    Daniel Jolley  Daniel Jolley
     
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