Suxamethonium
Suxamethonium (also known as succinylcholine) is an ultra-short-acting depolarizing neuromuscular blocking agent. It is primarily used in veterinary medicine to facilitate rapid endotracheal intubation and provide skeletal muscle relaxation during surgery. > **Clinical Pearl:** Because it is a depolarizing agent, its use is often preceded by transient muscle fasciculations. It provides **no analgesia or sedation**; patients must be fully anesthetized and mechanically ventilated.
Mechanism: Competitively binds to the **nicotinic acetylcholine receptor** at the neuromuscular junction. The persistent depolarization prevents the transmission of further action potentials → resulting in flaccid muscle relaxation.
Routes of administration
Contraindications
- Patients with pre-existing hyperkalemia
- Glaucoma or penetrating eye injuries
- Severe liver disease
- Patients with known atypical plasma pseudocholinesterase
- Conscious patients (must be fully anesthetized)
Adverse effects
- Muscle fasciculations
- Hyperkalemia
- Bradycardia or arrhythmias
- Malignant hyperthermia
- Increased intraocular pressure
- Increased intragastric pressure
- Prolonged apnea
Drug interactions
- Organophosphates · Inhibit pseudocholinesterase, leading to significantly prolonged neuromuscular blockade · major
- Carbamates · Inhibit pseudocholinesterase, leading to significantly prolonged neuromuscular blockade · major
- Aminoglycosides · May enhance or prolong neuromuscular blockade · moderate
- Volatile anesthetics · Enhanced neuromuscular blockade and increased risk of malignant hyperthermia · major
Monitoring
- Heart rate and rhythm (ECG)
- Blood pressure
- Oxygen saturation (SpO2)
- End-tidal CO2 (Capnography)
- Body temperature (monitor for malignant hyperthermia)
- Peripheral nerve stimulation (Train-of-Four) to assess blockade depth and recovery
Overdose
Overdose results in prolonged neuromuscular blockade and extended apnea. **Treatment is strictly supportive** with continuous mechanical ventilation and maintenance of anesthesia until the drug is fully metabolized and spontaneous respiration returns. **There is no specific pharmacological reversal agent** for depolarizing neuromuscular blockers.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.