Vecuronium

Vecuronium is an intermediate-acting aminosteroid non-depolarising neuromuscular blocking drug with minimal cardiovascular effects and no histamine release. It is widely used for intubation and maintenance of relaxation, particularly in patients with cardiovascular disease. Its active metabolite can accumulate in intensive care and cause prolonged weakness.

Class. Non-depolarising neuromuscular blocking drug (aminosteroid).

Mechanism. Competitive antagonism of acetylcholine at the nicotinic receptor of the motor end plate.

Pharmacokinetics. Onset 2 to 3 minutes at 0.1 mg/kg and 90 to 120 seconds at 0.2 mg/kg. Clinical duration 25 to 40 minutes. Elimination half-life 50 to 80 minutes. Eliminated mainly by the liver (30 to 40% metabolised to 3-desacetylvecuronium, which has about 50% of its potency) and bile, with 20 to 30% excreted in urine. Hepatic and renal impairment prolong the effect.

Indications are tracheal intubation, maintenance of muscle relaxation during surgery, and mechanical ventilation in intensive care.

Adults

• Intubation: 0.08 to 0.1 mg/kg intravenously. A dose of 0.15 mg/kg gives faster onset at the cost of a longer duration.
• Maintenance: 0.02 to 0.03 mg/kg boluses every 15 to 25 minutes, or infusion 0.8 to 1.4 micrograms/kg/minute (about 1 microgram/kg/minute) after early recovery.
• Intensive care infusion: 0.8 to 1.2 micrograms/kg/minute, titrated by train-of-four monitoring; limit duration.
• Obesity: dose by ideal body weight.
• Older adults: reduce doses by 25 to 50% and extend intervals.
• No fixed maximum dose; titrate to effect.

Children

• Over 1 year: similar to adults at 0.08 to 0.1 mg/kg; shorter dosing intervals may be needed.
• Infants 7 weeks to 1 year: more sensitive; start at 0.05 to 0.1 mg/kg and titrate.
• Neonates under 7 weeks: use cautiously with a reduced dose and monitor.

Reversal. Sugammadex 2 to 4 mg/kg when the train-of-four count is at least 2, or neostigmine 50 micrograms/kg with glycopyrronium 10 micrograms/kg.

Contraindications. Hypersensitivity to vecuronium or bromide; absence of airway skills, ventilation equipment and reversal agents. Use only with specialist advice in myasthenia gravis.

Boxed-warning-level risks. Anaphylaxis; prolonged paralysis in liver or kidney failure; residual block; intensive care acquired weakness with long infusion and corticosteroids.

Adverse effects. Common: mild injection discomfort, small changes in heart rate and blood pressure. Serious: anaphylaxis, prolonged block, persistent weakness after intensive care, residual paralysis with aspiration risk.

Interactions. Volatile anaesthetics reduce the dose needed by 25 to 50%. Aminoglycosides, clindamycin, magnesium, lithium and calcium channel blockers prolong the block. Long term antiepileptics reduce the effect. Previous suxamethonium can potentiate the block. Corticosteroids add to myopathy risk.

Common prescribing errors. Giving full dose to a patient with liver failure or cholestasis; leaving a long infusion running without train-of-four monitoring; not reversing; using actual instead of ideal body weight in obesity.

Special groups

• Pregnancy: limited transfer; used for caesarean section. Magnesium for pre-eclampsia strongly potentiates it.
• Breastfeeding: compatible after recovery.
• Older adults: lower dose, longer duration.
• Kidney impairment: prolonged duration, particularly of the metabolite; reduce doses in a creatinine clearance of 30 mL/minute or less.
• Liver impairment: prolonged duration; reduce doses and extend intervals.
• Regional: the powder is stable and cheap, which keeps vecuronium in common use; check reconstitution and expiry times.

Formulations. Powder for reconstitution, 10 mg vials.

Administration. Reconstitute 10 mg with 5 mL of sterile water to give 2 mg/mL, or dilute further with 0.9% sodium chloride or 5% glucose. Use within 24 hours of reconstitution if stored at 2 to 8 degrees Celsius; discard unused portions. Give as an intravenous bolus followed by a flush.

Baseline. Neuromuscular disease, liver and kidney function, electrolytes (magnesium, potassium, calcium), body weight, current medicines.

Monitoring. Continuous electrocardiogram, oxygen saturation and capnography. Train-of-four monitoring during use, and a ratio of at least 0.9 before extubation. Daily interruption or review of infusions in intensive care.

Therapeutic drug monitoring. Not used.

Dose reduction and stopping thresholds. Reduce or stop the infusion when the train-of-four count is 1 to 2 or lower. Avoid prolonged infusions in liver or kidney failure.

Referral and escalation. Prolonged weakness needs ventilatory support, correction of electrolytes and acidosis, reversal with sugammadex, and neurological assessment if it persists. Anaphylaxis needs intramuscular adrenaline.