CLASS
Non-depolarising neuromuscular blocker
PRESENTATION
Clear, colourless solution.
Formulations
- 5ml vial; 50mg, 10mg/ml
INDICATIONS & DOSING
Paralysis; endotracheal intubation, surgical immobility, ventilator synchrony/chest-wall compliance, facilitate pneumoperitoneum/reduce intra-abdominal pressure, prevention of shivering/coughing
- Adult; 40-70mg IV (routine), 70-100mg IV (modified rapid sequence induction)
- Paediatric; 0.6mg/kg IV, 1mg/kg IV (modified rapid sequence induction)
PRACTICALITIES
Administration
- Administered as neat solution
- Care to prevent accidental storage of neuromuscular blocker within the IV set following administration; may result in subsequent undesired paralysis and respiratory arrest
Incompatibilities
- Alkaline solutions; thiopentone
- Antibiotics; cephazolin, amoxicillin, vancomycin, others
- Others; dexamethasone, insulin, intralipid, frusemide
Practice tips
- Titrate to desired depth of paralysis via neuromuscular monitoring
- Dose according to ideal body weight cf. total body weight
- Subsequent maintenance dosing is dependent on required depth/duration; ~20% of the establishment dose is required to maintain paralysis due to partial receptor occupation
- Unopened vials are stable for 12 weeks if stored at room temperature
- Faster onset/offset in paediatric population and high cardiac output states
- Slower offset with hypothermia, acidaemia, hypokalaemia, hypocalcaemia, hypermagnesaemia
PHARMACOKINETICS
Onset
- 0.6mg/kg IV; 2-3 minutes
- 1mg/kg IV; 60-90 seconds
Duration of action
- 0.6mg/kg IV; 30-40 minutes
- 1mg/kg IV; 60 minutes
Metabolism
- Minimal hepatic metabolism to inactive compounds
Elimination
- Majority biliary excretion in unchanged form
- 1/3 renal excretion
MECHANISM
Non-depolarising competitive inhibition of acetylcholine receptors at the neuromuscular junction prevents neuromuscular transmission and muscle depolarisation.
DESIRED CLINICAL EFFECTS
Airway
- Facilitation of endotracheal intubation; relaxation of vocal cords, ablation of airway reflexes
Respiratory
- Improved chest-wall compliance
- Improved ventilator synchrony
- Prevention of coughing (and associated rises in ICP)
Musculoskeletal
- Flaccid paralysis; surgical immobility, prevention of ECT-related injury, prevention of shivering (oxygen consumption)
Gastrointestinal
- Relaxation of abdominal wall musculature; reduction in intra-abdominal pressure (facilitation of pneumoperitoneum, intra-abdominal compartment syndrome)
OTHER CLINICAL EFFECTS, ADVERSE EFFECTS & TOXICITIES
Respiratory
- Respiratory arrest
- Residual paralysis; micro-aspiration, pneumonia, respiratory failure
Neurological
- Awareness under anaesthesia
Immune
- Anaphylaxis
Musculoskeletal
- ICU-Acquired Weakness (ICUAW); association only
Antidote
- Sugammadex
- Neostigmine (competitive)
CONSIDERATIONS
Precautions
- Renal/hepatic impairment; prolongation of neuromuscular blockade (more clinically relevant with subsequent dosing)
- Disuse atrophy including cachexia, debilitation; profound paralysis
- Neuromuscular disease – myasthenia gravis, Lambert-Eaton syndrome; profound paralysis
- Burns, denervation; resistance to neuromuscular blockade
Obstetric
ADEC category B2
Drug interactions
- Volatile anaesthesia, magnesium, aminoglycosides (gentamicin), lithium; augmentation of neuromuscular blockade
- Phenytoin, carbamazepine, chronic corticosteroids; inhibition of neuromuscular blockade
REFERENCES
Drug information has been compiled from multiple sources including
- Drugs in Anaesthesia and Intensive Care (Scarth & Smith)
- Micromedex (IBM)
- BJA Education (Oxford Academic)
- Pharmacology for Anaesthesia and Intensive Care (Cambridge)
- Australian Prescriber (NPS MedicineWise)