Issues for Surgery
Increase in muscle weakness, potentially including respiratory muscles, if omitted.
Interaction with neuromuscular blockers if continued (see Interaction(s) with Common Anaesthetic Agents).
Advice in the Perioperative period
Elective and Emergency Surgery
Ensure Anaesthetist is aware of the drug interactions.
Interaction(s) with Common Anaesthetic Agents
Local or regional anaesthesia is often preferred in myasthenia gravis; however, the dose of ester local anaesthetics may need to be reduced due to concomitant pyridostigmine or neostigmine treatment1.
Neuromuscular Blocking Drugs (NMBDs)
Pyridostigmine and neostigmine antagonise the effect of NMBDs and neostigmine is routinely used for reversal1, 2, 3. However, in patients with myasthenia gravis reversal can be unpredictable, partially due to chronic anticholinesterase treatment. Excessive administration of reversal agents could precipitate cholinergic crisis1, 4, 5.
Unlike non-depolarising NMBDs, administration of pyridostigmine or neostigmine increases the concentration of acetylcholine at the neuromuscular junction and thus prolongs the action of suxamethonium 1, 4, 5. Ideally suxamethonium should be avoided in patients with myasthenia gravis.
Pyridostigmine and neostigmine can increase the risk of bradycardia when used concomitantly with the following6: -
Interaction(s) with other Common Medicines used in the Perioperative Period
Aminoglycoside antibiotics (e.g. amikacin, gentamicin, neomycin, streptomycin, tobramycin) are contraindicated in patients with myasthenia gravis as they impair neuromuscular transmission6.
The stress of surgery and potential exposure to exacerbating drugs can trigger a myasthenia crisis5.