Risk of bradycardia may be increased with second dose and may occur more in children (occurrence may be reduced by pre-treating with atropine). May increase intraocular pressure (caution with narrow-angle glaucoma or penetrating eye injuries). Use may be associated with acute onset of malignant hyperthermia (higher risk if concomitant administration of volatile anesthetics). May increase vagal tone. Use with caution in extensive or severe burns (risk of hyperkalemia). Alkalosis, hypercalcemia, demyelinating lesions, peripheral neuropathies, denervation, infection, muscle trauma, and diabetes mellitus may result in antagonism of neuromuscular blockade. Electrolyte abnormalities, severe hyponatremia, severe hypocalcemia, severe hypokalemia, hypermagnesemia, neuromuscular diseases, acidosis, acute intermittent porphyria, Eaton-Lambert syndrome, myasthenia gravis, renal failure, and hepatic failure may result in potentiation of neuromuscular blockade. Use with caution in patients suspected of being homozygous for the atypical plasma cholinesterase gene. Plasma cholinesterase activity may also be reduced by burns, decompensated heart disease, infections, malignant tumors, myxedema, pregnancy, severe hepatic or renal dysfunction, ulcer, and certain medications and chemicals. Use with caution in the elderly; effects and duration are more variable. Acute rhabdomyolysis with hyperkalemia, ventricular arrhythmias and cardiac arrest reported (rarely) in children with undiagnosed skeletal muscle myopathy (use in children should be reserved for emergency intubation or where immediate airway control is necessary). Maintenance of an adequate airway and respiratory support is critical.