A patient being diagnosed for myasthenia gravis would be expected to have improved neuromuscular function after being treated with Edrophonium and not with neostigmine, why?
Well, edrophonium is preferred because it is relatively shorter in action than the neostigmine, but we can use the neostigmine if the edrophonium is not available. In both conditions we must give atropine before using these two drugs to prevent the cardiac arrest which may occur due to the action of these drugs on the cardiac muscle. Anyhow, the edrophonium is used for the diagnosis of myasthenia graves because it increases the secretion of the Ach in the neuromuscular junctions which can overcome Ach receptors defect leading to sudden, short lasting improvement followed by decrease muscle strength again. Edrophonium is used for the diagnosis of MG but not for the treatment because it is very short acting.
