Myasthenia gravis, edrophonium diagnosis

The answer is a. (Hardman, pp 161-169.) Although all of the listed compounds inhibit the activity of the cholinesterases, only edrophonium chloride is used in the diagnosis of myasthenia gravis. The drug has a more rapid onset of action (1 to 3 min following intravenous administration) and a shorter duration of action (approximately 5 to 10 min) than pyridostigmine... 

Edrophonium Alcohol, binds briefly to active site of acetylcholinesterase (AChE) and prevents access of acetylcholine (ACh) Amplifies all actions of ACh increases parasympathetic activity and somatic neuromuscular transmission Diagnosis and acute treatment of myasthenia gravis Parenteral quaternary amine does not enter CNS Toxicity Parasympathomimetic excess Interactions Additive with parasympathomimetics... 

The actions of edrophonium [ed roe FOE nee um] are similar to those of neostigmine, except that it is more rapidly absorbed and has a short duration of action (10-20 minutes). Edrophonium is a quarternary amine and is used in the diagnosis of myasthenia gravis. Intravenous injection of edrophonium leads to a rapid increase in muscle strength. Care must be taken since excess drug may provoke a cholinergic crisis. Atropine is the antidote. 

Edrophonium is an anticholinesterase muscle stimulant that facihtates myoneural junction impulse transmission by inhibiting acetylcholine destmction by cholinesterase. It is indicated in differential diagnosis of myasthenia gravis as an adjunct in evaluating treatment of myasthenia gravis in evaluation of aner-gency treatment of myasthenic aises in reversal of neuromuscular blockade by curare gallamine or tubo-curarine and in treatment of respiratory depression caused by curare overdose. 

Edrophonium is very short-acting, so is not used for treatment. Its major uses are in diagnostic procedures, such as the diagnosis of myasthenia gravis. It is also used to reverse the effects of competitive neuromuscular blockade (e.g., d-tubocurarine) after surgery. 

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