The use of edrophonium chloride to test for the presence of myasthenia gravis. The appropriate dose is injected intravenously; if there is no effect, a larger dose is given within 45 sec. A positive test demonstrates brief improvement in strength unaccompanied by lingual fasciculation. The test may also be used to determine an overdose of a cholinergic drug. An excessive dose of cholinergic drug produces weakness that closely resembles myasthenia. A very small dose of edrophonium chloride given intravenously worsens the weakness if it is due to cholinergic drug overdose and improves it if it is due to myasthenia gravis.
CAUTION!The test should not be performed unless facilities and staff for respiratory resuscitation are immediately available.
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