Edrophonium test

The edrophonium test is probably the most readily accessible test to confirm the diagnosis of MG. It can be performed in any clinical setting provided that facilities are available to counteract hypotension and respiratory failure. Edrophonium is given intravenously, first 2 mg (0.2 ml) as test dose while monitoring the patient's heart rate (atropine (0.4 mg) should be available in case of exaggerated bradycardia). If no adverse effects occur after 1 min, another 3 mg is given. In the majority of patients clinical improvement (resolution of diplopia or ptosis or....) will be observed within 30 to 60 seconds after the 5 mg has been given and lasts for about 5 minutes and then quickly disappears. Although the test is very sensitive it is not at all specific, since other neuromuscular disorders (e.g. Lambert Eaton syndrome), motor neuron disease etc. could also show a positive response.