Edrophonium test (Tensilon test)
How is the Edrophonium test (Tensilon test) performed?
The patient must have readily observable weakness (e.g., ptosis) or weakness that is easily quantified on examination.
The test must be performed in a controlled setting, with emergency resuscitation equipment and trained personnel available, because there is a small risk of precipitating cardiac arrhythmia.
Both a syringe containing normal saline (the placebo) and a syringe containing edrophonium (10 mg) must be prepared.
The placebo is always administered first, and the same protocol should be used for both IV preparations.
A test dose of 1 mg is given, and the patient is observed for side effects over 5 minutes (i.e., flushing, palpitations, tearing).
In some patients, clinical effect appears at this small dose. In most of them, however, the remaining 10 mg will be required.
Each minute for the next 5 minutes after administration, the patient should be observed and tested for improvement, and the results documented.
Unequivocal improvement occurring only with edrophonium and not with placebo supports the diagnosis of MG.
