Question

Which drug is used to differentiate myasthenia gravis from cholinergic crisis?

• A. Pyridostigmine
• B. Edrophonium
• C. Methacholine
• D. Clonidine

Hint:

The short acting Tensilon (edrophonium) test diagnoses myasthenia.

Answer 1

The Correct Option is B

Step 1: A bedside test needs a cholinesterase inhibitor that acts and wears off within seconds, so the patient can be observed quickly and safely.
Step 2: Edrophonium fits this need. Its action lasts only a few minutes, which is why it is chosen for the diagnostic Tensilon test rather than for ongoing treatment.
Step 3: A small intravenous test dose is given, and if no response appears within about three quarters of a minute the rest of the dose follows. A transient gain in muscle power points to myasthenia gravis, whereas deepening weakness signals a cholinergic crisis.
Step 4: Pyridostigmine is the long acting maintenance drug, methacholine is a direct muscarinic agonist, and clonidine is an alpha 2 agonist, so the diagnostic agent is edrophonium.
\[\boxed{\text{Edrophonium}}\]