A diagnostic test for suspected myasthenia gravis uses edrophonium chloride (Tensilon). What is the expected outcome after administration?

A diagnostic test for suspected myasthenia gravis uses edrophonium chloride (Tensilon). What is the expected outcome after administration?

• A. Increased muscle weakness
• B. No change in strength
• C. Decreased muscle weakness
• D. Onset of seizures

Answer: (C)

Edrophonium chloride briefly inhibits acetylcholinesterase, raising acetylcholine levels at the neuromuscular junction. In myasthenia gravis, where antibody damage reduces functional receptor activity, this extra acetylcholine temporarily improves transmission across the NMJ. The result is a quick, transient improvement in muscle strength, especially in fatigable muscles like the eyelids and proximal muscles. So the expected outcome is a decrease in muscle weakness after the dose. (No change or worsening would argue against MG, and seizures are not a typical effect of this test.)

Edrophonium chloride briefly inhibits acetylcholinesterase, raising acetylcholine levels at the neuromuscular junction. In myasthenia gravis, where antibody damage reduces functional receptor activity, this extra acetylcholine temporarily improves transmission across the NMJ. The result is a quick, transient improvement in muscle strength, especially in fatigable muscles like the eyelids and proximal muscles. So the expected outcome is a decrease in muscle weakness after the dose. (No change or worsening would argue against MG, and seizures are not a typical effect of this test.)