Question

A 48-year-old woman has a history of myasthenia gravis. She has been treated with an oral acetylcholinesterase (AChE) inhibitor for several years, and has done well until now. Today she presents in your clinic with muscle weakness and other signs and symptoms that could reflect either a cholinergic crisis (excess dosages of her maintenance drug) or a myasthenic crisis (insufficient treatment). You will use a rapidly acting parenteral acetylcholinesterase inhibitor to help make the differential diagnosis. Which drug would, therefore, be most appropriate to use?

a. Edrophonium
b. Malathion
c. Physostigmine
d. Pralidoxime
e. Pyridostigmine

Answer 1

Edrophonium is the most suitable drug for distinguishing between a cholinergic crisis and a myasthenic crisis in a myasthenia gravis patient. It works by inhibiting acetylcholinesterase, thereby increasing acetylcholine at the neuromuscular junction, which is crucial in the treatment of myasthenia gravis.

Step-by-step explanation:

The rapidly acting parenteral acetylcholinesterase inhibitor most appropriate to use for distinguishing between a cholinergic crisis and a myasthenic crisis in a patient with myasthenia gravis is Edrophonium. This drug quickly improves muscle strength in cases of myasthenic crisis by temporarily inhibiting acetylcholinesterase, thereby increasing the amount of acetylcholine available at the neuromuscular junction. However, if muscle weakness worsens, suggesting a cholinergic crisis due to excess medication, edrophonium should be avoided as it could exacerbate the condition.

Both cholinergic and myasthenic crises involve the balance of acetylcholine in the neuromuscular junction; the proper management of these crises is crucial for the patient's health. Altering how acetylcholinesterase works can significantly influence nerve transmission, making it a target for both therapeutic treatment of conditions like myasthenia gravis and Alzheimer's, as well as the mechanism of action for certain insecticides like malathion.