Pharmacology III – CNS Module Practice Exam

A myasthenic crisis is a severe exacerbation of myasthenia gravis symptoms, primarily characterized by respiratory failure due to weakness of the respiratory muscles. This crisis can be triggered by several factors, with under-dosing of anticholinesterase medication being a primary trigger.

Anticholinesterase medications, such as pyridostigmine, are essential for managing myasthenia gravis because they inhibit the breakdown of acetylcholine, thereby increasing its availability at the neuromuscular junction. When a patient does not receive an adequate dose of these medications, the decreased availability of acetylcholine leads to increased muscle weakness, particularly affecting the respiratory muscles, hence precipitating a myasthenic crisis.

In contrast, overdosing on anticholinesterase medication can lead to cholinergic crisis, which is characterized by symptoms such as muscle twitching, cramping, and increased salivation, rather than the worsening weakness seen in myasthenic crisis. High sodium intake and excessive physical activity might exacerbate myasthenia gravis symptoms but are not recognized as direct triggers for a crisis in the same manner as inadequate medication management.