The clinic nurse is caring for a client with a recent diagnosis of myasthenia gravis. The client has begun treatment with pyridostigmine bromide. What change in status would most clearly suggest a therapeutic benefit of this medication?

Choice A rationale Pyridostigmine bromide is an anticholinesterase inhibitor used to treat myasthenia gravis. It works by preventing the enzyme acetylcholinesterase from breaking down the neurotransmitter acetylcholine (ACh), thereby increasing the concentration of ACh at the neuromuscular junction. This facilitates better transmission of nerve impulses to the muscles, leading directly to improved voluntary muscle strength and endurance, which is the primary therapeutic goal. Choice B rationale Pyridostigmine, by potentiating the effects of acetylcholine, can increase parasympathetic activity. This commonly leads to cholinergic side effects such as increased, not decreased, urination (urinary urgency or frequency), as well as increased salivation, lacrimation, and gastrointestinal motility. A decrease in urination would suggest an ineffective or anticholinergic-like effect, not a therapeutic benefit. Choice C rationale Although pyridostigmine can improve muscle strength, a potential side effect of increased acetylcholine is excessive stimulation of muscarinic receptors in the gut, which results in parasympathetic effects like hypermotility, abdominal cramps, diarrhea, and increased secretions. Therefore, the medication typically causes worse, not improved, gastrointestinal function. Choice D rationale Myasthenia gravis is a disorder affecting the neuromuscular junction, causing muscle weakness. Pyridostigmine's action is localized to increasing acetylcholine availability at this junction to improve muscle function. It does not directly target or improve cognitive function, which is generally unaffected in myasthenia gravis, making this an irrelevant measure of therapeutic benefit.