The patient is started on appropriate treatment and reports significant symptom improvement. However, she now has abdominal cramping, nausea, sweating, and diarrhea. Which of the following agents can be used to effectively control these new symptoms?

Question

The patient is started on appropriate treatment and reports significant symptom improvement.  However, she now has abdominal cramping, nausea, sweating, and diarrhea.  Which of the following agents can be used to effectively control these new symptoms?

Quizplus · Accepted Answer

11ec160b_3b0b_72f9_9249_398c44aaf985_MD0001_00 The treatment of myasthenia gravis typically involves the use of a cholinesterase inhibitor, an immunosuppressive agent, and possible thymectomy. This patient is most likely receiving treatment with a cholinesterase inhibitor, such as pyridostigmine, which inhibits the degradation of acetylcholine in the neuromuscular junction. This improves skeletal muscle weakness but can cause muscarinic overstimulation of the smooth muscles and excessive glandular secretions (eg, diarrhea, diaphoresis, abdominal cramping, emesis). Selective muscarinic antagonists (eg, glycopyrrolate, hyoscyamine, propantheline) can be used to reduce the side effects of cholinesterase inhibitors in sites where acetylcholine action is mediated by muscarinic receptors (ie, gastrointestinal tract). Because of their selectivity, these drugs improve side effects without affecting the action of cholinesterase inhibitors on skeletal muscle, which uses nicotinic receptors. (Choice A) Fluoxetine is a selective serotonin reuptake inhibitor used primarily in the treatment of depression. It acts in a fashion similar to the cholinesterase inhibitors in that it prolongs the activity of a neurotransmitter on its target tissue. However, it is otherwise unrelated to cholinesterase inhibitors or their effects. (Choice C) Pilocarpine is a nonselective muscarinic receptor agonist. Use of this agent would worsen this patient's side effects. (Choices D and E) Prazosin is an alpha-1 adrenergic antagonist, and propranolol is a beta adrenergic antagonist. Use of either agent does not prevent the side effects of a cholinesterase inhibitor. Educational objective: The treatment of myasthenia gravis involves the use of a cholinesterase inhibitor, immunosuppressants, and possible thymectomy. Cholinesterase inhibitors may cause adverse effects related to muscarinic overstimulation, which can be ameliorated by the use of an antimuscarinic agent such as glycopyrrolate, hyoscyamine, or propantheline.

The Patient Is Started on Appropriate Treatment and Reports Significant