A nurse is assessing a client who has Parkinson's disease and is taking levodopa/carbidopa. The nurse observes that the client has tremors and twitching. Which of the following medications should the nurse anticipate administering?

Choice A rationale Metoprolol is a beta-blocker primarily used to treat hypertension, angina, and heart failure. It works by blocking beta-adrenergic receptors, leading to decreased heart rate and blood pressure. It is not indicated for managing tremors or dyskinesias associated with levodopa/carbidopa therapy in Parkinson's disease, as these are typically dopaminergic in origin. Choice B rationale Bethanechol is a muscarinic cholinergic agonist that increases bladder tone and stimulates gastrointestinal motility. It is primarily used for urinary retention and gastroesophageal reflux disease. Its mechanism involves directly stimulating muscarinic receptors. It has no role in addressing the motor complications like tremors and twitching seen with levodopa/carbidopa in Parkinson's disease. Choice C rationale Amantadine is an antiviral drug also used to treat dyskinesia associated with levodopa therapy in Parkinson's disease. Its precise mechanism of action in Parkinson's is not fully understood, but it is thought to modulate dopaminergic and glutamatergic neurotransmission. It can help reduce tremors, rigidity, and involuntary movements. Choice D rationale Gabapentin is an anticonvulsant and neuropathic pain medication. It is structurally related to GABA but does not act directly on GABA receptors. Its mechanism of action involves modulating calcium channels. While it can treat some neurological symptoms, it is not a primary treatment for levodopa-induced tremors and twitching in Parkinson's disease.