USMLE Step 1 Quiz: Central Nervous System Pharmacology

Hypertensive crisis after MAO inhibitor and aged cheese is caused by:

Nephrolithiasis during topiramate therapy results from:

Tremor and rigidity from haloperidol are due to:

Osteomalacia during chronic phenytoin therapy is most directly due to:

Chronic levodopa therapy causes dyskinesias mainly because of:

A 45-year-old man with a long history of schizophrenia, previously managed with haloperidol, is switched to a new medication due to persistent negative symptoms. Six months later, his fasting glucose is 135 mg/dL and he has gained 11 kg (25 lb). His psychotic symptoms, however, have improved. The new medication is discontinued due to these metabolic changes.

The beneficial effects and metabolic side effects of this new medication are most likely mediated by its antagonist activity at which combination of receptors?

A 55-year-old woman being treated for atypical depression with phenelzine is brought to the emergency department with a severe headache, palpitations, and a blood pressure of 210/120 mm Hg. She reports that her symptoms began shortly after attending a wine and cheese party. She has been compliant with her medication regimen.

This patient's hypertensive crisis is a result of the prescribed medication inhibiting an enzyme that normally metabolizes which of the following substances found in the consumed food and beverage?

An 82-year-old woman with generalized anxiety disorder is prescribed a low dose of lorazepam. A week later, her daughter brings her to the clinic because she has become increasingly confused, forgetful, and has had two falls. The physician suspects the new medication is responsible for these symptoms.

This medication exerts its anxiolytic and adverse cognitive effects by which of the following mechanisms?

A 34-year-old man undergoes an open reduction and internal fixation of a tibial fracture. Postoperatively, he is started on a patient-controlled analgesia pump with morphine. While his pain is well-controlled, he complains of significant constipation by the second postoperative day. He has no prior history of gastrointestinal issues.

This common adverse effect of morphine is primarily mediated by the activation of which receptors in the enteric nervous system?

A 68-year-old man with Parkinson disease is treated with a combination of levodopa and carbidopa. His bradykinesia and rigidity improve significantly. He experiences mild nausea but avoids the severe vomiting and cardiac arrhythmias that can occur with levodopa alone.

What is the primary mechanism by which carbidopa enhances the therapeutic effect of levodopa and reduces its peripheral side effects?

A 22-year-old man with a history of generalized tonic-clonic seizures is being managed with an antiepileptic drug. During a routine dental visit, the dentist notes significant gingival hyperplasia. The patient also mentions that he has noticed increased growth of coarse hair on his face and trunk.

The medication responsible for these findings most likely exerts its anticonvulsant effect by which of the following mechanisms?

A 28-year-old man is started on sertraline for major depressive disorder. After six weeks of treatment, his mood has improved significantly, but he reports new-onset difficulty achieving orgasm, which he finds distressing. He has no other medical problems and takes no other medications.

This adverse effect is a well-known complication of medications that increase the synaptic concentration of which neurotransmitter?

A 30-year-old woman is undergoing a brief surgical procedure for which desflurane, an inhaled anesthetic, is used. The anesthesiologist notes that both the induction of and emergence from anesthesia are very rapid. The patient is awake and alert shortly after the anesthetic is discontinued.

The rapid onset and recovery associated with this anesthetic agent are best explained by which of its physicochemical properties?

A 35-year-old man with acute psychosis is started on haloperidol. Within a week, he develops a slow, shuffling gait, a resting tremor in his right hand, and a noticeable lack of facial expression. His wife states he seems 'stiff as a board.'

These extrapyramidal symptoms are a direct consequence of haloperidol's antagonist activity at which of the following receptors in the nigrostriatal pathway?

A 9-year-old boy is diagnosed with attention-deficit/hyperactivity disorder (ADHD). He is started on methylphenidate. After several weeks, his parents and teacher report a significant improvement in his ability to focus on tasks and a reduction in hyperactive and impulsive behaviors.

What is the primary mechanism of action of methylphenidate in treating ADHD?

A dentist injects lidocaine, a local anesthetic, to numb a patient's gum before a procedure. However, the injection is administered into an area of inflamed, abscessed tissue. The patient reports that the anesthetic effect is much weaker than expected.

The reduced efficacy of the local anesthetic in this setting is best explained by which of the following?

An 80-year-old man with postherpetic neuralgia is prescribed low-dose amitriptyline. While it helps his pain, he complains of a persistently dry mouth, difficulty urinating, and constipation. On examination, his pupils are noted to be dilated.

These adverse effects are caused by the drug's antagonist activity at which of the following receptors?

A 27-year-old woman with epilepsy is well-controlled on valproic acid. She and her partner are planning a pregnancy and she consults her neurologist for preconception counseling. The physician discusses the significant teratogenic risks associated with her current medication.

In utero exposure to valproic acid is most strongly associated with an increased risk for which of the following congenital malformations?

A 75-year-old woman is diagnosed with mild Alzheimer disease after her family notes progressive memory loss over the past year. She is started on donepezil. Her family is counseled that the medication may offer a modest, temporary improvement in cognitive function.

This medication aims to improve cognitive symptoms by increasing the synaptic availability of which neurotransmitter?

A 48-year-old man with bipolar I disorder has been maintained on lithium for several years. He presents to his physician complaining of constant thirst, frequent urination, and a persistent fine tremor in his hands. Laboratory studies show a normal serum glucose and a serum sodium of 143 mEq/L. His lithium level is within the therapeutic range.

Lithium is thought to produce both its therapeutic and certain adverse effects, such as nephrogenic diabetes insipidus, by interfering with which of the following signaling pathways?