Central Nervous System Agents Flashcards

A patient stabilized on sertraline for major depressive disorder is prescribed sumatriptan for acute migraine headaches. Shortly after taking both medications, the patient presents to the emergency department with agitation, hyperreflexia, diaphoresis, and a temperature of 39°C. This clinical presentation is most consistent with which adverse drug reaction?

Answer: Serotonin Syndrome

Serotonin syndrome is a potentially life-threatening condition caused by excessive serotonergic activity in the central nervous system. It can occur when two or more serotonergic drugs are used concurrently. Sertraline is a selective serotonin reuptake inhibitor (SSRI), and sumatriptan is a serotonin (5-HT1B/1D) receptor agonist. Their combined use significantly increases the risk of this syndrome, which presents with a triad of autonomic hyperactivity, neuromuscular abnormalities, and mental status changes.

A patient undergoing surgery with sevoflurane and succinylcholine develops sudden tachycardia, muscle rigidity, and a rapid increase in body temperature. Which of the following intravenous agents is the definitive treatment for this life-threatening condition?

Answer: Dantrolene

This patient is experiencing malignant hyperthermia (MH), a rare but severe reaction to volatile anesthetics (like sevoflurane) and depolarizing muscle relaxants (succinylcholine). Dantrolene is the specific antidote for MH. It works by binding to the ryanodine receptor (RyR1) in skeletal muscle, inhibiting the release of calcium from the sarcoplasmic reticulum and thereby resolving the hypermetabolic state and muscle rigidity.

A patient with Parkinson's disease who is managed with levodopa/carbidopa reports that the medication's effects are not lasting until the next scheduled dose, a phenomenon known as 'wearing-off'. To prolong the action of levodopa, a physician adds entacapone to the regimen. What is the mechanism of action of entacapone?

Answer: It inhibits catechol-O-methyltransferase (COMT), reducing peripheral metabolism of levodopa.

Entacapone is a peripheral catechol-O-methyltransferase (COMT) inhibitor. By inhibiting COMT, it prevents the breakdown of levodopa in the periphery, which increases the plasma half-life of levodopa and allows more of it to cross the blood-brain barrier to be converted to dopamine. This leads to more stable dopamine levels in the brain and reduces 'off' time for patients experiencing the 'wearing-off' phenomenon.

Which of the following statements best describes the primary mechanism of action for the anticonvulsant drug phenytoin?

Answer: Blockade of voltage-gated sodium channels

Phenytoin exerts its primary anticonvulsant effect by blocking voltage-gated sodium channels. It stabilizes the channel in its inactivated state, which slows the rate of recovery from inactivation. This action limits the ability of neurons to fire at high frequencies, thus preventing the spread of seizure activity.

A patient brought to the emergency department after a suspected overdose is unconscious with significant respiratory depression. An empty bottle of lorazepam is found at the scene. Which of the following medications should be administered to reverse the effects of the benzodiazepine?

Answer: Flumazenil

Flumazenil is a competitive antagonist at the benzodiazepine binding site on the GABA-A receptor. It competitively displaces benzodiazepines like lorazepam from the receptor, thereby reversing their sedative and respiratory depressant effects. Naloxone is an opioid antagonist, N-acetylcysteine is the antidote for acetaminophen overdose, and protamine sulfate reverses heparin.

Second-generation (atypical) antipsychotics, such as olanzapine and clozapine, generally have a lower risk of causing extrapyramidal symptoms (EPS) compared to first-generation (typical) agents. However, they are more frequently associated with which of the following adverse effects?

Answer: Metabolic syndrome

While second-generation antipsychotics have a lower affinity for D2 receptors, reducing the risk of EPS, many have significant effects on other receptors (e.g., histamine H1, serotonin 5-HT2C) that contribute to a higher risk of metabolic syndrome. This syndrome is characterized by weight gain, dyslipidemia, hyperglycemia, and an increased risk for developing type 2 diabetes.