Pharmacology Central Nervous System Agents 2 — Questions and Answers
Question 1: A patient taking an MAO inhibitor eats aged cheese and develops a hypertensive crisis. What interaction caused this?
- Serotonin syndrome from tyramine metabolism
- Tyramine accumulation due to inhibited MAO-A breakdown (Correct answer)
- Direct cheese-drug binding causing vasoconstriction
- Increased dopamine reuptake from tyramine
Correct answer: Tyramine accumulation due to inhibited MAO-A breakdown
MAO-A normally metabolizes dietary tyramine; inhibiting it causes tyramine accumulation, massive norepinephrine release, and hypertensive crisis.
Question 2: Which benzodiazepine is preferred for treating acute alcohol withdrawal seizures due to its long half-life and self-tapering effect?
- Lorazepam
- Midazolam
- Diazepam (Correct answer)
- Alprazolam
Correct answer: Diazepam
Diazepam has active metabolites with very long half-lives, providing a gradual self-tapering effect ideal for alcohol withdrawal management.
Question 3: A patient on lithium presents with coarse tremor, confusion, and ataxia. Serum lithium is 2.8 mEq/L. What is the priority intervention?
- Add propranolol for tremor control
- Discontinue lithium and initiate hemodialysis (Correct answer)
- Reduce lithium dose by half
- Switch to valproate immediately
Correct answer: Discontinue lithium and initiate hemodialysis
Lithium toxicity above 2.5 mEq/L with neurological symptoms requires immediate discontinuation and hemodialysis to rapidly clear lithium.
Question 4: Which mechanism best explains how levodopa reduces Parkinson's symptoms?
- Directly activates dopamine D2 receptors in the striatum
- Crosses the blood-brain barrier and is converted to dopamine (Correct answer)
- Inhibits acetylcholinesterase to restore dopamine-ACh balance
- Blocks COMT enzymes peripherally to increase CNS dopamine
Correct answer: Crosses the blood-brain barrier and is converted to dopamine
Levodopa crosses the blood-brain barrier (unlike dopamine) and is decarboxylated to dopamine by DOPA decarboxylase in the CNS.
Question 5: A nurse administers flumazenil to reverse benzodiazepine sedation. What critical risk must be monitored for?
- Prolonged hypnosis from flumazenil accumulation
- Resedation as flumazenil wears off before the benzodiazepine (Correct answer)
- Acute respiratory alkalosis from rapid arousal
- Hypertensive urgency from sympathetic rebound
Correct answer: Resedation as flumazenil wears off before the benzodiazepine
Flumazenil has a shorter half-life (~1 hour) than most benzodiazepines, so resedation can occur when flumazenil is metabolized.
Question 6: Which antiepileptic drug acts primarily by blocking voltage-gated sodium channels to stabilize neuronal membranes?
- Gabapentin
- Phenytoin (Correct answer)
- Ethosuximide
- Valproic acid
Correct answer: Phenytoin
Phenytoin blocks voltage-gated sodium channels in the inactive state, preventing repetitive neuronal firing without affecting normal neural activity.
Question 7: A patient with bipolar disorder is started on valproate. Which baseline lab is most critical before initiating therapy?
- Serum creatinine and BUN
- Liver function tests (Correct answer)
- Thyroid function tests
- Complete blood count with differential
Correct answer: Liver function tests
Valproate is hepatotoxic (especially in children under 2), so baseline LFTs are essential before initiating therapy.
Pharmacology Central Nervous System Agents 2
A patient taking an MAO inhibitor eats aged cheese and develops a hypertensive crisis.
What interaction caused this?