CNS Pharmacology Basics 5 — Questions and Answers
Question 1: A patient taking an SSRI is started on linezolid and develops agitation, hyperthermia, and clonus. What is the most likely diagnosis?
- Neuroleptic malignant syndrome
- Serotonin syndrome (Correct answer)
- Malignant hyperthermia
- Anticholinergic toxicity
Correct answer: Serotonin syndrome
Linezolid is a weak MAO inhibitor, and combination with SSRIs can cause serotonin syndrome marked by clonus and hyperreflexia.
Question 2: Which feature best distinguishes neuroleptic malignant syndrome from serotonin syndrome?
- Fever
- Altered mental status
- Lead-pipe rigidity with bradyreflexia and slower onset (Correct answer)
- Tachycardia
Correct answer: Lead-pipe rigidity with bradyreflexia and slower onset
NMS develops over days with lead-pipe rigidity and decreased reflexes, while serotonin syndrome is rapid with hyperreflexia and clonus.
Question 3: What is the recommended first-line medication class for an actively seizing patient in status epilepticus?
- Benzodiazepines (Correct answer)
- Barbiturates
- Propofol
- Levetiracetam
Correct answer: Benzodiazepines
IV lorazepam, IM midazolam, or IV diazepam is first-line for status epilepticus per established guidelines.
Question 4: When administering IV phenytoin, which precaution is most important?
- Mix with dextrose 5% in water
- Give as a rapid IV push
- Administer only via intramuscular route
- Infuse no faster than 50 mg/min with cardiac monitoring (Correct answer)
Correct answer: Infuse no faster than 50 mg/min with cardiac monitoring
Rapid phenytoin infusion can cause hypotension and arrhythmias, so rate is limited and it is mixed in normal saline.
Question 5: Fosphenytoin offers which advantage over IV phenytoin?
- It does not require conversion to phenytoin
- Lower risk of infusion-site injury such as purple glove syndrome (Correct answer)
- It has no cardiovascular effects
- It is not monitored by serum levels
Correct answer: Lower risk of infusion-site injury such as purple glove syndrome
Fosphenytoin is a water-soluble prodrug that causes less tissue injury and can be infused faster, dosed in phenytoin equivalents.
Question 6: Hyponatremia is a well-known adverse effect of which antiseizure medication?
- Oxcarbazepine (Correct answer)
- Levetiracetam
- Lacosamide
- Gabapentin
Correct answer: Oxcarbazepine
Oxcarbazepine, and to a lesser degree carbamazepine, can cause SIADH-like hyponatremia, so sodium should be monitored.
Question 7: Which laboratory monitoring is most important for a patient starting valproic acid?
- Serum potassium and magnesium
- Thyroid function tests
- Liver function tests and platelet count (Correct answer)
- Serum lithium level
Correct answer: Liver function tests and platelet count
Valproate carries risks of hepatotoxicity and thrombocytopenia, requiring LFT and platelet monitoring.
CNS Pharmacology Basics 5
A patient taking an SSRI is started on linezolid and develops agitation, hyperthermia, and clonus.
What is the most likely diagnosis?