Pharmacology · patient case question
What is the mechanism of action of carbamazepine?
Patient case: Alzheimer Disease and Consent for Care
Patient: 72-year-old male
Chief Complaint: Daughter: “He won’t let anyone near his mouth and I think his teeth are getting worse.”
Background: Moderate Alzheimer disease diagnosed 4 years ago. Trigeminal neuralgia on the right, managed medically. Disoriented to time and place; cannot reliably recall the purpose of today’s visit. His daughter holds a durable power of attorney for health care.
Medications: Donepezil 10 mg daily · Carbamazepine 200 mg twice daily
Vital Signs: BP 144/82 mmHg · HR 72 bpm · RR 16 · T 98.2°F
Findings: Generalized plaque accumulation, multiple root caries, and moderate periodontitis. Multiple restorations required. He is calm but does not follow multi-step instructions.
Show answer and explanation
Correct answer: A. Blocks voltage-gated sodium channels
- A. Correct. Carbamazepine stabilizes inactivated voltage-gated sodium channels, reducing neuronal firing (used for seizures and trigeminal neuralgia).
- B. GABA-A potentiation describes benzodiazepines/barbiturates.
- C. Calcium-channel blockade describes ethosuximide (T-type) or cardiac CCBs, not carbamazepine's primary action.
- D. Glutamate modulation is not carbamazepine's main mechanism.
Note: Dental relevance: carbamazepine is a potent inducer of hepatic CYP3A4, so it accelerates metabolism of many co-prescribed drugs. It can also cause leukopenia, agranulocytosis, and hyponatremia, which makes a recent complete blood count worth reviewing before surgery.