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Pharmacology · patient case with 3 questions

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.

Question 1

For which condition is donepezil prescribed, and by what mechanism does it act?

  1. Alzheimer disease — it inhibits acetylcholinesterase
  2. Major depressive disorder — it inhibits serotonin reuptake
  3. Parkinson disease — it is a dopamine precursor
  4. Epilepsy — it enhances GABAergic inhibition
Show answer and explanation

Correct answer: A. Alzheimer disease — it inhibits acetylcholinesterase

  • A. Correct. Donepezil is a centrally acting, reversible acetylcholinesterase inhibitor. By slowing the breakdown of acetylcholine it partially compensates for the cholinergic deficit of Alzheimer disease, producing modest symptomatic benefit without altering the underlying course.
  • B. Incorrect. Serotonin reuptake inhibition describes the SSRI class, such as sertraline and fluoxetine.
  • C. Incorrect. Levodopa combined with carbidopa is the dopamine precursor therapy for Parkinson disease. Donepezil has no dopaminergic action.
  • D. Incorrect. Enhancement of GABAergic inhibition describes benzodiazepines, barbiturates, and several antiepileptics. Donepezil is not an anticonvulsant.

Note: Class members worth knowing: donepezil, rivastigmine, and galantamine are the cholinesterase inhibitors. Memantine works differently, as an NMDA receptor antagonist, and is used in moderate to severe disease.

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Question 2

What is the most appropriate next step in managing this patient?

  1. Obtain a medical consultation from his physician before initiating treatment
  2. Instruct his daughter to give him three doses of a benzodiazepine one hour before the appointment
  3. Sedate him without consent, since he cannot consent for himself
  4. Proceed with treatment without any modification to the plan
Show answer and explanation

Correct answer: A. Obtain a medical consultation from his physician before initiating treatment

  • A. Correct. A medical consultation establishes the stage of his disease, his current medication regimen and interactions, his capacity, and whether any sedation is safe. It also formalizes communication with the physician managing his overall care and informs realistic treatment planning.
  • B. Incorrect. This is unsafe on several counts: it is an unmonitored dose given by an untrained person outside the office, three doses of any benzodiazepine is a serious overdose risk in an elderly patient, and it invites respiratory depression with no one present to intervene.
  • C. Incorrect. Treating without consent is battery. When a patient lacks capacity, consent must be obtained from the person holding legal authority — here, the daughter with durable power of attorney.
  • D. Incorrect. A patient who cannot follow multi-step instructions and resists intraoral access requires a modified approach. Proceeding unchanged ignores both his safety and the likelihood of a poor outcome.

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Question 3

What is the mechanism of action of carbamazepine?

  1. Blocks voltage-gated sodium channels
  2. Enhances GABA-A chloride channels
  3. Blocks calcium channels
  4. Inhibits glutamate release only
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.

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