DAANCE Pharmacology 5 — Questions and Answers
Question 1: A patient is taking a monoamine oxidase inhibitor (MAOI). Which sedation-related drug combination poses the greatest risk of a life-threatening interaction?
- Nitrous oxide and oxygen
- Meperidine and an MAOI (Correct answer)
- Midazolam and flumazenil
- Lidocaine and epinephrine
Correct answer: Meperidine and an MAOI
Meperidine combined with MAOIs can cause a serotonin syndrome or excitatory reaction that may be fatal; this combination is absolutely contraindicated.
Question 2: Which property of nitrous oxide makes it unsuitable for prolonged use (>6 hours) or use in patients with vitamin B12 deficiency?
- It irreversibly inhibits methionine synthase (Correct answer)
- It displaces oxygen from hemoglobin
- It activates NMDA receptors excessively
- It inhibits hepatic cytochrome P450 enzymes
Correct answer: It irreversibly inhibits methionine synthase
Nitrous oxide irreversibly oxidizes the cobalt atom in vitamin B12, inhibiting methionine synthase and impairing DNA synthesis, which is especially harmful with prolonged exposure.
Question 3: The vasopressor of choice for treating hypotension caused by anaphylaxis during dental sedation is:
- Norepinephrine IV push
- Epinephrine 1:1,000 IM (Correct answer)
- Dopamine infusion
- Phenylephrine IV
Correct answer: Epinephrine 1:1,000 IM
Epinephrine 1:1,000 (0.3-0.5 mg) administered IM into the lateral thigh is the first-line treatment for anaphylaxis due to its rapid bronchodilatory and vasopressor effects.
Question 4: Propofol's rapid emergence from sedation is primarily due to which pharmacokinetic property?
- Rapid renal excretion of unchanged drug
- High lipid solubility enabling rapid redistribution (Correct answer)
- Short elimination half-life of 15 minutes
- Active hepatic metabolism to a stimulant metabolite
Correct answer: High lipid solubility enabling rapid redistribution
Propofol's high lipid solubility allows rapid redistribution from the brain to peripheral tissues, explaining the quick recovery even though its terminal half-life is several hours.
Question 5: Which of the following describes the mechanism of action of succinylcholine (a depolarizing neuromuscular blocker)?
- Competitively blocks acetylcholine at nicotinic receptors without activating them
- Binds and activates nicotinic receptors, causing persistent depolarization (Correct answer)
- Inhibits acetylcholinesterase, increasing synaptic acetylcholine levels
- Blocks voltage-gated sodium channels at the motor end plate
Correct answer: Binds and activates nicotinic receptors, causing persistent depolarization
Succinylcholine mimics acetylcholine at nicotinic receptors, causing depolarization and initial fasciculations, then sustained depolarization prevents repolarization and produces flaccid paralysis.
Question 6: A patient on chronic opioid therapy requires IV sedation. Compared to an opioid-naive patient, this patient will likely need:
- Lower doses of opioids due to receptor sensitization
- Higher doses of opioids due to tolerance, but same benzodiazepine doses (Correct answer)
- Standard doses because tolerance affects only oral routes
- No opioids; switch entirely to ketamine
Correct answer: Higher doses of opioids due to tolerance, but same benzodiazepine doses
Chronic opioid use leads to pharmacodynamic tolerance at mu receptors, requiring higher opioid doses for the same effect, while benzodiazepine requirements are generally unchanged.
Question 7: Which statement about atropine use in dental anesthesia is CORRECT?
- It is used to treat tachycardia caused by epinephrine overdose
- It reduces secretions and treats bradycardia by blocking muscarinic receptors (Correct answer)
- It reverses benzodiazepine-induced sedation within 5 minutes
- It is contraindicated in all patients with a history of heart disease
Correct answer: It reduces secretions and treats bradycardia by blocking muscarinic receptors
Atropine is an anticholinergic (antimuscarinic) agent that reduces salivary and airway secretions and increases heart rate, making it useful for treating sedation-related bradycardia.
DAANCE Pharmacology 5
A patient is taking a monoamine oxidase inhibitor (MAOI).
Which sedation-related drug combination poses the greatest risk of a life-threatening interaction?