DAANCE Anesthetic Pharmacology 2 — Questions and Answers
Question 1: Midazolam is preferred over diazepam for IV sedation primarily because it:
- Has a longer duration of action
- Causes superior amnesia and has a shorter half-life (Correct answer)
- Does not cause respiratory depression
- Is reversible with naloxone
Correct answer: Causes superior amnesia and has a shorter half-life
Midazolam produces reliable anterograde amnesia and has a shorter half-life (approximately 2 hours) compared to diazepam (approximately 24 to 48 hours), reducing prolonged sedation.
Midazolam water solubility allows comfortable IV injection. Its rapid onset, superior amnesia, and shorter context-sensitive half-life make it the standard benzodiazepine for dental IV sedation. Diazepam long half-life increases residual sedation and fall risk.
Question 2: Flumazenil (Romazicon) reverses benzodiazepine sedation by:
- Stimulating endorphin release in the CNS
- Competitively blocking GABA-A receptor benzodiazepine sites (Correct answer)
- Inhibiting serotonin reuptake
- Activating mu-opioid receptors
Correct answer: Competitively blocking GABA-A receptor benzodiazepine sites
Flumazenil competitively antagonizes benzodiazepines at the GABA-A receptor benzodiazepine binding site, reversing sedation without affecting opioid effects.
Flumazenil mechanism is pure competitive antagonism at the benzodiazepine site on the GABA-A receptor. Its short half-life (approximately 1 hour) means resedation can occur if a long-acting benzodiazepine was used, requiring monitoring for at least 2 hours after administration.
Question 3: Which opioid is most commonly used for IV conscious sedation in the dental office due to its rapid onset and short duration?
- Morphine
- Meperidine (Demerol)
- Fentanyl (Correct answer)
- Codeine
Correct answer: Fentanyl
Fentanyl has an onset of approximately 2 minutes and peak effect at 5 minutes with a short duration (approximately 30 to 60 min), making it ideal for procedural sedation.
Fentanyl is 100 times more potent than morphine and is highly lipophilic, producing rapid CNS penetration. Its short duration results from redistribution rather than metabolism. These pharmacokinetic properties allow precise titration during dental procedures.
Question 4: Nitrous oxide exerts its clinical effects primarily through:
- GABA-A receptor potentiation only
- NMDA receptor antagonism and endogenous opioid release (Correct answer)
- Alpha-2 adrenergic receptor agonism
- Muscarinic acetylcholine receptor blockade
Correct answer: NMDA receptor antagonism and endogenous opioid release
Nitrous oxide anxiolytic and analgesic effects are mediated largely by NMDA antagonism and endogenous opioid system activation.
Unlike benzodiazepines and barbiturates (GABA-A agonists), nitrous oxide primarily blocks NMDA receptors and stimulates the release of endogenous opioid peptides. It also has weak GABA-A potentiating activity. This multi-modal mechanism explains its combined anxiolytic, analgesic, and amnestic properties.
Question 5: A patient receiving IV ketamine for sedation is most likely to exhibit which distinctive clinical finding?
- Deep unconsciousness with absent reflexes
- Dissociative anesthesia with preserved airway reflexes (Correct answer)
- Respiratory depression requiring assisted ventilation
- Profound bradycardia and hypotension
Correct answer: Dissociative anesthesia with preserved airway reflexes
Ketamine produces a dissociative state where the patient appears awake but is unresponsive to pain, while maintaining airway tone and protective reflexes.
Ketamine (NMDA antagonist) produces dissociative anesthesia characterized by catalepsy, profound analgesia, and amnesia while airway reflexes are preserved. It also causes sympathomimetic stimulation (increased BP and HR). Emergence reactions can be attenuated by co-administration of a benzodiazepine.
Question 6: The maximum recommended dose of epinephrine in a local anesthetic for a healthy adult per appointment is:
- 0.04 mg (40 mcg)
- 0.2 mg (200 mcg) (Correct answer)
- 1.0 mg (1000 mcg)
- 2.0 mg (2000 mcg)
Correct answer: 0.2 mg (200 mcg)
The maximum epinephrine dose for a healthy adult is 0.2 mg (200 mcg) per appointment to avoid cardiovascular adverse effects.
ADA and manufacturer guidelines limit epinephrine to 0.2 mg in healthy adults. For cardiac patients the limit is lower (0.04 mg). Each 1.8 mL carpule of 1:100,000 epinephrine contains 0.018 mg, so approximately 11 carpules equals the healthy adult maximum.
DAANCE Anesthetic Pharmacology 2
Midazolam is preferred over diazepam for IV sedation primarily because it: