NBDE Pharmacology and Therapeutics 5 — Questions and Answers
Question 1: Which alpha-2 adrenergic agonist is used as an adjunct for sedation in dentistry and can cause rebound hypertension upon abrupt withdrawal?
- Prazosin
- Clonidine (Correct answer)
- Phentolamine
- Doxazosin
Correct answer: Clonidine
Clonidine acts centrally on alpha-2 receptors to reduce sympathetic outflow; abrupt withdrawal causes rebound hypertension due to sympathetic surge.
Question 2: A patient taking SSRIs (e.g., fluoxetine) is prescribed tramadol for postoperative pain. The PRIMARY concern with this combination is:
- Increased sedation from synergistic CNS depression
- Serotonin syndrome due to excess serotonergic activity (Correct answer)
- Reduced tramadol efficacy from CYP2D6 inhibition
- Hypertensive crisis from norepinephrine potentiation
Correct answer: Serotonin syndrome due to excess serotonergic activity
Both SSRIs and tramadol increase serotonergic transmission; combining them raises the risk of serotonin syndrome (agitation, hyperthermia, clonus).
Question 3: Which property of a local anesthetic MOST determines its duration of action?
- pKa
- Degree of protein binding (Correct answer)
- Lipid solubility
- Molecular weight
Correct answer: Degree of protein binding
Local anesthetics with higher protein binding (e.g., bupivacaine at ~95%) remain bound to sodium channel proteins longer, extending their duration of action.
Question 4: Vasopressin (felypressin) is used as a vasoconstrictor with prilocaine. Compared to epinephrine, it is PREFERRED in patients with:
- Renal failure requiring dialysis
- Severe cardiovascular disease or thyrotoxicosis (Correct answer)
- Uncontrolled type 2 diabetes mellitus
- Severe hepatic cirrhosis
Correct answer: Severe cardiovascular disease or thyrotoxicosis
Felypressin acts on V1 receptors without beta-adrenergic stimulation, making it safer in patients with ischemic heart disease or hyperthyroidism.
Question 5: Which drug is used to treat acute narrow-angle glaucoma that can be precipitated by anticholinergic premedications given in dentistry?
- Timolol eye drops
- Pilocarpine eye drops (Correct answer)
- Atropine IV
- Tropicamide eye drops
Correct answer: Pilocarpine eye drops
Pilocarpine, a cholinergic miotic, reverses pupillary dilation and reduces intraocular pressure in acute angle-closure glaucoma.
Question 6: Epinephrine is included in local anesthetic solutions primarily to:
- Reduce systemic absorption and prolong anesthetic duration (Correct answer)
- Increase the pKa of the anesthetic for faster onset
- Prevent allergic reactions to the anesthetic
- Directly produce analgesia by binding opioid receptors
Correct answer: Reduce systemic absorption and prolong anesthetic duration
Epinephrine causes local vasoconstriction, slowing systemic absorption of the anesthetic, which prolongs duration and reduces peak plasma toxicity.
Question 7: A patient undergoing IV sedation receives too much midazolam and becomes apneic. After airway management, which reversal agent should be administered?
- Naloxone 0.4 mg IV
- Flumazenil 0.2 mg IV titrated (Correct answer)
- Physostigmine 1 mg IV
- Sugammadex 200 mg IV
Correct answer: Flumazenil 0.2 mg IV titrated
Flumazenil competitively reverses benzodiazepine-induced sedation and respiratory depression; it is titrated in 0.2 mg increments to avoid resedation.
NBDE Pharmacology and Therapeutics 5
Which alpha-2 adrenergic agonist is used as an adjunct for sedation in dentistry and can cause rebound hypertension upon abrupt withdrawal?