DDS Dental Pharmacology and Anesthesia 1 — Questions and Answers
Question 1: The maximum recommended dose of lidocaine with epinephrine (1:100,000) for a healthy 70 kg adult dental patient is approximately:
- 200 mg (≈5.5 carpules)
- 500 mg (≈13.9 carpules) (Correct answer)
- 100 mg (≈2.7 carpules)
- 700 mg (≈19.4 carpules)
Correct answer: 500 mg (≈13.9 carpules)
The MRD of lidocaine with vasoconstrictor is 7 mg/kg, giving approximately 500 mg (about 13–14 carpules of 1.8 mL 2% lidocaine) for a 70 kg patient.
Question 2: Which local anesthetic has the longest duration of action for dental pulp anesthesia?
- Lidocaine
- Prilocaine
- Bupivacaine (Correct answer)
- Mepivacaine
Correct answer: Bupivacaine
Bupivacaine (Marcaine) provides the longest duration of pulpal anesthesia (up to 5–7 hours) due to its high lipid solubility and protein binding.
Question 3: Methemoglobinemia is a specific adverse effect associated with which local anesthetic?
- Lidocaine
- Bupivacaine
- Prilocaine (Correct answer)
- Articaine
Correct answer: Prilocaine
Prilocaine metabolism produces ortho-toluidine, which oxidizes hemoglobin iron to the ferric state, causing methemoglobinemia at high doses.
Question 4: Epinephrine in local anesthetic cartridges acts by:
- Directly blocking sodium channels to enhance anesthesia depth
- Causing local vasoconstriction to slow systemic absorption and prolong anesthesia (Correct answer)
- Raising the pH of the solution to increase un-ionized free base form
- Inhibiting prostaglandin synthesis at the injection site
Correct answer: Causing local vasoconstriction to slow systemic absorption and prolong anesthesia
Epinephrine binds alpha-1 adrenoceptors causing vasoconstriction, reducing vascular absorption of the local anesthetic and thereby prolonging its duration and reducing toxicity risk.
Question 5: The pKa of lidocaine is approximately 7.9. In an infected (acidic) tissue environment, anesthesia is difficult because:
- More of the drug is in the ionized (charged) form, which cannot penetrate the nerve membrane (Correct answer)
- Infection destroys the drug before it can act
- The pH rise increases vasoconstriction and limits drug delivery
- Acidic tissue accelerates myelination of nerve fibers
Correct answer: More of the drug is in the ionized (charged) form, which cannot penetrate the nerve membrane
At lower pH (acidic infection), the equilibrium shifts toward the ionized (protonated, BH+) form of the local anesthetic, which cannot penetrate lipid nerve membranes to reach the sodium channel.
Question 6: Which drug is used to reverse soft tissue anesthesia after dental procedures by antagonizing epinephrine's vasoconstriction?
- Naloxone
- Flumazenil
- Phentolamine mesylate (OraVerse) (Correct answer)
- Atropine
Correct answer: Phentolamine mesylate (OraVerse)
Phentolamine mesylate (OraVerse) is an alpha-adrenergic antagonist injected after dental procedures to reverse epinephrine-mediated vasoconstriction and accelerate return of normal sensation.
DDS Dental Pharmacology and Anesthesia 1
The maximum recommended dose of lidocaine with epinephrine (1:100,000) for a healthy 70 kg adult dental patient is approximately: