NDEB - National Dental Examining Board Dental Pharmacology and Therapeutics Questions and Answers — Questions and Answers
Question 1: A 58-year-old male patient with a history of a prosthetic heart valve replacement 2 years ago requires a surgical extraction of a non-restorable tooth. The patient has a documented allergy to penicillin, which manifests as anaphylaxis. According to the most current Canadian guidelines for infective endocarditis prophylaxis, which of the following is the most appropriate antibiotic to prescribe?
- Cephalexin 2g orally, 1 hour before the procedure
- No antibiotic prophylaxis is required
- Clindamycin 600mg orally, 1 hour before the procedure (Correct answer)
- Amoxicillin 2g orally, 1 hour before the procedure
Correct answer: Clindamycin 600mg orally, 1 hour before the procedure
For patients with high-risk cardiac conditions, such as a prosthetic heart valve, who are undergoing a dental procedure involving manipulation of gingival tissue, antibiotic prophylaxis is recommended. Since this patient has a history of an anaphylactic reaction to penicillin, cephalosporins should also be avoided due to potential cross-reactivity. Therefore, Clindamycin 600mg orally is the recommended alternative prophylactic agent. Amoxicillin is contraindicated due to the severe allergy.
Question 2: A 45-year-old patient presents for a dental appointment and reports taking a tricyclic antidepressant (TCA), amitriptyline. Which of the following is the most significant consideration when administering a local anesthetic with a vasoconstrictor to this patient?
- Increased risk of methemoglobinemia
- Decreased duration of the local anesthetic effect
- Potentiated pressor effect of the vasoconstrictor (Correct answer)
- Higher likelihood of an allergic reaction to the anesthetic
Correct answer: Potentiated pressor effect of the vasoconstrictor
Tricyclic antidepressants (TCAs) can block the reuptake of norepinephrine at nerve terminals. When a local anesthetic containing a sympathomimetic vasoconstrictor like epinephrine or levonordefrin is administered, the pressor effect (increase in blood pressure) can be significantly potentiated, potentially leading to a hypertensive crisis. Therefore, the dose of the vasoconstrictor should be limited. The other options are not the primary concern associated with this specific drug interaction.
Question 3: Which of the following is the most common adverse effect associated with the long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen for managing chronic dental pain?
- Hepatotoxicity
- Gastrointestinal toxicity (Correct answer)
- Respiratory depression
- Addiction and dependence
Correct answer: Gastrointestinal toxicity
The most frequent and well-documented adverse effects of long-term NSAID use are related to the gastrointestinal (GI) system. NSAIDs inhibit prostaglandins that are protective of the gastric mucosa, which can lead to dyspepsia, mucosal erosion, and ulceration. While hepatotoxicity can occur with acetaminophen and respiratory depression and addiction are concerns with opioids, GI toxicity is the hallmark adverse effect of chronic NSAID therapy.
Question 4: A patient undergoing a routine dental cleaning suddenly becomes pale, diaphoretic, and reports feeling lightheaded. They then lose consciousness. You place the patient in a supine position with their legs slightly elevated. Which of the following is the most likely diagnosis and the immediate next step in management?
- Anaphylaxis; administer intramuscular epinephrine
- Hypoglycemia; administer oral glucose
- Myocardial infarction; administer sublingual nitroglycerin
- Vasovagal syncope; administer oxygen and monitor vital signs (Correct answer)
Correct answer: Vasovagal syncope; administer oxygen and monitor vital signs
The signs and symptoms described (pallor, diaphoresis, lightheadedness, loss of consciousness) are classic for vasovagal syncope, the most common medical emergency in a dental office. The initial management is to position the patient to improve cerebral blood flow (supine with legs elevated). The next immediate steps are to ensure a patent airway and administer oxygen while monitoring vital signs. The other options are less likely given the typical presentation in a dental setting without other specific signs.
Question 5: A dentist prescribes amoxicillin for a patient with a dental abscess. The patient is also taking an oral contraceptive. What is the most crucial counseling point the dentist must provide regarding this drug combination?
- The amoxicillin will cause severe hypertension when taken with the contraceptive.
- The oral contraceptive will inactivate the amoxicillin, leading to treatment failure.
- The amoxicillin may decrease the efficacy of the oral contraceptive, and a backup method of birth control should be used. (Correct answer)
- The combination increases the risk of developing a severe photosensitivity reaction.
Correct answer: The amoxicillin may decrease the efficacy of the oral contraceptive, and a backup method of birth control should be used.
Certain antibiotics, including broad-spectrum penicillins like amoxicillin, can potentially reduce the effectiveness of oral contraceptives. This is thought to occur by altering the gut flora, which interferes with the enterohepatic circulation and reabsorption of contraceptive hormones. Therefore, it is essential to advise the patient to use an additional, non-hormonal (barrier) method of contraception during the course of antibiotic therapy and for a short period afterward to prevent unintended pregnancy.
Question 6: A patient with a known allergy to ester-type local anesthetics requires a maxillary infiltration for a restorative procedure. Which of the following local anesthetic agents would be the safest to use?
- Procaine
- Benzocaine (topical)
- Lidocaine (Correct answer)
- Tetracaine
Correct answer: Lidocaine
Lidocaine is an amide-type local anesthetic. Allergies to local anesthetics are more common with the ester class due to their metabolism to para-aminobenzoic acid (PABA). A true allergy to one ester-type anesthetic generally contraindicates the use of all other ester anesthetics (like procaine and tetracaine). While benzocaine is an ester, an allergy to one amide does not rule out the use of another amide, making lidocaine a safe choice in this scenario.
