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How drugs work and how to prescribe · Pharmacology · INBDE Patient Cases

Principles of Pharmacology INBDE Patient Cases

By Dr. Isaac Sun, DDS

7 ADA INBDE-format patient cases on principles of pharmacology. Each case is a shared patient box (chief complaint, history, medications, allergies, exam) followed by linked multiple-choice questions with full distractor explanations. Practice the way the real exam is structured.

7 patient cases35 linked questionsADA INBDE formatFull distractor explanations

Seven ADA INBDE-format patient cases on principles of pharmacology: sublingual nitroglycerin bypassing first-pass metabolism, an antibiotic raising the INR in a warfarin patient through CYP inhibition and gut-flora effects, codeine variability from CYP2D6 polymorphism (poor vs ultra-rapid metabolizers) and the ibuprofen-acetaminophen alternative, naloxone as a competitive opioid antagonist that may need redosing, warfarin as a narrow therapeutic index drug requiring INR monitoring, acetaminophen hepatotoxicity from NAPQI and the N-acetylcysteine antidote, and writing a safe dental prescription with complete elements and review of the medication list. Topics include pharmacokinetics, pharmacodynamics, CYP450 inducers and inhibitors, agonism and antagonism, therapeutic index, drug interactions, and prescribing principles.

Case Coverage Map
What each case is testing
Why the nitroglycerin goes under the tongue:
First-pass metabolism, sublingual bypass, bioavailability of intravenous vs oral, and why oral nitroglycerin would barely work.
An antibiotic that runs up the INR:
Warfarin-antibiotic interaction through CYP inhibition and gut-flora effects, the inducer contrast, and narrow therapeutic index.
When the same dose works differently:
Codeine as a CYP2D6 prodrug, poor and ultra-rapid metabolizer effects, pharmacogenetic variability, and the non-opioid alternative.
Reversing an opioid with naloxone:
Naloxone as a competitive antagonist that can be overcome, the short-half-life re-sedation caveat, and the competitive vs non-competitive distinction.
Why warfarin needs INR monitoring:
Narrow therapeutic index, TI definition, other narrow-TI drugs, and the practical implication of monitoring and not routinely stopping warfarin.
Hepatotoxicity from too much acetaminophen:
NAPQI metabolite, glutathione depletion, N-acetylcysteine antidote, chronic ethanol risk, and that OTC drugs still have dose limits.
Writing a safe dental prescription:
Required prescription elements, the ibuprofen-acetaminophen combination, dose adjustments for elderly and organ impairment, sig abbreviations, and reviewing the medication list.
Patient case: Why the nitroglycerin goes under the tongue
0 of 5 answered, 0 correct
Patient
Male, 62 years old
Chief Complaint
Develops chest pain during a procedure; takes sublingual nitroglycerin as needed.
Background and/or Patient History
  • History of stable angina; carries sublingual nitroglycerin
  • Question of why the drug is given under the tongue rather than swallowed
  • Otherwise stable
Allergies
NKDA
Medications
  • Sublingual nitroglycerin (PRN)
Current Findings
  • Angina patient requiring sublingual nitroglycerin
  • Discussion of route choice and first-pass metabolism
  1. Question 1
    Moderate
    Nitroglycerin is given sublingually rather than orally because:
  2. Question 2
    Moderate
    First-pass metabolism occurs when:
  3. Question 3
    Moderate
    Routes that bypass first-pass metabolism include:
  4. Question 4
    Moderate
    Bioavailability is highest with which route?
  5. Question 5
    Moderate
    If the patient instead took an oral nitroglycerin tablet, what would you predict?

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Patient case: An antibiotic that runs up the INR
0 of 5 answered, 0 correct
Patient
Female, 71 years old
Chief Complaint
Developed bleeding gums and bruising after starting an antibiotic; takes warfarin.
Background and/or Patient History
  • On warfarin for atrial fibrillation; INR usually well controlled
  • Started metronidazole for a dental infection
  • Now notes easy bruising and gum bleeding
Allergies
NKDA
Medications
  • Warfarin
  • Metronidazole (recent)
Current Findings
  • Possible warfarin-antibiotic interaction with elevated INR
  • Bleeding signs
  1. Question 1
    Moderate
    The most likely cause of the new bleeding is:
  2. Question 2
    Hard
    The mechanism is a pharmacokinetic interaction in which:
  3. Question 3
    Moderate
    This kind of pharmacokinetic interaction is described as:
  4. Question 4
    Hard
    An example of a CYP inducer that would have the OPPOSITE effect on warfarin (lowering the INR) is:
  5. Question 5
    Moderate
    Because warfarin has a narrow therapeutic index, the practical implication is:

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Patient case: When the same dose works differently
0 of 5 answered, 0 correct
Patient
Mixed (case presentation)
Chief Complaint
Variable analgesia and toxicity reports after the same codeine dose.
Background and/or Patient History
  • Codeine is widely prescribed for postoperative dental pain
  • Some patients report no pain relief; others have unexpected sedation or respiratory issues
  • Genetic variation in metabolism explains much of the difference
Allergies
NKDA
Medications
  • Codeine
Current Findings
  • Variable codeine response across patients
  • CYP2D6 polymorphism being discussed
  1. Question 1
    Moderate
    Codeine is a prodrug that requires activation by:
  2. Question 2
    Hard
    A 'poor metabolizer' at CYP2D6 will:
  3. Question 3
    Hard
    An 'ultra-rapid metabolizer' at CYP2D6 will:
  4. Question 4
    Moderate
    This variability is an example of:
  5. Question 5
    Moderate
    Clinically, this is one reason that:

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Patient case: Reversing an opioid with naloxone
0 of 5 answered, 0 correct
Patient
Male, 30 years old
Chief Complaint
Respiratory depression after a high opioid exposure; naloxone is administered.
Background and/or Patient History
  • Suspected opioid overdose with respiratory depression
  • Naloxone given intramuscularly
  • Discussion of how naloxone works pharmacologically
Allergies
NKDA
Medications
  • Opioid (suspected overdose)
Current Findings
  • Opioid-induced respiratory depression
  • Naloxone as a reversal agent
  1. Question 1
    Moderate
    Naloxone reverses opioid effects by acting as a:
  2. Question 2
    Hard
    Because naloxone is a competitive antagonist, very high doses of an opioid could in principle:
  3. Question 3
    Moderate
    After the initial reversal, the patient still needs monitoring because:
  4. Question 4
    Moderate
    A non-competitive antagonist, in contrast, would:
  5. Question 5
    Easy
    This case illustrates the distinction between:

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Patient case: Why warfarin needs INR monitoring
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Patient
Female, 68 years old
Chief Complaint
Discussion of why her warfarin dose is monitored so often.
Background and/or Patient History
  • Long-term warfarin for atrial fibrillation
  • Regular INR checks; occasional dose adjustments
  • Asks why monitoring is needed when other medications are not checked
Allergies
NKDA
Medications
  • Warfarin
Current Findings
  • Stable warfarin patient on routine monitoring
  • Discussion of narrow therapeutic index
  1. Question 1
    Moderate
    Warfarin is classified as a:
  2. Question 2
    Moderate
    The therapeutic index (TI) is:
  3. Question 3
    Moderate
    Other drugs with narrow therapeutic indices include:
  4. Question 4
    Moderate
    The clinical implication of a narrow therapeutic index is that:
  5. Question 5
    Moderate
    This explains why, before any dental surgery on this patient, the clinician would:

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Patient case: Hepatotoxicity from too much acetaminophen
0 of 5 answered, 0 correct
Patient
Male, 38 years old
Chief Complaint
Reports taking large quantities of acetaminophen for dental pain over several days.
Background and/or Patient History
  • Took well above the recommended daily dose of acetaminophen for dental pain
  • Now reports nausea and right upper quadrant discomfort
  • Concern for acetaminophen hepatotoxicity
Allergies
NKDA
Medications
  • Acetaminophen (high doses)
Current Findings
  • Possible acetaminophen-induced hepatotoxicity
  • Need for urgent medical evaluation
  1. Question 1
    Hard
    Acetaminophen overdose is dangerous mainly because of:
  2. Question 2
    Moderate
    The antidote for acetaminophen toxicity is:
  3. Question 3
    Hard
    Therapeutic doses of acetaminophen are generally safe because:
  4. Question 4
    Hard
    Chronic alcohol use raises the risk of acetaminophen hepatotoxicity because it:
  5. Question 5
    Easy
    The lesson is that even a 'safe' over-the-counter drug:

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Patient case: Writing a safe dental prescription
0 of 5 answered, 0 correct
Patient
Male, 45 years old
Chief Complaint
Needs a prescription for postoperative analgesia after a routine extraction.
Background and/or Patient History
  • Healthy patient needing an analgesic prescription
  • Clinician completing a written prescription for the pharmacy
  • Standard postoperative pain plan
Allergies
NKDA
Medications
  • None
Current Findings
  • Healthy patient receiving an analgesic prescription
  • Discussion of prescription elements
  1. Question 1
    Moderate
    A complete written prescription should include:
  2. Question 2
    Moderate
    For routine postoperative dental pain in a healthy adult, an effective combination is often:
  3. Question 3
    Moderate
    Adjustments to the dose are commonly needed in:
  4. Question 4
    Easy
    Common 'sig' abbreviations on a prescription include:
  5. Question 5
    Moderate
    Before writing the prescription, the clinician should always:

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