PEBC Pharmacology Basics 4 — Questions and Answers
Question 1: Tachyphylaxis refers to:
- Allergic reaction developing on repeated drug exposure
- Rapid decrease in drug response following repeated administration (Correct answer)
- Increased sensitivity to a drug over time
- Cross-reactivity between structurally similar drugs
Correct answer: Rapid decrease in drug response following repeated administration
Tachyphylaxis is a rapid, short-term decrease in response to a drug after repeated doses, often due to receptor desensitization or depletion of mediators.
Question 2: A drug with high plasma protein binding would be expected to have:
- Higher free drug concentration available for effect
- Reduced volume of distribution (Correct answer)
- Faster renal clearance
- Greater susceptibility to first-pass metabolism
Correct answer: Reduced volume of distribution
Highly protein-bound drugs have less free drug in plasma to distribute into tissues, resulting in a lower apparent volume of distribution.
Question 3: Which of the following best describes a prodrug?
- A drug that is immediately active after administration
- An inactive compound converted to an active metabolite in the body (Correct answer)
- A drug requiring dose adjustment in renal impairment
- A compound that inhibits metabolic enzymes
Correct answer: An inactive compound converted to an active metabolite in the body
A prodrug is pharmacologically inactive and must be metabolized (typically by the liver) to an active form to exert its therapeutic effect.
Question 4: The Henderson-Hasselbalch equation is used in pharmacology primarily to:
- Calculate drug half-life
- Predict the degree of drug ionization at a given pH (Correct answer)
- Determine renal clearance
- Estimate protein binding affinity
Correct answer: Predict the degree of drug ionization at a given pH
The Henderson-Hasselbalch equation relates pH, pKa, and ionization, allowing prediction of the proportion of ionized vs. non-ionized drug at a given pH.
Question 5: Enteric coating on a tablet is designed primarily to:
- Enhance drug absorption in the stomach
- Prevent dissolution until the tablet reaches the small intestine (Correct answer)
- Increase drug bioavailability by 50%
- Slow absorption for extended release
Correct answer: Prevent dissolution until the tablet reaches the small intestine
Enteric coating resists gastric acid and dissolves only at the higher pH of the intestine, protecting acid-labile drugs or the gastric mucosa from irritating compounds.
Question 6: Which type of drug interaction occurs when two drugs compete for the same plasma protein binding sites?
- Pharmacodynamic synergism
- Pharmacokinetic displacement interaction (Correct answer)
- Receptor antagonism
- Enzyme induction
Correct answer: Pharmacokinetic displacement interaction
Displacement interactions occur when one drug displaces another from protein binding sites, transiently increasing the free (active) concentration of the displaced drug.
Question 7: A drug that activates a receptor and produces the OPPOSITE effect of the endogenous ligand is called:
- Partial agonist
- Competitive antagonist
- Inverse agonist (Correct answer)
- Allosteric modulator
Correct answer: Inverse agonist
An inverse agonist binds to the same receptor as the agonist but stabilizes an inactive conformation, reducing constitutive activity and producing effects opposite to the agonist.
