PTCB Pharmacology #1 3 — Questions and Answers
Question 1: Which enzyme does warfarin inhibit to produce its anticoagulant effect?
- Thrombin directly
- Vitamin K epoxide reductase (Correct answer)
- Factor Xa directly
- Plasminogen activator
Correct answer: Vitamin K epoxide reductase
Warfarin inhibits vitamin K epoxide reductase, preventing the recycling of vitamin K. This depletes vitamin K-dependent clotting factors (II, VII, IX, X) and proteins C and S.
Question 2: Statins reduce LDL cholesterol primarily by:
- Binding bile acids in the gut
- Inhibiting HMG-CoA reductase in the liver (Correct answer)
- Blocking intestinal cholesterol absorption
- Activating lipoprotein lipase
Correct answer: Inhibiting HMG-CoA reductase in the liver
Statins competitively inhibit HMG-CoA reductase, the rate-limiting enzyme in cholesterol biosynthesis, reducing intracellular cholesterol and upregulating LDL receptors on hepatocytes.
Question 3: A drug with a narrow therapeutic index (NTI) is best described as:
- A drug that is only effective at very high doses
- A drug where there is little difference between the effective and toxic dose (Correct answer)
- A drug with minimal side effects
- A drug that is available in only one dosage form
Correct answer: A drug where there is little difference between the effective and toxic dose
Narrow therapeutic index drugs (e.g., warfarin, digoxin, lithium, phenytoin) have a small window between therapeutic and toxic concentrations, requiring close monitoring and dose adjustments.
Question 4: Omeprazole (Prilosec) is an example of which type of drug?
- H2 receptor antagonist
- Antacid
- Proton pump inhibitor (Correct answer)
- Sucralfate
Correct answer: Proton pump inhibitor
Omeprazole is a PPI (proton pump inhibitor) that irreversibly inhibits the H+/K+ ATPase. H2 blockers (ranitidine, famotidine) reversibly block histamine H2 receptors on parietal cells.
Question 5: Which of the following neurotransmitters is primarily affected by SSRI antidepressants?
- Dopamine
- GABA
- Norepinephrine
- Serotonin (Correct answer)
Correct answer: Serotonin
SSRIs (selective serotonin reuptake inhibitors) block the serotonin transporter (SERT), increasing synaptic serotonin levels. SNRIs affect both serotonin and norepinephrine.
Question 6: What is a prodrug?
- A drug that bypasses hepatic metabolism entirely
- A drug administered in an inactive form that is converted to the active form in the body (Correct answer)
- A drug with no therapeutic effect until combined with another drug
- The first drug discovered in a pharmacological class
Correct answer: A drug administered in an inactive form that is converted to the active form in the body
A prodrug is pharmacologically inactive until metabolized (usually hepatically) into its active form. Examples include clopidogrel (active metabolite via CYP2C19), enalapril (→enalaprilat), and codeine (→ morphine).
PTCB Pharmacology #1 3
Which enzyme does warfarin inhibit to produce its anticoagulant effect?