BHS Pharmacology and Therapeutics 1 — Questions and Answers
Question 1: What term describes the time required for the plasma concentration of a drug to decrease by 50%?
- Half-life (Correct answer)
- Bioavailability
- Clearance rate
- Volume of distribution
Correct answer: Half-life
Half-life (t½) is the time it takes for the concentration of a drug in the bloodstream to be reduced by half, influencing dosing frequency.
Question 2: Which route of drug administration provides 100% bioavailability?
- Intravenous (IV) (Correct answer)
- Oral
- Subcutaneous
- Transdermal
Correct answer: Intravenous (IV)
Intravenous administration delivers the drug directly into systemic circulation, bypassing first-pass metabolism and achieving 100% bioavailability.
Question 3: What is the 'therapeutic index' of a drug?
- The ratio between the toxic dose and the effective dose (Correct answer)
- The time to peak drug effect
- The percentage of the drug absorbed by the body
- The speed at which a drug is metabolized
Correct answer: The ratio between the toxic dose and the effective dose
The therapeutic index (TI) is the ratio of the toxic dose to the effective dose, indicating how safe a drug is; a narrow TI requires careful monitoring.
Question 4: Which liver enzyme system is primarily responsible for the metabolism of most drugs in humans?
- Cytochrome P450 (CYP450) (Correct answer)
- Monoamine oxidase (MAO)
- Acetylcholinesterase
- Alcohol dehydrogenase
Correct answer: Cytochrome P450 (CYP450)
The cytochrome P450 enzyme family in the liver metabolizes the majority of pharmaceutical drugs, and interactions at these enzymes cause many drug-drug interactions.
Question 5: A patient taking a beta-blocker for hypertension develops bradycardia. This is an example of which type of drug effect?
- Adverse drug reaction (side effect) (Correct answer)
- Allergic reaction
- Drug-drug interaction
- Idiosyncratic reaction
Correct answer: Adverse drug reaction (side effect)
Bradycardia is a predictable side effect of beta-blockers due to their mechanism of slowing heart rate, classifying it as an adverse drug reaction.
Question 6: Which class of antibiotics works by inhibiting bacterial cell wall synthesis?
- Penicillins and cephalosporins (Correct answer)
- Fluoroquinolones
- Macrolides
- Tetracyclines
Correct answer: Penicillins and cephalosporins
Penicillins and cephalosporins (beta-lactam antibiotics) inhibit enzymes required for bacterial cell wall synthesis, causing cell lysis and death.
BHS Pharmacology and Therapeutics 1
What term describes the time required for the plasma concentration of a drug to decrease by 50%?