MBBS Pharmacology 1 — Questions and Answers
Question 1: Which antibiotic class inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs)?
- Aminoglycosides
- Fluoroquinolones
- Beta-lactams (Correct answer)
- Macrolides
Correct answer: Beta-lactams
Beta-lactam antibiotics (penicillins, cephalosporins, carbapenems) inhibit cell wall synthesis by irreversibly binding to PBPs, preventing peptidoglycan cross-linking.
Question 2: Which drug is a competitive antagonist at the beta-1 adrenergic receptor used in heart failure?
- Metoprolol (Correct answer)
- Phenylephrine
- Dobutamine
- Milrinone
Correct answer: Metoprolol
Metoprolol is a cardioselective beta-1 blocker that reduces heart rate and myocardial oxygen demand, improving outcomes in heart failure with reduced ejection fraction.
Question 3: The mechanism of action of statins involves inhibition of which enzyme?
- Lipoprotein lipase
- HMG-CoA reductase (Correct answer)
- Cholesterol ester transfer protein
- Pancreatic lipase
Correct answer: HMG-CoA reductase
Statins inhibit HMG-CoA reductase, the rate-limiting enzyme in cholesterol synthesis, leading to upregulation of LDL receptors and decreased plasma LDL.
Question 4: Which opioid analgesic has the highest oral bioavailability and is often used in opioid maintenance therapy?
- Morphine
- Codeine
- Methadone (Correct answer)
- Fentanyl
Correct answer: Methadone
Methadone has high oral bioavailability (~80%), a long half-life, and is used in opioid use disorder maintenance therapy.
Question 5: Which antiepileptic drug acts by prolonging the inactivation state of voltage-gated sodium channels?
- Ethosuximide
- Phenytoin (Correct answer)
- Valproate
- Clonazepam
Correct answer: Phenytoin
Phenytoin stabilizes the inactive state of voltage-gated Na+ channels, preventing rapid repetitive neuronal firing without affecting normal neural function.
Question 6: ACE inhibitors reduce angiotensin II levels and are contraindicated in pregnancy primarily because they cause:
- Neural tube defects
- Fetal renal dysgenesis and oligohydramnios (Correct answer)
- Cardiac septal defects
- Cleft palate
Correct answer: Fetal renal dysgenesis and oligohydramnios
ACE inhibitors in the 2nd and 3rd trimester cause fetal renal tubular dysplasia, leading to oligohydramnios, limb contractures, and neonatal renal failure.
MBBS Pharmacology 1
Which antibiotic class inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs)?