USMLE Step 1 exam Study Guide
This guide is designed to test high-yield pharmacological concepts for the USMLE Step
1 exam. The questions follow the integrated model of the exam, linking pharmacology
to pathophysiology, microbiology, and biochemistry. Each answer is explained to
reinforce the underlying mechanism, adverse effects, and clinical application—the key to
answering Step 1 questions correctly.
Autonomic Nervous System (ANS) Pharmacology
1. A 60-year-old man with hypertension is prescribed a new medication. He
presents with drowsiness, impotence, and bradycardia. Which of the following
drugs is most likely responsible?
ANSWER ✓ Clonidine. It is a central alpha-2 agonist that decreases sympathetic
outflow, leading to these side effects. Sedation and sexual dysfunction are common.
2. A patient with open-angle glaucoma is prescribed eye drops to decrease
aqueous humor production. Which drug class acts via beta-adrenergic receptor
blockade?
ANSWER ✓ Timolol. As a non-selective beta-blocker, it reduces cAMP production in
ciliary epithelium, decreasing aqueous humor production.
3. A farmer is brought to the emergency department after being exposed to an
insecticide. He is salivating, lacrimating, and has bronchospasm and bradycardia.
Which drug is a competitive antagonist at muscarinic receptors used to treat this
condition?
ANSWER ✓ Atropine. It blocks the effects of excess acetylcholine at muscarinic
receptors in organophosphate poisoning.
4. Which drug, used for asthma, is a beta-2 selective agonist and is often
administered via inhalation for its direct bronchodilator effects?
ANSWER ✓ Albuterol (Salbutamol). It selectively activates beta-2 receptors in the
lungs, causing relaxation of bronchial smooth muscle.
5. A patient undergoing surgery is given a reversible cholinesterase inhibitor to
reverse the effects of a non-depolarizing neuromuscular blocker. Which drug is
, used for this purpose?
ANSWER ✓ Neostigmine. It inhibits acetylcholinesterase, increasing ACh at the NMJ to
competitively overcome the blockade.
Cardiovascular & Renal Pharmacology
6. A patient with hypertension is started on a drug that causes dry cough and
angioedema. Which drug class works by inhibiting the conversion of angiotensin I
to angiotensin II?
ANSWER ✓ ACE Inhibitors (e.g., Lisinopril, Enalapril). They increase bradykinin levels,
which is responsible for the dry cough and angioedema.
7. A patient with heart failure is prescribed a drug that blocks angiotensin II
receptors. Which drug class is this?
ANSWER ✓ ARBs (Angiotensin Receptor Blockers) (e.g., Losartan, Valsartan). They
directly block the AT1 receptor, avoiding the bradykinin-related side effects of ACEi.
8. Which class of antiarrhythmic drugs is characterized by sodium channel
blockade and is used for ventricular arrhythmias?
ANSWER ✓ Class Ia (e.g., Quinidine, Procainamide) and Class Ib (e.g., Lidocaine). Ia
prolongs AP duration, while Ib shortens it. Lidocaine is a first-line for VT/VF.
9. A patient with atrial fibrillation is started on a drug that predominantly blocks
the potassium channels, prolonging the action potential duration. Which class is
this?
ANSWER ✓ Class III Antiarrhythmics (e.g., Amiodarone, Sotalol). They prolong
repolarization and the effective refractory period.
10. Which drug, used for hypertension and angina, works by selectively blocking
L-type calcium channels in vascular smooth muscle, leading to vasodilation?
ANSWER ✓ Dihydropyridines (e.g., Nifedipine, Amlodipine). They have greater
selectivity for vascular smooth muscle over cardiac muscle.
11. A patient with CHF is prescribed a drug that inhibits the Na+/K+/2Cl-
cotransporter in the thick ascending limb of the loop of Henle. What is this drug?
ANSWER ✓ Furosemide. It is a loop diuretic that causes potent diuresis and is important
for managing fluid overload in CHF.
12. Which potassium-sparing diuretic acts as a direct antagonist of the aldosterone
receptor?
This guide is designed to test high-yield pharmacological concepts for the USMLE Step
1 exam. The questions follow the integrated model of the exam, linking pharmacology
to pathophysiology, microbiology, and biochemistry. Each answer is explained to
reinforce the underlying mechanism, adverse effects, and clinical application—the key to
answering Step 1 questions correctly.
Autonomic Nervous System (ANS) Pharmacology
1. A 60-year-old man with hypertension is prescribed a new medication. He
presents with drowsiness, impotence, and bradycardia. Which of the following
drugs is most likely responsible?
ANSWER ✓ Clonidine. It is a central alpha-2 agonist that decreases sympathetic
outflow, leading to these side effects. Sedation and sexual dysfunction are common.
2. A patient with open-angle glaucoma is prescribed eye drops to decrease
aqueous humor production. Which drug class acts via beta-adrenergic receptor
blockade?
ANSWER ✓ Timolol. As a non-selective beta-blocker, it reduces cAMP production in
ciliary epithelium, decreasing aqueous humor production.
3. A farmer is brought to the emergency department after being exposed to an
insecticide. He is salivating, lacrimating, and has bronchospasm and bradycardia.
Which drug is a competitive antagonist at muscarinic receptors used to treat this
condition?
ANSWER ✓ Atropine. It blocks the effects of excess acetylcholine at muscarinic
receptors in organophosphate poisoning.
4. Which drug, used for asthma, is a beta-2 selective agonist and is often
administered via inhalation for its direct bronchodilator effects?
ANSWER ✓ Albuterol (Salbutamol). It selectively activates beta-2 receptors in the
lungs, causing relaxation of bronchial smooth muscle.
5. A patient undergoing surgery is given a reversible cholinesterase inhibitor to
reverse the effects of a non-depolarizing neuromuscular blocker. Which drug is
, used for this purpose?
ANSWER ✓ Neostigmine. It inhibits acetylcholinesterase, increasing ACh at the NMJ to
competitively overcome the blockade.
Cardiovascular & Renal Pharmacology
6. A patient with hypertension is started on a drug that causes dry cough and
angioedema. Which drug class works by inhibiting the conversion of angiotensin I
to angiotensin II?
ANSWER ✓ ACE Inhibitors (e.g., Lisinopril, Enalapril). They increase bradykinin levels,
which is responsible for the dry cough and angioedema.
7. A patient with heart failure is prescribed a drug that blocks angiotensin II
receptors. Which drug class is this?
ANSWER ✓ ARBs (Angiotensin Receptor Blockers) (e.g., Losartan, Valsartan). They
directly block the AT1 receptor, avoiding the bradykinin-related side effects of ACEi.
8. Which class of antiarrhythmic drugs is characterized by sodium channel
blockade and is used for ventricular arrhythmias?
ANSWER ✓ Class Ia (e.g., Quinidine, Procainamide) and Class Ib (e.g., Lidocaine). Ia
prolongs AP duration, while Ib shortens it. Lidocaine is a first-line for VT/VF.
9. A patient with atrial fibrillation is started on a drug that predominantly blocks
the potassium channels, prolonging the action potential duration. Which class is
this?
ANSWER ✓ Class III Antiarrhythmics (e.g., Amiodarone, Sotalol). They prolong
repolarization and the effective refractory period.
10. Which drug, used for hypertension and angina, works by selectively blocking
L-type calcium channels in vascular smooth muscle, leading to vasodilation?
ANSWER ✓ Dihydropyridines (e.g., Nifedipine, Amlodipine). They have greater
selectivity for vascular smooth muscle over cardiac muscle.
11. A patient with CHF is prescribed a drug that inhibits the Na+/K+/2Cl-
cotransporter in the thick ascending limb of the loop of Henle. What is this drug?
ANSWER ✓ Furosemide. It is a loop diuretic that causes potent diuresis and is important
for managing fluid overload in CHF.
12. Which potassium-sparing diuretic acts as a direct antagonist of the aldosterone
receptor?
