Repeated USMLE Questions Step 1 Review- 129- Pharmacology

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Q- Which of the following best describes the mechanism of action of carvedilol in treating high blood pressure?

A- Calcium channel blocker in vascular smooth muscle

B- Central α₂-adrenergic stimulation

C- Nonselective β-adrenergic blockade with α₁-adrenergic blockade

D- Selective β₁-adrenergic blockade only

C- Carvedilol is a nonselective β-blocker (β₁ and β₂) with additional α₁-blocking activity. β-blockade decreases heart rate, myocardial contractility, and renin release. α₁-blockade causes peripheral vasodilation, reducing systemic vascular resistance. This combined effect lowers both cardiac output and total peripheral resistance, making it effective for hypertension and heart failure.

 

Q- Which of the following best describes the mechanism of action of carbamazepine in treating trigeminal neuralgia?

A- Blockade of N-type calcium channels in presynaptic neurons

B- Blockade of voltage-gated sodium channels, reducing neuronal firing

C- Enhancement of GABA-A receptor activity

D- Inhibition of serotonin reuptake in the brain

B- Carbamazepine is an antiepileptic drug that works by blocking voltage-gated channels in neuronal membranes. This action stabilizes the inactivated state of the sodium channel, preventing repetitive and high-frequency firing of action potentials. In trigeminal neuralgia, this dampens ectopic discharges in the trigeminal nerve, relieving the severe facial pain.

 

Q- Which of the following best describes the mechanism of action of propranolol in treating essential tremors?

A- Enhancement of GABAergic neurotransmission in the CNS

B- Nonselective β-adrenergic blockade reduces peripheral β₂-mediated activity

C- Selective β₁-adrenergic blockade decreases heart rate

D- Stimulation of β₂-adrenergic receptors in skeletal muscle

B- Propranolol is a nonselective β-blocker that inhibits both β₁ and β₂ adrenergic receptors. In essential tremor, blocking β₂ receptors in skeletal muscle reduces the sensitivity of muscle spindles and dampens tremor amplitude. This mechanism is peripheral and not primarily CNS-mediated.

 

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