A 73-year-old man presents to his primary care physician complaining of a weak stream and nocturia four times at night. He is very sensitive to the medication side effects and is reluctant to take medications for this reason. Physical examination reveals a mildly enlarged prostate. Treatment of this condition may involve the use of which of the following agents to minimize side effects?

Correct Answer: D

Rationale: Tamsulosin is an α1-adrenergic receptor antagonist that is selective for the prostate and bladder neck, minimizing systemic side effects like hypotension.

Correct Answer: B

Rationale: Colchicine is not used for dysmenorrhea; NSAIDs are preferred.

Correct Answer: B

Rationale: Ester-type local anesthetics are hydrolyzed by pseudo cholinesterase in the blood unlike amides which are metabolized in the liver.

Correct Answer: D

Rationale: N-acetylcysteine restores glutathione levels, preventing hepatotoxicity from toxic paracetamol metabolites.

Correct Answer: B

Rationale: Benzodiazepines (e.g., diazepam, lorazepam) are CNS depressants used for anxiety, seizures, and insomnia. They exert effects by binding to a specific allosteric site on the GABAa receptor, enhancing GABA's inhibitory action. GABA, the primary inhibitory neurotransmitter, opens chloride (Cl⁻) channels, hyperpolarizing neurons and reducing excitability. Benzodiazepines increase the frequency of channel opening, potentiating this effect, leading to sedation and anxiolysis. Blocking Cl⁻ channels (choice A) would oppose inhibition, contrary to their purpose. Acting as direct agonists (choice C) is incorrect—they don't activate the receptor alone but amplify GABA's action. Antagonizing GABAb receptors (choice D) is irrelevant, as benzodiazepines target GABAa specifically. This potentiation mechanism underlies their therapeutic utility and risks like tolerance. Understanding this is key to distinguishing benzodiazepines from other CNS drugs and managing their clinical use effectively.