Benzodiazepines produce their actions on CNS by:

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.

Correct Answer: A

Rationale: The patient's oversedation and spending the whole day dozing is a common side effect of Zolpidem, which is a sedative-hypnotic drug used for insomnia. Zolpidem is known to cause drowsiness and oversedation, especially in the elderly population. The patient taking a "sleeping pill" from a friend that he couldn't remember the name of is consistent with Zolpidem being the cause of his symptoms.

Correct Answer: D

Rationale: In the treatment of insomnia, drugs that enhance GABAergic activity are commonly prescribed as they help promote relaxation and sleep. GABA is the major inhibitory neurotransmitter in the brain, and increasing its activity can lead to sedative effects, making it a likely target for a hypnotic drug.

Correct Answer: B

Rationale: Vigabatrin inhibits GABA transaminase

Correct Answer: D

Rationale: The correct answer is D. Increased skeletal muscle tone, fever, skeletal muscle contractions, and diaphoresis are signs of malignant hyperthermia, a rare but life-threatening condition triggered by certain anesthesia agents like halothane and succinylcholine in susceptible individuals. This condition can lead to severe metabolic and respiratory acidosis, cardiac arrhythmias, and hyperkalemia.