Following agent is generally used in allergic rhinitis

Correct Answer: D

Rationale: All of these are corticosteroids commonly used for allergic rhinitis due to their anti-inflammatory effects.

Correct Answer: A

Rationale: Closed head injury (choice A) contraindicates morphine due to respiratory depression and ICP elevation, masking neurological signs. MI (choice B), pulmonary edema (choice C), and diarrhea (choice D) benefit from morphine. This exception ensures safety.

Correct Answer: C

Rationale: Phenytoin follows nonlinear (saturation) kinetics meaning small dose increases can cause disproportionate rises in blood levels.

Correct Answer: B

Rationale: Triamterene is a potassium-sparing diuretic that inhibits Na+ channels in the distal tubule reducing K+ loss.

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.