The applications of the ganglion blockers have disappeared because of all of the following reasons EXCEPT:

Correct Answer: D

Rationale: The correct answer is D: Respiratory depression. Ganglion blockers were used to treat conditions like hypertension by blocking sympathetic and parasympathetic ganglia. Respiratory depression is not a reason for the disappearance of ganglion blockers. A. Orthostatic hypotension is a common side effect due to extensive blockade of sympathetic ganglia. B. Lack of selectivity leads to non-specific effects on various organ systems. C. Homeostatic reflexes block disrupts normal physiological responses leading to adverse effects. Overall, respiratory depression is not a prominent reason for the decline in the use of ganglion blockers compared to the other listed reasons.

Correct Answer: C

Rationale: 1. Nonselective alpha-receptor antagonists like phenoxybenzamine are used in treating Pheochromocytoma. 2. Pheochromocytoma is a tumor that causes excess release of catecholamines leading to severe hypertension. 3. Alpha-blockers help control blood pressure by blocking the vasoconstrictive effects of catecholamines. 4. Choice A is incorrect as alpha-blockers can worsen asthma due to bronchoconstriction. 5. Choice B is incorrect as alpha-blockers may worsen arrhythmias by reducing cardiac contractility. 6. Choice D is incorrect as alpha-blockers are not typically first-line for chronic hypertension.

Correct Answer: D

Rationale: The correct answer is D because alterations in hepatic function due to disease can affect drug metabolism, old age can alter drug clearance rates, and drug-induced changes in microsomal enzyme activities can impact drug metabolism. Each factor directly influences the biodisposition of hypnotic agents by affecting their metabolism and elimination. Therefore, all of the factors mentioned in choices A, B, and C can influence the biodisposition of hypnotic agents.

Correct Answer: B

Rationale: The correct answer is B: Primidone. Primidone is a prodrug that is metabolized in the liver to phenobarbital, which is the active antiseizure component. This process allows for a more controlled and sustained release of phenobarbital in the body. Phenytoin (A) works by blocking sodium channels, Felbamate (C) works by multiple mechanisms, and Vigabatrin (D) works by increasing GABA levels. These mechanisms are different from Primidone's pathway of being converted into phenobarbital.

Correct Answer: C

Rationale: Rationale: MAO-A primarily metabolizes norepinephrine and serotonin, as these neurotransmitters are broken down in the synaptic cleft. MAO-B mainly metabolizes dopamine. Thus, choice C is correct. Choices A, B, and D are incorrect because they inaccurately assign the neurotransmitters to MAO-A and MAO-B, leading to an incorrect understanding of their functions.