A 60-year-old female with chronic pain is prescribed gabapentin. Gabapentin works by:

Correct Answer: C

Rationale: The correct answer is C because gabapentin binds to calcium channels in the central nervous system. This action reduces the release of excitatory neurotransmitters, such as glutamate, which helps in reducing pain signals sent to the brain. Option A is incorrect as gabapentin does not directly affect serotonin levels. Option B is incorrect as gabapentin does not inhibit norepinephrine reuptake. Option D is incorrect as gabapentin does not increase dopamine release. Therefore, the correct mechanism of action for gabapentin is binding to calcium channels to modulate pain signaling.

Correct Answer: A

Rationale: The correct answer is A: Fluoxetine. Fluoxetine is a selective serotonin reuptake inhibitor (SSRI) commonly used to treat depression by increasing serotonin levels in the brain. This drug specifically targets the reuptake of serotonin, leading to higher levels available in the brain to improve mood. Choice B: Amitriptyline is a tricyclic antidepressant, not an SSRI, and works by affecting the balance of certain neurotransmitters in the brain. Choice C: Sertraline is another SSRI used for depression, but it is not the correct answer in this case. Choice D: Mirtazapine is a different class of antidepressant called a noradrenergic and specific serotonergic antidepressant (NaSSA), not an SSRI. Therefore, the correct choice is A, Fluoxetine, as it is the only SSRI listed among the options provided.

Correct Answer: B

Rationale: The correct answer is B: Metformin. Metformin is the first-line treatment for type 2 diabetes mellitus due to its effectiveness, safety profile, and low cost. It works by decreasing glucose production in the liver and improving insulin sensitivity. Insulin (choice A) is usually reserved for when other treatments fail. Sulfonylureas (choice C) can cause weight gain and hypoglycemia. DPP-4 inhibitors (choice D) are typically used as second-line agents.

Correct Answer: A

Rationale: The correct answer is A: Blocking aldosterone receptors. Spironolactone is a potassium-sparing diuretic that works by blocking aldosterone receptors in the distal convoluted tubules of the kidneys. By inhibiting aldosterone, spironolactone reduces sodium and water retention, decreases potassium excretion, and helps reduce fluid overload in heart failure patients. Choices B, C, and D are incorrect because spironolactone does not directly increase sodium and water excretion in the kidneys, inhibit the action of angiotensin II, or block beta-1 adrenergic receptors in the heart.

Correct Answer: B

Rationale: The correct answer is B: Phosphodiesterase type 5 inhibitors (PDE5 inhibitors) are used for treating erectile dysfunction by increasing blood flow to the penis. Beta-blockers (A), ACE inhibitors (C), and diuretics (D) are not indicated for erectile dysfunction treatment as they do not target the underlying physiological mechanisms responsible for erectile function. PDE5 inhibitors specifically target the vasodilation process in the penis, leading to improved erectile function.