A 65-year-old female with chronic pain is prescribed celecoxib. Celecoxib works primarily by:

Correct Answer: B

Rationale: The correct answer is B because celecoxib selectively inhibits COX-2 enzymes, which are responsible for producing prostaglandins involved in pain and inflammation. By targeting COX-2 specifically, celecoxib reduces pain and inflammation without affecting COX-1, which is important for maintaining gastrointestinal mucosa and platelet function. Therefore, choice A is incorrect as celecoxib does not inhibit both COX-1 and COX-2. Choices C and D are also incorrect as celecoxib does not increase prostaglandin synthesis or bind to opioid receptors.

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: B

Rationale: Correct Answer: B - Inhibiting the production of clotting factors by the liver Rationale: 1. Warfarin is a vitamin K antagonist that inhibits the production of vitamin K-dependent clotting factors (Factors II, VII, IX, X) by the liver. 2. By reducing the production of these clotting factors, warfarin helps prevent blood clots in patients with conditions like atrial fibrillation. 3. Thrombin is a key enzyme in the blood clotting process, but warfarin does not directly inhibit its action. 4. Blocking platelet aggregation is the mechanism of action for antiplatelet drugs like aspirin, not warfarin. 5. Inhibiting fibrinogen activation is not a mechanism of action for warfarin, as it primarily targets the production of clotting factors.

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.