Tick the drug belonging to antibiotics-monobactams:

Correct Answer: C

Rationale: Step-by-step rationale for why choice C (Aztreonam) is correct: 1. Monobactams are a class of antibiotics with a unique monocyclic beta-lactam ring structure. 2. Aztreonam is the only monobactam antibiotic listed among the choices. 3. Aztreonam is effective against aerobic Gram-negative bacteria. 4. It does not have cross-reactivity with beta-lactamases. Summary: A, B, and D are incorrect because they belong to different classes of antibiotics (penicillins, penicillin combinations, and carbapenems respectively), not monobactams.

Correct Answer: C

Rationale: The correct answer is C. Mebendazole inhibits microtubule synthesis in helminths, leading to irreversible impairment of glucose uptake. This disrupts the helminths' ability to maintain their structure and energy production, ultimately causing their death. A, B, and D are incorrect as mebendazole does not work by inhibiting oxidative phosphorylation, increasing cell membrane permeability for calcium, or blocking acetylcholine transmission. These mechanisms are not associated with mebendazole's mode of action.

Correct Answer: D

Rationale: The correct answer is D: Anastrozole. Anastrozole is an aromatase inhibitor that works by blocking the enzyme aromatase, which is responsible for converting androgens into estrogen. By inhibiting estrogen production, Anastrozole effectively reduces estrogen levels in the body. Leuprolide (A) is a gonadotropin-releasing hormone agonist that suppresses estrogen production indirectly. Tamoxifen (B) is a selective estrogen receptor modulator that blocks estrogen receptors. Flutamide (C) is an antiandrogen that blocks the effects of androgens, not estrogen.

Correct Answer: A

Rationale: The correct answer is A: Lovastatin. Lovastatin is a statin medication that can increase the risk of bleeding, which would be problematic for a patient with hemophilia and external hemorrhoids. Statins can interfere with the liver's production of clotting factors, exacerbating bleeding issues in hemophiliac patients. Choice B: Cholestyramine is a bile acid sequestrant used to lower cholesterol levels and is not directly contraindicated in hemophilia or hemorrhoids. Choice C: Ezetimibe is a cholesterol absorption inhibitor and does not directly affect bleeding risk in hemophiliac patients with hemorrhoids. Choice D: Niacin is a B vitamin that can cause flushing and itching, but it does not have a direct contraindication in patients with hemophilia and external hemorrhoids.

Correct Answer: C

Rationale: The correct answer is C because cholestyramine can bind to propranolol in the gut, preventing its absorption and leading to an increase in oral bioavailability. This occurs due to the cholestyramine-propranolol complex being excreted in the feces, reducing the amount of propranolol available for systemic circulation. Choice A is incorrect because propranolol clearance would decrease, not increase, as less drug is absorbed and more is excreted in the feces. Choice B is incorrect as cholestyramine does not directly affect the clearance of hydrochlorothiazide. Choice D is incorrect as there is a clear pharmacokinetic interaction between cholestyramine and propranolol.