Tick mebendazole mechanism of action:

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: 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.

Correct Answer: B

Rationale: In treating a patient with congestive heart failure (CHF), selecting the appropriate dosage of dopamine is crucial for its positive inotropic effects. The correct dosage in this scenario is option B) 5-10 mg/kg/min. This dosage range is selected because dopamine acts on specific receptors in the heart that increase contractility, thereby improving cardiac output in CHF. Option A) 2.0 mg/kg/min is too low to produce the desired positive inotropic effects in CHF patients. Option C) 10-20 mg/kg/min is a higher dosage range that may lead to excessive vasoconstriction and increased afterload, potentially worsening the patient's condition. Option D) 40 mg/kg/min is an extremely high dosage that can cause severe vasoconstriction, leading to decreased coronary perfusion and worsening of CHF symptoms. Educationally, understanding the rationale behind selecting the appropriate dosage of dopamine in CHF patients is essential for healthcare professionals involved in managing cardiovascular diseases. It emphasizes the importance of dosing precision to achieve therapeutic effects while minimizing adverse outcomes. By grasping the pharmacological principles behind dopamine's effects on the cardiovascular system, clinicians can make informed decisions tailored to each patient's specific condition, ultimately improving patient outcomes.

Correct Answer: B

Rationale: In this scenario, the correct answer is B) Is coadministered with fluconazole. Terfenadine is a non-sedating antihistamine that was withdrawn from the market due to its potential to cause fatal arrhythmias by prolonging the QT interval. Fluconazole is an antifungal medication that inhibits the metabolism of terfenadine, leading to increased levels of terfenadine in the body. This increased concentration can further prolong the QT interval, predisposing the individual to polymorphic ventricular tachycardia like Torsades de Pointes. Option A) Is coadministered with azithromycin is incorrect because azithromycin does not have a significant interaction with terfenadine. Option C) Is given in higher doses is incorrect because the risk of polymorphic ventricular tachycardia is related to drug interactions and not just higher doses of terfenadine alone. Option D) Reduces QT interval is incorrect because terfenadine actually prolongs the QT interval, which is why it can lead to serious cardiac arrhythmias. This question highlights the importance of understanding drug interactions, particularly those that can impact cardiac electrophysiology. Healthcare providers need to be aware of potential drug interactions that can lead to QT prolongation and associated arrhythmias to ensure patient safety when prescribing medications that affect the cardiovascular system.