Which of the following statements about spironolactone is TRUE?

Correct Answer: D

Rationale: In this question, option D is the correct answer: "All of the above." A) Spironolactone reverses many of the manifestations of aldosteronism. This statement is true because spironolactone is a mineralocorticoid receptor antagonist, which inhibits the action of aldosterone. This leads to the reversal of aldosterone-mediated effects such as sodium retention and potassium excretion. B) Spironolactone is also an androgen antagonist and is used in the treatment of hirsutism in women. This statement is true as spironolactone has anti-androgenic properties, making it effective in treating conditions like hirsutism by blocking the effects of androgens on hair follicles. C) Spironolactone is useful as a diuretic. This statement is true as spironolactone is a potassium-sparing diuretic that works by promoting the excretion of sodium and water while retaining potassium. Educationally, understanding the mechanisms of action of spironolactone is crucial for pharmacology students and healthcare professionals to effectively use this medication in clinical practice. Knowing that spironolactone can reverse aldosteronism manifestations, act as an androgen antagonist, and serve as a diuretic helps in selecting the appropriate indications for its use and monitoring for potential side effects.

Correct Answer: B

Rationale: Rationale: Trimethoprim inhibits dihydropteroate reductase, an enzyme in the folate synthesis pathway in bacteria, disrupting DNA and protein synthesis. This leads to bacterial cell death. Cyclooxygenase (Choice A) is targeted by NSAIDs, not trimethoprim. Dihydropteroate synthase (Choice C) is targeted by sulfonamides, not trimethoprim. DNA gyrase (Choice D) is targeted by fluoroquinolones, not trimethoprim. Therefore, Choice B is correct for trimethoprim's mechanism of action.

Correct Answer: A

Rationale: The correct answer is A because niclosamide works by increasing cell membrane permeability for calcium in helminthes. This leads to paralysis, dislodgement, and ultimately death of the parasites. Choice B is incorrect because niclosamide does not work by blocking acetylcholine transmission at the myoneural junction. Choice C is incorrect as niclosamide does not inhibit microtubule synthesis or impair glucose uptake in helminthes. Choice D is incorrect as niclosamide does not inhibit oxidative phosphorylation in helminthes.

Correct Answer: B

Rationale: Step-by-step rationale: 1. Estrogens are contraindicated in most cancers due to their potential to promote cancer growth. 2. However, in prostate cancer, estrogens can be used as a form of androgen deprivation therapy. 3. Estrogen therapy in prostate cancer helps suppress testosterone production, slowing cancer growth. 4. Hence, the correct indication for estrogens in oncological practice is prostate cancer. Summary: A, C, and D are incorrect because estrogen therapy is not indicated in leukemia, endometrial cancer, or brain tumors due to the risk of promoting cancer growth. Prostate cancer is the exception where estrogens can be beneficial for treatment.

Correct Answer: B

Rationale: The correct answer is B: Atrial fibrillation. Atrial fibrillation is characterized by irregular and rapid heart rhythm originating in the atria. This is the most likely disorder based on the given information, as it matches the symptoms described. Premature ventricular contractions (A) are extra, abnormal heartbeats originating in the ventricles. Second-degree atrioventricular block (C) is a conduction disorder between the atria and ventricles. Polymorphic ventricular tachycardia (D) is a serious arrhythmia characterized by irregular heartbeats. However, based on the patient's symptoms, atrial fibrillation is the most likely diagnosis.