Which of the following synthetic steroids shows predominantly mineralocorticoid action?

Correct Answer: D

Rationale: The correct answer is D: Fludrocortisone. Fludrocortisone is a synthetic steroid that primarily exhibits mineralocorticoid activity. It is commonly used to treat adrenal insufficiency due to its potent mineralocorticoid effects. Hydrocortisone (A) is a natural steroid with both glucocorticoid and mineralocorticoid activity. Spironolactone (B) is a potassium-sparing diuretic that acts as an aldosterone antagonist, reducing the effects of aldosterone. Dexamethasone (C) is a synthetic steroid with potent anti-inflammatory and immunosuppressive properties but minimal mineralocorticoid activity.

Correct Answer: B

Rationale: Step-by-step rationale for choice B (Taking of drinks with alkaline pH) being correct: 1. Sulfonamides are more soluble in alkaline solutions, reducing the risk of precipitation. 2. Alkaline pH helps in preventing the formation of crystals in the urine. 3. Alkaline drinks can help maintain a higher urinary pH, minimizing the risk of crystalluria. 4. This approach is supported by medical literature and pharmacological principles. Summary: - Choice A (Taking of drinks with acid pH) is incorrect as it may exacerbate sulfonamide precipitation and crystalluria. - Choice C (Taking of saline drinks) is incorrect as it does not address the solubility issues of sulfonamides. - Choice D (Restriction of drinking) is incorrect as hydration is essential to prevent crystalluria.

Correct Answer: B

Rationale: The correct answer is B: Metronidazole. Metronidazole is the drug of choice for extraluminal amebiasis due to its high efficacy against Entamoeba histolytica. It is a nitroimidazole antibiotic that works by disrupting the DNA structure of the parasite. Other choices are incorrect because: A: Iodoquinol is mainly used for luminal amebiasis. C: Diloxanide is also used for luminal amebiasis. D: Tetracycline is not the first-line treatment for extraluminal amebiasis.

Correct Answer: A

Rationale: The correct answer is A: Inhibition of dihydrofolate reductase. Methotrexate inhibits dihydrofolate reductase, an enzyme involved in the synthesis of nucleotides. This leads to decreased production of DNA, RNA, and proteins, inhibiting cell proliferation. Choices B and C are incorrect as methotrexate does not activate cell differentiation or deplete serum asparagine. D is incorrect as methotrexate's mechanism of action is specifically through inhibiting dihydrofolate reductase, not all of the above.

Correct Answer: B

Rationale: The correct answer is B: Sotalol. Sotalol is a non-selective beta-blocker and a class III antiarrhythmic agent that blocks both beta receptors and potassium (K+) channels. By blocking beta receptors, it decreases heart rate and contractility. Blocking K+ channels prolongs the action potential duration, aiding in the treatment of various arrhythmias. Quinidine (A) is a class I antiarrhythmic that primarily blocks Na+ channels. Propranolol (C) is a selective beta-blocker that does not affect K+ channels. Digoxin (D) is a cardiac glycoside that inhibits the sodium-potassium pump but does not block beta receptors or K+ channels.