Which one of the following bactericidal antimycobacterial drugs binds to S12 ribosomal subunit inhibiting protein synthesis when injectable drug is needed and also effective against drug-resistant tuberculosis drug, can cause ototoxicity and nephrotoxicity?

Correct Answer: A

Rationale: The correct answer is A: Streptomycin. Streptomycin binds to the S12 ribosomal subunit, inhibiting protein synthesis in mycobacteria. It is effective against drug-resistant tuberculosis and is used as an injectable drug. Streptomycin is known to cause ototoxicity and nephrotoxicity as side effects. Choice B: Ethambutol inhibits cell wall synthesis in mycobacteria, not protein synthesis. Choice C: Isoniazid inhibits mycolic acid synthesis in the cell wall of mycobacteria. Choice D: Rifampicin inhibits RNA synthesis by binding to the beta subunit of bacterial RNA polymerase.

Correct Answer: C

Rationale: Rationale: C: The diuretic furosemide causes potassium loss (hypokalemia), which can lead to increased toxicity of digoxin. Low potassium levels can enhance the effects of digoxin, resulting in digoxin toxicity. Summary: A: Hypocalcemia is not directly related to digoxin toxicity. B: Hyponatremia is not directly related to digoxin toxicity. D: This choice is incorrect as hypokalemia is a known risk factor for digoxin toxicity.

Correct Answer: C

Rationale: Hydrochlorothiazide (HCTZ) is the correct answer for treating mild hypertension due to its effectiveness in reducing blood volume and lowering blood pressure. HCTZ works by promoting urine production, leading to decreased fluid retention and lower blood pressure. Furosemide (A) is a loop diuretic mainly used for edema and severe hypertension. Spironolactone (B) is a potassium-sparing diuretic often used for heart failure and hyperaldosteronism. Amiloride (D) is another potassium-sparing diuretic used in combination with other diuretics. Overall, HCTZ is preferred for mild hypertension due to its efficacy, safety, and low cost.

Correct Answer: B

Rationale: The correct answer is B: Furosemide. Furosemide is a loop diuretic, which is the most potent type of diuretic that acts on the loop of Henle in the kidney, leading to significant water and electrolyte loss. This excessive diuresis can result in hypovolemia and subsequent hypotension. Acetazolamide (A) is a carbonic anhydrase inhibitor diuretic that works in the proximal tubule and is not as potent as loop diuretics. Spironolactone (C) is a potassium-sparing diuretic that acts on the distal tubule and collecting duct, so it is not as potent as loop diuretics and does not typically cause hypotension from excessive diuresis. Hydrochlorothiazide (D) is a thiazide diuretic that works in the distal convoluted tubule and is less potent than loop diuretics like f

Correct Answer: A

Rationale: The correct answer is A: Amiloride. Spironolactone is a potassium-sparing diuretic that works by inhibiting aldosterone. Combining it with another potassium-sparing diuretic like Amiloride can increase the risk of hyperkalemia. On the other hand, combining Spironolactone with loop diuretics like Furosemide or thiazide diuretics like Chlorthalidone or Hydrochlorothiazide can provide synergistic effects by targeting different parts of the nephron to enhance diuresis without significantly increasing the risk of hyperkalemia. So, combining Spironolactone with Amiloride is not recommended to avoid hyperkalemia.