Which of the following is a potassium-sparing diuretic?

Correct Answer: B

Rationale: Spironolactone is a potassium-sparing diuretic that works by blocking the effects of aldosterone in the distal tubules of the kidney, leading to increased excretion of sodium and water while retaining potassium. This class of diuretics helps to conserve potassium, making them suitable for patients at risk of hypokalemia. In contrast, furosemide, hydrochlorothiazide, and bumetanide are loop diuretics, thiazide diuretics, and another loop diuretic, respectively, which all promote the loss of potassium along with sodium and water.

Correct Answer: B

Rationale: Protamine is the antidote for Heparin. Heparin is an anticoagulant medication that prevents the formation of blood clots. In case of an overdose of Heparin or if there is a need to reverse its effects quickly (such as during surgery), Protamine is administered as the specific antidote. Protamine works by binding to Heparin and neutralizing its anticoagulant effects. Therefore, Protamine is the appropriate antidote to counteract the effects of Heparin.

Correct Answer: C

Rationale: An agonist is a substance that binds to a receptor and triggers a biological response. By activating the receptor, an agonist mimics the action of the body's natural ligand that typically binds to the receptor. This activation may lead to a cascade of events within the cell, resulting in a specific physiological response. In contrast, antagonists block the receptor from being activated, while agonists work by binding to the receptor and initiating the desired response.

Correct Answer: C

Rationale: Ondansetron is a medication commonly used to prevent nausea and vomiting, particularly in patients receiving chemotherapy or undergoing surgery. Its mechanism of action involves blocking the effects of serotonin, specifically by antagonizing serotonin 5-HT3 receptors in the chemoreceptor trigger zone of the brain and the gastrointestinal tract. By inhibiting serotonin signaling, ondansetron helps to alleviate nausea and vomiting in affected individuals. This action is distinct from the other options provided, making option C the correct answer for the drug Ondansetron.

Correct Answer: A

Rationale: Stimulants are drugs that increase the body's activity levels. They work on the central nervous system to enhance alertness, attention, and energy. Examples of stimulants include caffeine, amphetamines, and nicotine. Stimulants can increase heart rate, blood pressure, and metabolism, leading to heightened physical and mental activity.