Which of the following drugs is used to treat anaphylaxis?

Correct Answer: A

Rationale: The correct answer is A: Epinephrine. Epinephrine is the drug of choice for treating anaphylaxis due to its rapid action in constricting blood vessels, relaxing smooth muscles, and opening airways. It helps counteract the severe allergic reaction and can save a person's life. Diphenhydramine (B) is an antihistamine that can help relieve itching and hives but is not as effective or fast-acting as epinephrine in treating anaphylaxis. Loratadine (C) is also an antihistamine, which is used for allergies but not for immediate treatment of anaphylaxis. Ibuprofen (D) is a nonsteroidal anti-inflammatory drug (NSAID) used for pain relief and inflammation, but it does not have the life-saving properties needed to treat anaphylaxis.

Correct Answer: B

Rationale: The correct answer is B: Sedation. Opioid analgesics commonly cause sedation due to their central nervous system depressant effects. They act on opioid receptors in the brain, leading to drowsiness and sedation. Diarrhea (A) is more commonly associated with opioid-induced constipation. Hypertension (C) is not a common adverse effect of opioids; they are more likely to cause hypotension. Hypokalemia (D) is not directly linked to opioid use. Sedation is the most prevalent adverse effect of opioids, making it the correct choice here.

Correct Answer: B

Rationale: The correct answer is B because ACE inhibitors work by inhibiting the conversion of angiotensin I to angiotensin II. Angiotensin II is a potent vasoconstrictor and also stimulates the release of aldosterone, leading to increased blood pressure. By blocking this conversion, ACE inhibitors help dilate blood vessels and reduce blood pressure. A: Blocking calcium channels is the mechanism of action of calcium channel blockers, not ACE inhibitors. C: Inhibiting aldosterone is the mechanism of action of aldosterone receptor antagonists, not ACE inhibitors. D: Increasing bradykinin levels is a side effect of ACE inhibitors, but not their primary mechanism of action.

Correct Answer: A

Rationale: The correct answer is A: Inhibiting sodium reabsorption in the kidneys. Hydrochlorothiazide is a thiazide diuretic that works by inhibiting the sodium-chloride symporter in the distal convoluted tubule of the kidneys, leading to increased excretion of sodium and water. This results in decreased blood volume and subsequently lowers blood pressure. Explanation of incorrect choices: B: Increasing sodium retention in the kidneys - This is the opposite effect of what hydrochlorothiazide does. C: Blocking calcium channels in the blood vessels - This is the mechanism of action for calcium channel blockers, not thiazide diuretics. D: Inhibiting ACE in the lungs - This is the mechanism of action for ACE inhibitors, not thiazide diuretics.

Correct Answer: B

Rationale: The correct answer is B: Non-competitive antagonist. This is because a non-competitive antagonist binds irreversibly to a different site on the receptor compared to the agonist (norepinephrine in this case) and prevents its activation, leading to a decrease in response. In the graph, the presence of Drug X shifts the concentration-response curve of norepinephrine downward without affecting the maximum response, indicating non-competitive antagonism. A: Silent antagonists do not affect the agonist's binding or activity on the receptor. C: Competitive antagonists compete with the agonist for the same binding site on the receptor, affecting potency but not the maximum response. D: Chemical antagonist is a broad term for any antagonist that binds to the agonist or receptor to prevent activation but does not specifically describe the mechanism like non-competitive antagonism does.