Which of the following medications is used for the management of hypertension by inhibiting calcium ion entry into smooth muscle cells?

Correct Answer: A

Rationale: Step 1: Amlodipine is a calcium channel blocker that inhibits calcium ion entry into smooth muscle cells. Step 2: By blocking calcium influx, amlodipine relaxes blood vessels, reducing blood pressure. Step 3: Enalapril is an ACE inhibitor, not a calcium channel blocker. Step 4: Clonidine is a centrally acting alpha-2 adrenergic agonist, not a calcium channel blocker. Step 5: Hydrochlorothiazide is a thiazide diuretic, not a calcium channel blocker.

Correct Answer: C

Rationale: The correct answer is C: Inhibiting the If current in the sinoatrial node. Ivabradine is a selective inhibitor of the If current in the sinoatrial node, which results in lowering the heart rate without affecting other parameters like contractility or blood pressure. By reducing the If current, ivabradine slows down the heart rate, making it an effective treatment for heart failure patients. Explanation of other choices: A: Increasing the heart rate - This is incorrect because ivabradine actually decreases the heart rate. B: Blocking beta-adrenergic receptors - This is incorrect as ivabradine works through a different mechanism by inhibiting the If current. D: Increasing myocardial contractility - This is incorrect because ivabradine primarily targets heart rate and does not directly affect myocardial contractility.

Correct Answer: B

Rationale: The correct answer is B because salbutamol is a beta-2 adrenergic receptor agonist, which leads to bronchodilation by relaxing bronchial smooth muscle. This mechanism helps to relieve bronchoconstriction in asthma. Option A is incorrect as leukotriene receptors are not targeted by salbutamol. Option C is incorrect because salbutamol does not inhibit histamine release. Option D is incorrect as salbutamol does not increase mucus production; in fact, it may help reduce mucus secretion by improving airflow.

Correct Answer: A

Rationale: The correct answer is A: Blocking histamine receptors in the brain. Hydroxyzine is a first-generation antihistamine that exerts its effects by blocking histamine receptors, leading to its antihistaminic, sedative, and anxiolytic properties. The other choices (B, C, and D) are incorrect because hydroxyzine does not primarily affect serotonin levels, acetylcholine receptors, or opioid receptors in the brain. Serotonin reuptake inhibitors, anticholinergics, and opioids work through different mechanisms compared to hydroxyzine.

Correct Answer: A

Rationale: The correct answer is A: Methotrexate. Methotrexate is a disease-modifying antirheumatic drug (DMARD) that suppresses the immune system to reduce inflammation in rheumatoid arthritis. It helps to slow down the progression of the disease and prevent joint damage. Prednisone (B) is a corticosteroid that helps reduce inflammation but does not suppress the immune system in the same way as Methotrexate. Aspirin (C) is a nonsteroidal anti-inflammatory drug (NSAID) that helps with pain and inflammation but does not alter the immune response. Hydroxychloroquine (D) is an antimalarial drug that can be used to treat rheumatoid arthritis but does not primarily suppress the immune system like Methotrexate.