What are the first-line antihypertensive agents and their principal mechanisms?

• A. Beta blockers only
• B. Thiazide diuretics (NaCl reabsorption inhibition), ACE inhibitors/ARBs (RAAS blockade), and calcium channel blockers (DHP or non-DHP) depending on comorbidity
• C. Direct renin inhibitors only
• D. Alpha blockers only

Answer: (D)

The main idea is which drug classes are considered appropriate to start treatment for hypertension and how they work. The first-line options are thiazide diuretics, ACE inhibitors or ARBs, and calcium channel blockers, with the choice guided by the patient’s other health problems. Thiazide diuretics work by inhibiting sodium chloride reabsorption in the distal tubule of the nephron, causing a mild diuresis that lowers plasma volume and, over time, reduces peripheral vascular resistance to lower blood pressure. ACE inhibitors and ARBs block the renin–angiotensin–aldosterone system—ACE inhibitors prevent the formation of angiotensin II, while ARBs block its receptor—leading to vasodilation and reduced aldosterone-mediated volume expansion; this class is particularly protective for patients with diabetes or kidney disease and can be preferred when a patient has these comorbidities. Calcium channel blockers prevent calcium entry into vascular smooth muscle and, depending on the subtype, cause vasodilation (DHPs) or affect the heart’s conduction and rate more directly (non-DHPs); DHPs are often used for uncomplicated hypertension and isolated systolic hypertension, while non-DHPs are chosen when there are coexisting rate or rhythm concerns but require caution in patients with conduction issues.

Other agents like beta-blockers or alpha blockers are not typically first-line for essential hypertension unless there is a specific comorbidity (such as coronary disease, heart failure, arrhythmias, or benign prostatic hyperplasia) that makes them particularly suitable, and direct renin inhibitors are not generally first-line due to limited outcome data in this setting.