Telmisartan lowers blood pressure by:
**Core Concept**
Telmisartan is an angiotensin II receptor antagonist (ARB) that plays a key role in the renin-angiotensin-aldosterone system (RAAS). By blocking the effects of angiotensin II, telmisartan leads to vasodilation and a subsequent decrease in blood pressure.
**Why the Correct Answer is Right**
Telmisartan selectively binds to the angiotensin type 1 (AT1) receptor, preventing the vasoconstrictive and aldosterone-secreting effects of angiotensin II. This blockade results in decreased peripheral resistance and a subsequent decrease in blood pressure. The RAAS pathway is activated in response to decreased blood volume or pressure, where renin cleaves angiotensinogen to form angiotensin I, which is then converted to angiotensin II by angiotensin-converting enzyme (ACE).
**Why Each Wrong Option is Incorrect**
**Option A:** This option is likely a distractor related to another class of antihypertensive agents, such as beta-blockers or calcium channel blockers.
* Beta-blockers work by reducing heart rate and contractility, while calcium channel blockers cause vasodilation by blocking L-type calcium channels in vascular smooth muscle cells.
**Option B:** This option might be related to the mechanism of ACE inhibitors, which also target the RAAS pathway but at a different step.
* ACE inhibitors block the conversion of angiotensin I to angiotensin II, leading to decreased angiotensin II levels and vasodilation.
**Option C:** This option could be related to diuretics, which work by increasing sodium and water excretion.
* Diuretics decrease blood volume, leading to decreased blood pressure, but their mechanism is distinct from that of ARBs like telmisartan.
**Clinical Pearl / High-Yield Fact**
Telmisartan has a favorable metabolic profile, including neutral effects on glucose and lipid metabolism, making it a suitable option for patients with diabetes or dyslipidemia. This is in contrast to some other antihypertensive agents, which may worsen these conditions.
**Correct Answer: C. Blockade of angiotensin II at the AT1 receptor.**