Therapy of Hypertension (Hypertensive Therapy): Pharmacology Notes

Therapy of Hypertension

Hypertension, often called high blood pressure, is a medical condition characterized by elevated blood pressure levels in the arteries. Blood pressure is a measure of the force of blood against the walls of the arteries as the heart pumps it throughout the body. It is expressed as two values:

The International Society of Hypertension (ISH) classifies hypertension, also known as high blood pressure, based on specific blood pressure ranges. The ISH classification is similar to that of other major organizations, such as the American College of Cardiology (ACC) and the American Heart Association (AHA). Here are the ISH classifications for hypertension:

Normal Blood Pressure:
Systolic Blood Pressure (SBP): Less than 120 mm Hg
Diastolic Blood Pressure (DBP): Less than 80 mm Hg

Elevated Blood Pressure:
Systolic Blood Pressure (SBP): 120-129 mm Hg
Diastolic Blood Pressure (DBP): Less than 80 mm Hg

Hypertension Stage 1:
Systolic Blood Pressure (SBP): 130-139 mm Hg
Diastolic Blood Pressure (DBP): 80-89 mm Hg

Hypertension Stage 2:
Systolic Blood Pressure (SBP): 140 mm Hg or higher
Diastolic Blood Pressure (DBP): 90 mm Hg or higher

The therapy of hypertension, also known as high blood pressure, involves various classes of medications that target different mechanisms to lower blood pressure. Here is a list of common antihypertensive drug classes and their mechanisms of action:

Diuretics:

Mechanism of Action: Diuretics promote the removal of excess sodium and water from the body, reducing blood volume and thereby lowering blood pressure. They primarily work on the kidneys to increase urine production.

Examples: Thiazide diuretics (e.g., hydrochlorothiazide), loop diuretics (e.g., furosemide), potassium-sparing diuretics (e.g., spironolactone).

Beta-Blockers:

Mechanism of Action: Beta-blockers reduce blood pressure by blocking the effects of adrenaline (epinephrine) on the heart and blood vessels, thereby reducing heart rate and cardiac output.

Examples: Atenolol, metoprolol, propranolol.

Angiotensin-Converting Enzyme (ACE) Inhibitors:

Mechanism of Action: ACE inhibitors block the conversion of angiotensin I to angiotensin II, a potent vasoconstrictor. This leads to vasodilation and reduced blood pressure.

Examples: Lisinopril, enalapril, captopril.

Angiotensin II Receptor Blockers (ARBs):

Mechanism of Action: ARBs block the effects of angiotensin II by binding to its receptors, leading to vasodilation and reduced blood pressure.

Examples: Losartan, valsartan, irbesartan.

Calcium Channel Blockers:

Mechanism of Action: Calcium channel blockers inhibit the influx of calcium ions into smooth muscle cells of blood vessels and the heart, leading to vasodilation and reduced heart contractility.

Examples: Amlodipine, verapamil, diltiazem.

Alpha-Blockers:

Mechanism of Action: Alpha-blockers block alpha-adrenergic receptors in blood vessel walls, causing relaxation of the smooth muscles and dilation of blood vessels, which lowers blood pressure.

Examples: Doxazosin, prazosin, terazosin.

Alpha-Beta Blockers:

Mechanism of Action: Alpha-beta blockers block both alpha and beta-adrenergic receptors, leading to a reduction in heart rate and relaxation of blood vessels.

Examples: Labetalol, carvedilol.

Direct Vasodilators:

Mechanism of Action: These medications directly relax the smooth muscles in blood vessel walls, leading to vasodilation and reduced blood pressure.

Examples: Hydralazine, minoxidil.

Renin Inhibitors:

Mechanism of Action: Renin inhibitors reduce the production of angiotensin I, which ultimately lowers the levels of angiotensin II and reduces blood pressure.

Examples: Aliskiren.

Centrally Acting Agents:

Mechanism of Action: These drugs act on the central nervous system to reduce sympathetic nerve impulses, leading to lowered heart rate and vasodilation.

Examples: Clonidine, methyldopa.