Antihypertensive Drugs

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Chapter: Medicinal Chemistry : Antihypertensive Drugs

Antihypertensive drugs are defined as the drugs that are used to decrease the elevated blood pressure (hypertension).

Antihypertensive Drugs


Antihypertensive drugs are defined as the drugs that are used to decrease the elevated blood pressure (hypertension).


It is one of the common cardiovascular disorders and it is a state of the body in which the systolic blood pressure (BP) is 150 mm Hg or more and diastolic BP is 95 mm Hg or more. Hypertension may be classified into primary and secondary:


It is other wise known as essential hypertension. It is characterized by the following:

  • Elevation of diastolic BP.

  • Normal cardiac output.

  • An increase in peripheral resistance.


Factors causing secondary hypertension are as follows:

  • Acute or chronic renal disease.

  • Hyperaldosteronism.

  • Cushing’s syndrome.

  • Acromegaly.

  • Pheochromocytoma.

  • Oral contraceptives, steroids, estrogen, and sympathomimetics.

Antihypertensive drug therapy has improved remarkably in the last 50 years. Before 1950, less effective and less tolerated antihypertensive drugs were available. Veratrum and sodium thiocyanate could lower BP, but were toxic and difficult to use. The ganglion blockers that were developed in the 1950s were effective, but inconvenient. Reserpine was a breakthrough, but produced mental depression. The therapeutic potential of hydralazine was not tapped fully because of the marked side effects when it was used alone. Guanithidine introduced in 1961 was an improvement on the ganglion blockers. The antihypertensives of 1960–70s were methyldopa, β-blockers, thiazides, high-ceiling diuretics, and clonidine. The antihypertensives of 1980– 90s are angiotensin II converting enzyme inhibitors and calcium channel blockers. Angiotensin receptor blockers (losartan) are the latest antihypertensives. Diuretics and related drugs are the choice in uncomplicated hypertension. These drugs reduce plasma and extra cellular fluid volume by 5%–15% that decrease cardiac output. The reduction in total peripheral resistance is most probably an indirect consequence of small persisting Na+ and volume defect. Decreased intracellular Na+ concentration in the vascular smooth muscle may decrease stiffness of vessels wall, increase compliance, and dampen responsiveness to constrictor stimuli of noradrenaline and angiotensin II.

Angiotensin-converting enzyme (ACE) inhibitors are one of the first choice drugs in all the grades of essential as well as renovascular hypertension. When it is used alone, 50% of the patients are benefited and the addition of a diuretic/β blocker extends the efficacy to 90%. Angiotensin receptor blockers give peak action at 2–4 weeks. Calcium channel blockers such as dihydropyridines, phenylalkylamine, and benzothiazepine are equally effective antihypertensives. Beta adrenergic blockers give 30%–40% efficacy in mild-tomoderate cases.

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