ACEI and Hypertension

Angiotensin converting enzyme inhibitors (ACEIs) interfere with the enzymatic conversion of angiotensin I (A-I) into angiotensin II (A-II), a substance that increases blood pressure. ACEIs inhibit the converting enzyme so the body makes less A-II. Numerous ACEIs have been approved by the Food and Drug Administration since 1981 for the treatment of hypertension and other cardiovascular diseases. The generic names of these drugs all end in "-pril," such as captopril, enalapril and lisonopril.

The Role of Angiotensin II in Hypertension

• Renin made by the kidneys interacts with circulating angiontensinogen to make A-I. Angiotensin converting enzyme (ACE) reacts with A-I to make A-II. A-II tightens the blood vessels, which increases blood pressure. A-II also influences the production of aldosterone, which causes sodium and water retention and increases blood pressure. Cardiovascular Pharmacology notes that ACE also breaks down bradykinin, a natural substance that relaxes the blood vessels. The body uses ACE to regulate blood pressure, but persistent effects contribute to chronic hypertension, changes in the heart and vascular system and, in time, heart failure.

ACEI Benefits

• Because ACEIs reduce A-II levels, they help expand blood vessels and reduce aldosterone production. ACEIs have particular value in the treatment of unilateral renal artery stenosis, which also causes high blood pressure. The drugs' effectiveness and tolerability have made them among the most prescribed hypertension medications.

Adverse Effects

• Although similar in many respects, each ACEI may have some side effect and warning different from the others. Patients generally tolerate ACEIs well. Dry cough occurs in some patients. Hyperkalemia (increased potassium levels) can occur, though combination therapy with a diuretic usually prevents it. Angioedema (dangerous swelling of the airways) can also occur, though uncommonly.

Professional Guidelines

• The Seventh Report of the Joint National Committee for hypertension (JNC-7), issued by the National Heart Lung and Blood Institute in 2004, recommends first-line treatment with a thiazide diuretic, preferred for a good safety profile and low cost. ACEIs have their place in JNC-7 guidelines, along with beta blockers, calcium channel blockers and other hypertensive drugs. The American Society of Hypertension lists ACEIs in combination with diuretics or calcium channel blockers as one of the preferred combination treatments for high blood pressure.

Clinical Data

• An analysis of 92 clinical trials from 1966 through 2007 by Balraj Heran found "no meaningful differences" among the various ACEIs in their blood-pressure-reducing effects. Dose ranging trials included in the analysis found blood-pressure reductions improved with dosage. However, the rate of improvement tapered off and stopped as the doses approached the maximum recommended dose.