Cardiovascular drugs are used to treat diseases affecting the heart and blood vessels, such as heart attacks, angina, hypertension, arrhythmias, blood clots, and hyperlipidemias, such as high cholesterol. They can be categorized below, with some drugs belonging to multiple categories.
Antihypertensives are drugs that lower blood pressure. Currently marketed ones include diuretics, beta-blockers, calcium channel blockers, ACE (angiotensin-converting enzyme) inhibitors, Angiotensin II receptor blockers (ARBs), centrally acting antihypertensives, alpha blockers, aldosterone antagonists, renin inhibitors and vasodilators. Many drugs are sold as a combination of two or sometimes three medications.
Diuretics: Commonly known as water pills, diuretics reduce blood pressure by increasing the excretion of water and salt through the kidney. Diuretics have different classes depending on their mechanism of action. Thiazide diuretics are commonly used antihypertensives. Examples of thiazides (brand names in brackets) include hydrochlorothiazide (Microzide, Oretic, HydroDiuril), chlorothiazide (Diuril), chlorthalidone (Thalitone), indapamide (Coversyl) and metolazone (Mykrox). Loop diuretics act on the loop of Henle in the kidney. Examples of loop diuretics are furosemide (Lasix), torsemide (Soaanz, Demadex), bumetanide (Bumex), and ethacrynic acid (Edecrin). Potassium sparing diuretics are another class of diuretics and include spironolactone (Aldactone, Carospir), triamterene (Dyrenium), amiloride (Midamor,) and eplerenone (Inspra).
Diuretics may cause side effects like increased frequency of urination and electrolyte imbalances especially hypokalemia and calcium imbalances. They may precipitate gout by increasing the serum levels of uric acid. Potassium sparing diuretics may cause hyperkalemia or high blood potassium levels, which may cause cardiac arrest in severe cases. Hence it is important to monitor serum electrolyte levels after starting diuretic therapy. Loop diuretics and thiazides contain a sulfa group and should be avoided in patients with sulfa allergies.
Beta blockers: Beta blockers block beta receptors on the heart and blood vessels, which causes relaxation of blood vessels and decrease in cardiac output by slowing the heart rate and contraction, leading to a decrease in blood pressure. Beta blockers have a generic name stem -olol. Commonly used beta blockers include metoprolol (Lopressor, Toprol XL), nebivolol (Bystolic), propranolol (Inderal), acebutolol (Sectral), atenolol (Tenormin) and carvedilol (Coreg). Adverse effects include dizziness, bradycardia, fatigue, and constipation. They may precipitate asthma attacks in asthmatic patients. They may mask symptoms of low blood sugar and hence should be taken with caution in diabetics. Suddenly stopping beta blockers may cause a dangerous increase in blood pressure.
Calcium channel blockers: Calcium channel blockers block calcium channels that are located in the heart and/or blood vessels. This slows down the contraction of the heart and dilates the blood vessels, leading to a drop in blood pressure. Some of them are commonly used as antihypertensives. Examples include amlodipine ( Katerzia, Norliqva, Norvasc), nifedipine (Procardia, Adalat CC), diltiazem (Cardizem, Tiazac), and verapamil (Verelan, Calan). Adverse effects include dizziness, headache, edema, bradycardia, constipation, and reflex tachycardia.
ACE (angiotensin-converting enzyme) inhibitors: ACE inhibitors block the enzyme angiotensin converting enzyme (ACE) that catalyzes the conversion of angiotensin I to angiotensin II. These chemicals increase blood pressure. ACE inhibitors reduce the levels of angiotensin II and hence help to decrease blood pressure and dilate the arteries and veins. ACE inhibitors have the generic name stem -pril. Common examples include lisinopril (Carace, Zestril, Zestoretic, Prinivil), ramipril (Lopace, Triapin, Tritace, Altace), benazepril (Lotensin), captopril (Acepril, Capozide, Capoten, Acezide), enalapril (Innovace, Innozide, Vasotec, Epaned), trandolapril (Mavik, Tarka, Gopten) and perindopril (Coversyl, Aceon). Adverse effects include dry cough, hyperkalemia, headache and angioedema. Dry cough after taking ACE inhibitors is a result of raised levels of a chemical mediator called bradykinin.
Angiotensin II receptor blockers (ARBs): ARBs block angiotensin II receptors, known as AT I receptors, on blood vessels and heart. They block the action of angiotensin II, thus decreasing blood pressure. Unlike ACE inhibitors, ARBs do not precipitate cough. ARBs have the generic name stem -sartan. Common ARBs include losartan (Cozaar), valsartan (Diovan), telmisartan (Micardis), irbesartan (Avapro), candesartan (Atacand), olmesartan (Benicar) and azilsartan (Edarbi). Adverse effects include hyperkalemia, dizziness, and angioedema.
Centrally acting antihypertensives: They are a special group of antihypertensives that block a part of the autonomic nervous system known as sympathetic nervous system in the medulla. The medulla is located in the brain, and it has many specialized areas including the control center for the sympathetic nervous system. Centrally acting antihypertensives reduce blood pressure by activating the alpha 2 receptor in the medulla which inhibits the sympathetic outflow to the cardiovascular system. Examples include clonidine (Catapres, Kapvay), methyldopa (Aldomet), and guanfacine (Intuniv). Adverse effects include edema, sedation, dry mouth, depression, bradycardia, orthostatic hypotension, impotence, constipation, gastric upset, and rebound hypertension on sudden discontinuation. Methyldopa is used as an antihypertensive in pregnant patients.
Alpha blockers: They dilate arteries and veins by blocking alpha 1 receptors on blood vessels. Examples include prazosin (Minipress), terazosin (Hytrin) and doxazosin (Cardura). Adverse effects include dizziness, orthostatic hypotension, nasal congestion, headache, reflex tachycardia and fluid retention. Alpha blockers are also used in the treatment of benign prostatic hyperplasia.
Aldosterone antagonists: They are a subtype of potassium sparing diuretics that can also block the aldosterone receptor. Aldosterone is a hormone that increases blood pressure. Aldosterone antagonists are used in the treatment of hypertension, heart failure, certain disorders of the kidney, and hormonal imbalances. Examples include spironolactone (Aldactone, Carospir), eplerenone (Inspra), and finerenone (Kerendia). Adverse effects include dizziness, hyperkalemia, muscle cramps, cough, upset stomach, breast tenderness, gynecomastia, and erectile dysfunction. Compared to older aldosterone antagonists like spironolactone, newer drugs like eplerenone and finerenone have a lower risk of erectile dysfunction and gynecomastia.
Renin inhibitors: Inhibits the renal enzyme renin which catalyzes the conversion of angiotensinogen to angiotensin I. As a result, angiotensin I levels reduce leading to dilation of arteries and veins. Adverse effects include diarrhea, cough, angioedema and hyperkalemia. Renin inhibitors are contraindicated in pregnancy. Aliskiren (Tekturna) is available in the United States.
Vasodilators: Vasodilators are medications that dilate blood vessels by relaxing smooth muscle in the vessel wall. Some of them are useful as antihypertensives. They may also be used to treat angina and heart failure. They may preferentially dilate arteries or veins. Examples include hydralazine (Apresoline), minoxidil (Loniten), and nitrates such as nitroglycerine (Nitrostat) and nitroprusside (Nipride RTU, Nitropress). Drugs classified under other groups also have vasodilating properties. They include calcium channel blockers, ARBs, ACE inhibitors, and some beta blockers like nebivolol and carvedilol.
Hydralazine, minoxidil, sodium nitroprusside, and nitroglycerine are also known as direct vasodilators as they dilate arteries and arterioles and significantly reduce the vascular resistance. Nitrates preferentially dilate veins by releasing nitric oxide, which dilates blood vessels. Minoxidil opens potassium channels on the smooth muscle cells of blood vessel,s causing dilation. Adverse effects of vasodilators include reflex tachycardia, headache and edema. Cyanide toxicity may occur with nitroprusside as a result of metabolic breakdown of the drug. Tolerance may develop due to the long-term use of nitrates. Nitrates are contraindicated with sildenafil (Viagra) and other drugs in the same class, like tadalafil (Cialis) and vardenafil (Levitra). The use of hydralazine for more than three months has been associated with lupus-like syndrome with joint pain, arthritis, rash, and systemic effects. Minoxidil promotes hair growth and is used in the treatment of baldness.
Combination antihypertensives: Many antihypertensives are used in combination of two or three drugs in the same pill. Combination pills may help with patient adherence to antihypertensive therapy, reduce adverse effects, and may decrease the cost of treatment. Common formulas use a combination of a diuretic with ACE inhibitor/Angiotensin receptor blocker/beta blocker/another diuretic/, or Renin inhibitor with calcium channel blocker, or calcium channel blocker plus ACE inhibitor/Angiotensin receptor blocker.
Commonly used examples include the following:
Amlodipine plus benazepril (Lotrel)
Amlodipine plus perindopril (Prestalia)
Amlodipine plus olmesartan (Azor)
Benazepril plus hydrochlorothiazide (Lotensin HCT)
Enalapril plus hydrochlorothiazide (Vaseretic)
Candesartan plus hydrochlorothiazide (Atacand HCT)
Losartan plus hydrochlorothiazide (Hyzaar)
Olmesartan plus hydrochlorothiazide (Benicar HCT)
Metoprolol plus hydrochlorothiazide (Lopressor HCT)
Valsartan plus hydrochlorothiazide (Diovan HCT)
Telmisartan plus hydrochlorothiazide (Micardis HCT)
Hydrochlorothiazide and triamterene (Dyazide; Maxzide)