Antihypertensive Drugs

Antihypertensive drugs

DEFINITION
Antihypertensive drugs are medicines that help lower blood pressure.
Purpose

All antihypertensive agents lower blood pressure, although the mechanisms of action vary greatly. Within this therapeutic class, there are several subgroups. There are a very large number of drugs used to control hypertension, and the drugs listed below are representatives, but not the only members of their classes.

Description
The calcium channel blocking agents, also called slow channel blockers or calcium antagonists, inhibit the movement of ionic calcium across the cell membrane. This reduces the force of contraction of heart muscles and arteries. Although the calcium channel blockers are treated as a group, there are four different chemical classes, leading to significant variations in the activity of individual drugs.

Nifedipine (Adalat, Procardia) has the greatest effect on the blood vessels,

Verapamil (Calan, Isoptin) and Diltiazem (Cardizem) have a greater effect on the heart muscle itself.

Peripheral vasodilators such as

Hydralazine (Apresoline),

Isoxuprine (Vasodilan), and

Minoxidil (Loniten) act by relaxing blood vessels.

There are several groups of drugs that act by reducing adrenergic nerve stimulation, the excitatory nerve stimulation that causes contraction of the muscles in the arteries, veins, and heart.

These drugs include the

1) beta-adrenergic blockers and

2) alpha/beta adrenergic blockers. There are also

3) non-specific adrenergic blocking agents.

Beta-adrenergic blocking agents include

propranolol (Inderal),

atenolol (Tenormin), and

pindolol (Visken).

Propranolol acts on the beta-adrenergic receptors anywhere in the body, and has been used as a treatment for emotional anxiety and rapid heart beat.

Atenolol and Acebutolol (Sectral) act specifically on the nerves of the heart and circulation.

There are two alpha/beta adrenergic blockers,

Lbetolol (Normodyne, Trandate) and

Cavedilol (Coreg). These work similarly to the beta blockers.

(ACE inhibitors)
Angiotensin-converting enzyme inhibitors act by inhibiting the production of angiotensin II, (a substance that induces both constriction of blood vessels and retention of sodium, which leads to water retention and increased blood volume).

There are 10 ACE inhibitors currently marketed in the United States, including

captopril (Capoten),

benazepril (Lotensin),

enalapril (Vasotec), and

quinapril (Acupril).

The primary difference between these drugs is their onset and duration of action.
The ACE II inhibitors,

losartan (Cozaar),

candesartan (Atacand),

irbesartan (Avapro),

telmisartan (Micardis),

valsartan (Diovan), and

eprosartan (Teveten)

directly inhibit the effects of ACE II rather than blocking its production.

Their actions are similar to the ACE inhibitors, but they appear to have a more favorable side effect and safety profile.

In addition to these drugs, other classes of drugs have been used to lower blood pressure,

most notably the

Thiazide diuretics.

There are 12 thiazide diuretics marketed in the United States, including hydrochlorothiazide (Hydrodiuril, Esidrex),

indapamide (Lozol),

polythiazide (Renese), and

hydroflumethiazide (Diucardin).

The drugs in this class appear to lower blood pressure through several
Antihypertensive Drugs

Brand Name (Generic Name)
Possible Common Side Effects Include:
Accupril (quinapril hydrochloride)
Headache, dizziness

Aldatazide
Diarrhea, fever, headache, decreased coordination

Aldactone (spironolactone)
Cramps, drowsiness, stomach disorders

Aldomet (methyldopa)
Fluid retention, headache, weak feeling

Altace (ramipril)
Headache, cough

Calan, Calan SR (verapamil hydrochloride)
Constipation, fatigue, decreased blood pressure

Capoten (captopril)
Decreased sense of taste, decreased blood pressure tiching, rash

Cardene (nicardipine Hydrochloride)
Dizziness, headache, indigestion and nausea, increased heartbeat

Cardizem (diltiazem hydrochloride)
Dizziness, fluid retention, headache, nausea, skin rash

Cardura (doxazosin mesylate)
Dizziness, fatigue, drowsiness, headache

Catapres
Dry mouth, drowsiness, dizziness, constipation

Corgard (nadolol)
Behaviorial changes, dizziness, decreased heartbeat, tiredness

Corzide
Dizziness, decreased heartbeat, fatigue, cold hands and feet

Diuril (chlorothiazide)
Cramps, constipation or diarrhea, dizziness, fever, increased glocose level in urine

Dyazide
Blurred vision, muscle and abdominal pain, fatigue

DynaCirc (isradipine)
Chest pain, fluid retention, headache, fatigue

HydroDIURIL (hydrochlorothiazide)
Upset stomach, headache, cramps, loss of appetite
Hygroton (chlorthalidone)
Anemia, constipation or diarrhea, cramps, itching
Hytrin (terazosin hydrochloride)
Dizziness, labored breathing, nausea, swelling
Inderal (propranolol hydrochloride)
Constipation or diarrhea, tingling sensation, nausea and vomiting
Inderide
Blurred vision, cramps, fatigue, loss of appetite
Lasix (furosemide)
Back and muscle pain, indigestion, nausea
Lopressor (metoprolol tartrate)
Diarrhea, itching/rash, tiredness
Lotensin (benazepril hydrochloride)
Nausea, dizziness, fatigue, headache
Alozol (indapamide)
Anxiety, headache, loss of energy, muscle cramps
Maxzide
Cramps, labored breathing, drowsiness, irritated stomach
Minipress (prazosin hdrochloride)
Headache, nausea, weakness, dizziness
Moduretic
Diarrhea, fatigue, itching, loss of appetite
Monopril (fosinopril sodium)
Nausea and vomiting, headache, cough
Normodyne (labetalol hydrochloride)
Fatigue, nausea, stuffy nose
Plendil (felodipine)
Pain in back, chest, muscles, joints, and abdomen, itching, dry mouth, respiratory problems
Procardia, Procardia X (nifedipine)
Swelling, constipation, decreased blood pressure, nausea, fatigue
Sectral (acebutolol hydrochloride)
Constipation or diarrhea, gas, chest and joint pain
Ser-Ap-Es
Blurred vision, cramps, muscle pain, dizziness
Tenex (guanfacine hydrochloride)
Headache, constipation, dry mouth, weakness
Tenoretic
Decreased heartbeat, fatigue, nausea
Tenormin (atenolol)
Nausea, fatigue, dizziness
Veseretic
Diarrhea, muscle cramps, rash
Vasotec (enalapril maleate)
Chest pain, blurred vision, constipation or diarrhea, hives, nausea
Visken (pindolol)
Muscle cramps, labored breathing, nausea, fluid retention
Wytensin (guanabenz acetate)
Headache, drowsiness, dizziness
Zaroxolyn (metolazone)
Constipation or diarrhea, chest pain, spasms, nausea
Zestoretic (lisinopril hydrochlorothiazide)
Fatigue, headache, dizziness
Zestril (lisinopril)
Labored breathing, abdominal and chest pain, nausea, decreased blood pressure
mechanisms. By promoting sodium loss they lower blood volume. At the same time, the pressure of the walls of blood vessels, the peripheral vascular resistance, is lowered. Thiazide diuretics are commonly used as the first choice for reduction of mild hypertension, and may be used in combination with other antihypertensive drugs.
Sodium nitroprusside (Nitropress) and

diazoxide (Hyperstat)

are used for rapid treatment of hypertensive emergencies. They are given by vein, often during surgery, to reduce blood pressure that suddenly becomes elevated.
Many classes of antihypertensive drugs have been used before surgery to maintain a low blood pressure during the procedure. There does not appear to be a significant difference between drugs when they are used for blood pressure reduction during surgery.

Recommended dosage
Recommended dosage

varies with patient,

drug, severity of hypertension,

and whether

the drug is being used alone or

in combination with other drugs.

Patients should consult specialized references or ask a physician for further information.

Precautions
The warnings and precautions given below apply to the use of antihypertensive drugs over a long period of time. These adverse effects are generally not a problem when the drugs are given as a single dose prior to surgery.
Because of the large number of classes and individual drugs in this group, patients should ask their physicians about specific drugs.
Peripheral vasodilators may cause dizziness and orthostatic hypotension—a rapid lowering of blood pressure when the patient stands up in the morning. Patients taking these drugs must be instructed to rise from bed slowly. Pregnancy risk factors for this group are generally category C, meaning they may result in adverse affects on the fetus. Hydralazine has been shown to cause cleft palate in animal studies, but there is no human data available. Breastfeeding is not recommended.
ACE inhibitors are generally well tolerated, but may rarely cause dangerous reactions including laryngospasm and angioedema. Persistent cough is a common side effect. ACE inhibitors should not be used in pregnancy. When used in pregnancy during the second and third trimesters, ACE inhibitors can cause injury to and even death in the developing fetus. When pregnancy is detected, discontinue the ACE inhibitor as soon as possible. Breastfeeding is not recommended.
ACE II inhibitors are generally well tolerated and do not cause cough. Pregnancy risk factor is category C during the first trimester and category D (known to cause adverse effects in the fetus) during the second and third trimesters. Drugs that act directly on the renin-angiotensin system can cause fetal and neonatal morbidity and death when administered to pregnant women. Several dozen cases have been reported in patients who were taking ACE inhibitors. When pregnancy is detected, discontinue ACE inhibitors as soon as possible. Breast-feeding is not recommended.
Thiazide diuretics commonly cause potassium depletion. Patients should have potassium supplementation either through diet, or potassium supplements. Pregnancy risk factor is category B (chlorothiazide, chlorthalidone, hydrochlorothiazide, indapamide, metolazone) or category C (bendroflumethiazide, benzthiazide, hydroflumethiazide, methyclothiazide, trichlormethiazide). Routine use during normal pregnancy is inappropriate. Thiazides are found in breast milk. Breastfeeding is not recommended.
Beta blockers may cause a large number of adverse reactions including dangerous heart rate abnormalities. Pregnancy risk factor is category B (acebutolol, pindolol, sotalol) or category C (atenolol, labetalol, esmolol, metoprolol, nadolol, timolol, propranolol, penbutolol, carteolol, bisoprolol). Breastfeeding is not recommended.
Interactions
Patients should ask their doctors and consult specific references for food and drug interactions.