Antihypertensive drugs
Definition
Antihypertensive drugs are medicines that help lower blood pressure.
Purpose
The overall class of antihypertensive agents lowers blood pressure, although
the mechanisms of action vary greatly. In 2003, a Joint National Committee on
Prevention, Detection, Evaluation, and Treatment of High Blood Pressure report
said that recent clinical trials show that antihypertensive treatment can reduce
incidence of stroke by 35-40%, heart attack by 20-25%, and onset of new heart
failure by 50%. Within this therapeutic class, there are several subgroups of
drugs. There are a large number of drugs used to control hypertension, and the
drugs listed below are representative, but not the only members of their
classes.
Antihypertensive DrugsBrand
Name (Generic Name)Possible Common
Side Effects Include:Accupril (quinapril
hydrochloride)Headache, dizzinessAldatazideDiarrhea,
fever, headache, decreased coordinationAldactone
(spironolactone)Cramps, drowsiness, stomach
disordersAldomet (methyldopa)Fluid
retention, headache, weak feelingAltace
(ramipril)Headache, coughCalan,
Calan SR (verapamil hydrochloride)Constipation,
fatigue, decreased blood pressureCapoten
(captopril)Decreased sense of taste, decreased
blood pressure tiching, rashCardene (nicardipine
Hydrochloride)Dizziness, headache, indigestion and
nausea, increased heartbeatCardizem (diltiazem
hydrochloride)Dizziness, fluid retention,
headache, nausea, skin rashCardura (doxazosin
mesylate)Dizziness, fatigue, drowsiness, headacheCatapresDry
mouth, drowsiness, dizziness, constipationCorgard
(nadolol)Behaviorial changes, dizziness, decreased
heartbeat, tirednessCorzideDizziness,
decreased heartbeat, fatigue, cold hands and feetDiuril
(chlorothiazide)Cramps, constipation or diarrhea,
dizziness, fever, increased glocose level in urineDyazideBlurred
vision, muscle and abdominal pain, fatigueDynaCirc
(isradipine)Chest pain, fluid retention, headache,
fatigueHydroDIURIL (hydrochlorothiazide)Upset
stomach, headache, cramps, loss of appetiteHygroton
(chlorthalidone)Anemia, constipation or diarrhea,
cramps, itchingHytrin (terazosin
hydrochloride)Dizziness, labored breathing,
nausea, swellingInderal (propranolol
hydrochloride)Constipation or diarrhea, tingling
sensation, nausea and vomitingInderideBlurred
vision, cramps, fatigue, loss of appetiteLasix
(furosemide)Back and muscle pain, indigestion,
nauseaLopressor (metoprolol tartrate)Diarrhea,
itching/rash, tirednessLotensin (benazepril
hydrochloride)Nausea, dizziness, fatigue, headacheAlozol
(indapamide)Anxiety, headache, loss of energy,
muscle crampsMaxzideCramps,
labored breathing, drowsiness, irritated stomachMinipress
(prazosin hdrochloride)Headache, nausea, weakness,
dizzinessModureticDiarrhea,
fatigue, itching, loss of appetiteMonopril
(fosinopril sodium)Nausea and vomiting, headache,
coughNormodyne (labetalol
hydrochloride)Fatigue, nausea, stuffy nosePlendil
(felodipine)Pain in back, chest, muscles, joints,
and abdomen, itching, dry mouth, respiratory problemsProcardia,
Procardia X (nifedipine)Swelling, constipation,
decreased blood pressure, nausea, fatigueSectral
(acebutolol hydrochloride)Constipation or
diarrhea, gas, chest and joint painSer-Ap-EsBlurred
vision, cramps, muscle pain, dizzinessTenex
(guanfacine hydrochloride)Headache, constipation,
dry mouth, weaknessTenoreticDecreased
heartbeat, fatigue, nauseaTenormin (atenolol)Nausea,
fatigue, dizzinessVesereticDiarrhea,
muscle cramps, rash
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 muscles of the heart 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, while 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
beta-adrenergic blockers and alpha/beta adrenergic blockers. There are also
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, labetolol (Normodyne, Trandate)
and carvedilol (Coreg). These work similarly to the beta blockers.
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 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.
Debate continued in 2003 as to the best drugs to lower blood pressure. One
study seemed to prove that diuretics were the best initial choice, but a study
from Australia said that ACE inhibitors were a superior choice. However, many
physicians agreed that the best treatment for a particular patient depends on
his or her particular age, economic situation, genetic factors and other
existing illnesses and conditions.
While designed to lower cholesterol rather than blood pressure, a large
clinical trial reported in 2003 that people with high blood pressure may one day
benefit from taking them. In the trial, participants with increased risk for
heart disease, even if it was not from high cholesterol, benefited from taking
statins.
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.
Specialized references can be consulted for further information.
Precautions
Because of the large number of classes and individual drugs in this group,
specialized references offer more complete information.
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. Hydralazine has
been shown to cause cleft palate in animal studies, but there is no human data
available. Breastfeeding is not recommended.
ACE inhibitors generally are well tolerated, but rarely may 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, angiotension-converting
inhibitors (ACEIs) 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
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, AIIRAs
should be discontinued as soon as possible. Breastfeeding 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. In 2003, a report announced that adavances in
pharmacogenetics mean that in the future, physicians may be able to use a
patients genetic information to make certain prescribing decisions for
antihypertensives.
Interactions
Specific drug references should be consulted, since interactions vary for
antihypertensive drugs.
Key Terms
- Adrenergic
- Activated by adrenalin (norepinephrine), loosely applied to the
sympathetic nervous system responses.
- Angioedema
- An allergic skin disease characterized by patches of confined
swelling involving the skin the layers beneath the skin, the mucous
membranes, and sometimes the viscera-called also angioneurotic edema,
giant urticaria, Quincke's disease, or Quincke's edema.
- Arteries
- Blood vessels that carry blood away from the heart to the cells,
tissues, and organs of the body.
- Laryngospasm
- Spasmodic closure of the larynx.
- Pregnancy category
- A system of classifying drugs according to their established risks
for use during pregnancy. Category A: Controlled human studies have
demonstrated no fetal risk. Category B: Animal studies indicate no fetal
risk, but no human studies; or adverse effects in animals, but not in
well-controlled human studies. Category C: No adequate human or animal
studies; or adverse fetal effects in animal studies, but no available
human data. Category D: Evidence of fetal risk, but benefits outweigh
risks. Category X: Evidence of fetal risk. Risks outweigh any benefits.
- Sympathetic nervous system
- The part of the autonomic nervous system that is concerned
especially with preparing the body to react to situations of stress or
emergency; it contains chiefly adrenergic fibers and tends to depress
secretion, decrease the tone and contractility of smooth muscle, and
increase heart rate.
|
