CD-ROM Today (UK) (Spanish) 15/CDRT.iso/dp/0299/02990.txt

Text File | 1994-01-17 | 17KB | 314 lines

$Unique_ID{BRK02990}
$Pretitle{}
$Title{The New Prescription Drug Reference Guide - How Drugs Work, part I}
$Subject{Types CARDIOVASCULAR Antianginals Antiarrhythmics Antihypertensives
Diuretics Cardiac Glycosides Anticoagulants Antihyperlipidemics Vasodilators
Beta Blockers Calcium Channel Blockers EARS EYES GASTROINTESTINAL
Antinauseants Anticholinergics Antiulcer Antidiarrheals HORMONES Thyroid
Antidiabetic Steroids Sex Hormones ANTI-INFECTIVES Antibiotics Antivirals
Vaccines anthelmintics pediculicide scabicide ANTINEOPLASTICS TOPICAL CENTRAL
NERVOUS SYSTEM Sedatives Tranquilizers Antidepressants Amphetamines
Anticonvulsants Antiparkinsonism Agents Analgesics Anti-Respiratory
Antitussives Expectorants Decongestants Bronchodilators Antihistamines
VITAMINS MINERALS}
$Volume{}
$Log{}

Copyright (C) 1993 Publications International, Ltd.


How Drugs Work, part I
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Prescription drugs fall into a number of groups according to the conditions
for which they are prescribed.  In the following pages, we will provide you
with a better understanding of the types of medications that are prescribed
for different medical conditions.  We'll describe the intended actions of
drugs and the therapeutic effects you can expect from various types of
medications.

CARDIOVASCULAR DRUGS

     Antianginals

     Since the heart is a muscle that must work continuously, it requires a
constant supply of nutrients and oxygen.  The chest pain known as angina can
occur when there is an insufficient supply of blood, and consequently of
oxygen, to the heart.  There are several types of antianginal drugs.  These
drugs include vasodilators (nitroglycerin, isosorbide dinitrate), calcium
channel blockers (diltiazem, nifedipine, verapamil), and beta blockers
(acebutolol, atenolol, labetalol, metoprolol, nadolol, pindolol, propranolol,
timolol).  All of these drugs act by increasing the amount of oxygen that
reaches the heart muscle.

     Antiarrhythmics

     If the heart does not beat rhythmically or smoothly (a condition called
arrhythmia), its rate of contraction must be regulated.  Antiarrhythmic drugs
(disopyramide, mexiletine, procainamide, propranolol, tocainide, quinidine)
prevent or alleviate cardiac arrhythmias by altering nerve impulses within the
heart.

     Antihypertensives

     Briefly, high blood pressure is a condition in which the pressure of the
blood against the walls of the blood vessels is higher than what is considered
normal.  High blood pressure, or hypertension, which can eventually cause
damage to the brain, eyes, heart, or kidneys, is controllable.  If a
medication for high blood pressure has been prescribed, it is very important
that you continue to take it regularly, even if you don't notice any symptoms
of hypertension.  If hypertension is controlled, other damage can be
prevented.  Drugs that counteract or reduce high blood pressure can prolong a
hypertensive patient's life.
     Several different drug actions produce an antihypertensive effect.  Some
drugs block nerve impulses that cause arteries to constrict; others slow the
heart rate and decrease its force of contraction; still others reduce the
amount of a certain hormone (aldosterone) in the blood that causes blood
pressure to rise.  The effect of any of these is to reduce blood pressure.
The mainstay of antihypertensive therapy is often a diuretic, a drug that
reduces body fluids.  Examples of additional antihypertensive drugs include
clonidine, hydralazine, methyldopa, prazosin, and reserpine.

     Diuretics

     Diuretic drugs, such as chlorothiazide, chlorthalidone, furosemide,
hydrochlorothiazide, and spironolactone, promote the loss of water and salt
from the body (this is why they are sometimes called "water pills").  This
loss of water and salt results in lowering of blood pressure.  They also lower
blood pressure by increasing the diameter of blood vessels.  Because many
antihypertensive drugs cause the body to retain salt and water, they are often
used concurrently with diuretics.  Most diuretics act directly on the kidneys,
but there are different types of diuretics, each with different actions.
Thus, therapy for high blood pressure can be individualized for each patient's
needs.
     Thiazide diuretics, such as chlorothiazide, chlorthalidone, and
hydrochlorothiazide are the most commonly prescribed water pills available
today.  They are generally well tolerated and can be taken once or twice a
day.  Since patients do not develop a tolerance to their antihypertensive
effect, they can be taken for prolonged periods.  However, a major drawback to
thiazide diuretics is that they often deplete the body of potassium.  This
depletion can be compensated for with a potassium supplement.  Potassium-rich
foods and liquids, such as bananas, apricots, and orange juice, can also be
used to help correct the potassium deficiency.  Salt substitutes are another
source of potassium.  Your doctor will direct you as to which source of
potassium, if any, is appropriate for you to use.
     Loop diuretics, such as furosemide, act more vigorously than thiazide
diuretics.  (The term "loop" refers to the structures in the kidneys on which
these medications act.)  Loop diuretics promote more water loss but also
deplete more potassium.
     To remove excess water from the body but retain its store of potassium,
manufacturers developed potassium-sparing diuretics.  Drugs such as
spironolactone, triamterene, and amiloride are effective in treating potassium
loss, heart failure, and hypertension.  Potassium-sparing diuretics are
combined with thiazide diuretics in medications such as spironolactone and
hydrochlorothiazide combination, triamterene and hydrochlorothiazide
combination, and amiloride and hydrochlorothiazide combination.  Such
combinations enhance the antihypertensive effect and reduce the loss of
potassium.  They are now among the most commonly used antihypertensive agents.

     Cardiac Glycosides

     Cardiac glycosides include drugs that are derived from digitalis (for
example, digoxin and digitoxin).  This type of drug slows the rate of the
heart but increases its force of contraction.  Cardiac glycosides, therefore,
act as both heart depressants and stimulants and may be used to regulate
irregular heart rhythm or to increase the volume of blood pumped by the heart
in heart failure.

     Anticoagulants

     Drugs that prevent blood clotting are called anticoagulants (blood
thinners).  Anticoagulants fall into two categories.
     The first category contains only one drug, heparin.  Heparin must be
given by injection, so its use is generally restricted to hospitalized
patients.
     The second category includes oral anticoagulants, principally derivatives
of the drug warfarin.  Warfarin may be used in the treatment of conditions
such as stroke, heart disease, and abnormal blood clotting.  It is also used
to prevent the movement of a clot, which could cause serious problems.  It
acts by preventing the liver from manufacturing the proteins responsible for
blood clot formation.
     Persons taking warfarin must avoid using many other drugs (including
aspirin), because their interaction with the anticoagulant could cause
internal bleeding.  Patients taking warfarin should check with their
pharmacist or physician before using any other medications, including
over-the-counter products for coughs or colds.  In addition, they must have
their blood checked frequently by their physician to ensure that the drug is
maintaining the correct degree of blood thinning.

     Antihyperlipidemics

     Drugs used to treat atherosclerosis (arteriosclerosis, or hardening of
the arteries) act to reduce the serum (the liquified portion of blood) levels
of cholesterol and triglycerides (fats), which form plaques (deposits) on the
walls of arteries.  Some antihyperlipidemics, such as cholestyramine and
colestipol, bind to bile acids in the gastrointestinal tract, thereby
decreasing the body's production of cholesterol.  Clofibrate and probucol also
decrease the body's production of cholesterol.  Use of such drugs is generally
recommended only after diet and lifestyle changes have failed to lower blood
lipids to desirable levels.  Even then, diet therapy should be continued.

     Vasodilators

     Vasodilating drugs cause the blood vessels to dilate (widen).  Some of
the antihypertensive agents, such as hydralazine and prazosin, lower blood
pressure by dilating the arteries or veins.  Other vasodilators are used in
the treatment of stroke and diseases characterized by poor circulation.
Ergoloid mesylates, for example, are used to reduce the symptoms of senility
by increasing blood flow to the brain.

     Beta Blockers

     Beta-blocking drugs block the response of the heart and blood vessels to
nerve stimulation, thereby slowing the heart rate and reducing high blood
pressure.  They are used in the treatment of a wide range of diseases
including angina, hypertension, migraine headaches, and arrhythmias.
Propranolol and metoprolol are two examples of beta blockers.

     Calcium Channel Blockers

     Calcium channel blockers (diltiazem, nifedipine, verapamil) are used for
the prevention of angina (chest pain).  Verapamil is also useful in correcting
certain arrhythmias (heartbeat irregularities) and lowering blood pressure.
This group of drugs is thought to prevent angina and arrhythmias by blocking
or slowing calcium flow into muscle cells, which results in vasodilation
(widening of the blood vessels) and greater oxygen delivery to the heart
muscle.

DRUGS FOR THE EARS

     For an ear infection, a physician usually prescribes an antibiotic and a
steroid, or a medication that contains a combination of these.  The antibiotic
attacks the infecting bacteria, and the steroid reduces the inflammation and
pain.  Often, a local anesthetic, such as benzocaine or lidocaine, may also be
prescribed to relieve pain.

DRUGS FOR THE EYES

     Almost all drugs that are used to treat eye problems can be used to treat
disorders of other parts of the body as well.
     Glaucoma is one of the major disorders of the eye, especially in people
over 40 years of age, and results in increased pressure within the eyeball.
Although glaucoma is sometimes treated surgically, pressure in the eye can
usually be reduced, and blindness prevented, through use of eye drops.  Two
drugs frequently prescribed as eye drops are epinephrine and pilocarpine.
     Pilocarpine is a cholinergic drug.  Cholinergic drugs act by stimulating
parasympathetic nerve endings.  Stimulation of these nerve endings alters the
activity of many organs throughout the body.  For example, a cholinergic drug
can cause the heart rate to decrease, intestinal activity to increase, and the
bronchioles within the lungs to constrict.  When used in the eyes, pilocarpine
causes constriction of the pupils and increases the flow of aqueous humor
(fluid) out of the eye, thereby reducing the pressure.
     Epinephrine is a newer name for the body chemical called adrenaline.
Epinephrine is secreted in the body when one must flee from danger, resist
attack, or combat stress.  Epinephrine has adrenergic properties, such as
increasing the amount of sugar in the blood, accelerating the heartbeat, and
dilating the pupils.  The mechanism by which epinephrine lowers pressure
within the eye is not completely understood, but it appears to involve both a
decrease in the production of aqueous humor and an increase in the outflow of
this fluid from the eye.
     Antibiotics are used to treat bacterial eye infections.  Steroids can
also be used to treat noninfectious eye inflammations, as long as these
medications are not used for too long a period of time.  Pharmacists carefully
monitor requests for eye drop refills, particularly for drops that contain
steroids, and may refuse to refill such medication until you have revisited
your doctor because these products can cause further eye problems with
long-term use.

GASTROINTESTINAL DRUGS

     Antinauseants

     Antinauseants reduce the urge to vomit.  One of the most effective
antinauseants is the phenothiazine derivative prochlorperazine.  This
medication acts on the vomiting center in the brain.  It is often administered
rectally and usually alleviates nausea and vomiting within a few minutes to an
hour.  Antihistamines are also commonly used to prevent nausea and vomiting,
especially when those symptoms are due to motion sickness.  This type of
medication may also work at the vomiting center in the brain.

     Anticholinergics

     Anticholinergic drugs--for example, dicyclomine--slow the action of the
bowel and reduce the amount of stomach acid.  Because these drugs slow the
action of the bowel by relaxing the muscles and relieving spasms, they are
said to have an antispasmodic action.

     Antiulcer Medications

     Antiulcer medications are prescribed to relieve symptoms and promote
healing of peptic ulcers.  The antisecretory ulcer medications cimetidine,
famotidine, and ranitidine work by suppressing the production of excess
stomach acid.  Another antiulcer drug, sucralfate, works by forming a chemical
barrier over an exposed ulcer (like a bandage) thereby protecting the ulcer
from stomach acid.  These drugs provide sustained relief from ulcer pain and
promote healing.

     Antidiarrheals

     Diarrhea may be caused by many conditions, including influenza and
ulcerative colitis, and can sometimes occur as a side effect of drug therapy.
Narcotics and anticholinergics slow the action of the bowel and can thereby
help alleviate diarrhea.  A medication such as diphenoxylate and atropine
contains both a narcotic and an anticholinergic.

HORMONES

     A hormone is a substance produced and secreted by a gland.  Hormones
stimulate and regulate body functions.  Hormone drugs are given to mimic the
effects of naturally produced hormones.
     Hormone drugs are prescribed to treat various conditions.  Most often,
they are used to replace naturally occuring hormones that are not being
produced in amounts sufficient to regulate specific body functions.  This
category of medication also includes oral contraceptives and certain types of
drugs that are used to combat inflammatory reactions.

     Thyroid Drugs

     Thyroid hormone was one of the first hormone drugs to be produced
synthetically.  Originally, thyroid preparations were made by drying and
pulverizing the thyroid glands of animals and then forming them into tablets.
Such preparations are still used today in the treatment of patients who have
reduced levels of thyroid hormone production.  However, a synthetic thyroid
hormone (levothyroxine) is also available.

     Antidiabetic Drugs

     Insulin, which is secreted by the pancreas, regulates the level of
glucose (a form of sugar) in the blood, as well as the metabolism of
carbohydrates and fats.  Insulin's counterpart, glucagon, stimulates the liver
to release stored glucose.  Both insulin and glucagon must be present in the
right amounts to maintain the proper blood sugar levels.
     Treatment of diabetes mellitus (the condition in which the body is unable
to produce and/or utilize insulin) may involve an adjustment of diet and/or
the administration of insulin or oral antidiabetic drugs.  Glucagon is given
only in emergencies (for example, insulin shock, when blood sugar levels must
be raised quickly).
     Oral antidiabetic medications induce the pancreas to secrete more insulin
by acting on small groups of cells within the pancreas that make and store
insulin.  Oral antidiabetic medications are prescribed for diabetic patients
who are unable to regulate their blood sugar levels through diet modification
alone.  These medications cannot be used by patients who have
insulin-dependent (juvenile-onset, or Type I) diabetes; their blood sugar
levels can be controlled only with injections of insulin.

     Steroids

     The pituitary gland secretes adrenocorticotropic hormone (ACTH), which
directs the adrenal glands to produce adrenocorticosteroids (for example,
cortisone).  Oral steroid preparations (for example, prednisone) may be used
to treat inflammatory diseases such as arthritis or to treat poison ivy, hay
fever, or insect bites.  How these drugs relieve inflammation is currently
unknown.
     Steroids may also be applied to the skin to treat certain inflammatory
skin conditions.  Triamcinolone and the combination of fluocinonide,
hydrocortisone, and iodochlorhydroxyquin are examples of steroid hormone
creams or ointments.

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The material contained here is "FOR INFORMATION ONLY" and should not replace
the counsel and advice of your personal physician.  Promptly consulting your
doctor is the best path to a quick and successful resolution of any medical
problem.