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Copyright (C) 1991 Publications International, Ltd.


How Drugs Work
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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
occurs when there is an insufficient supply of blood, and consequently of
oxygen, to the heart.  There are several types of antianginal drugs.  These
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
effectively 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, methyclothiazide, 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,
hydrochlorothiazide, and methyclothiazide, 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 therapy 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 occurring 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 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.

     Sex Hormones

     Although the adrenal glands secrete small amounts of sex hormones, these
hormones are produced mainly by the sex glands.  Estrogens are the female
hormones responsible for secondary sex characteristics such as development of
the breasts and maintenance of the lining of the uterus.  Testosterone
(androgen) is the corresponding male hormone.  It is responsible for secondary
sex characteristics such as a beard, a deepened voice, and the maturation of
external genitalia.  Progesterone is also produced in females--it prepares the
uterus for pregnancy.
     Testosterone reduces elimination of protein from the body, thereby
producing an increase in muscle size.  Athletes sometimes take drugs called
anabolic steroids (chemicals similar to testosterone) for this effect, but
such use of these drugs is dangerous.  Anabolic steroids can adversely affect
the heart, nervous system, and kidneys.
     Most oral contraceptives (birth control pills) combine estrogen and
progesterone, but some contain only progesterone.  The estrogen in birth
control pills prevents egg production.  Progesterone aids in preventing
ovulation, alters the lining of the uterus, and thickens cervical
mucus--processes that help to prevent conception and implantation.  Oral
contraceptives have many side effects, so their use should be discussed with a
physician.
     Conjugated estrogens are used as replacement therapy to treat symptoms of
menopause in women whose bodies are no longer producing sufficient amounts of
estrogen.  Medroxyprogesterone is used to treat uterine bleeding and menstrual
problems.  It prevents uterine bleeding by inducing and maintaining a lining
in the uterus that resembles the lining produced during pregnancy.  In
addition, it suppresses the release of the pituitary gland hormone that
initiates ovulation.

ANTI-INFECTIVES

     Antibiotics

     Antibiotics are used to treat a wide variety of bacterial infections.
They are usually derived from molds or are produced synthetically.
Antibiotics inhibit the growth of bacteria by interfering with their
production of certain biochemicals necessary to sustain life or by interfering
with their ability to use available nutrients.  The body's natural defenses
then have a much easier time eliminating the infection.
     When used properly, antibiotics are usually effective.  To adequately
treat an infection, antibiotics must be taken regularly for a specific period
of time.  If you do not take an antibiotic for the prescribed period,
microorganisms resistant to the antibiotic are given the opportunity to
continue growing, and your infection could recur.  Aminoglycosides,
cephalosporins, erythromycins, penicillins (including ampicillin and
amoxicillin), and tetracyclines are some examples of antibiotics.
     Antibiotics do not counteract viruses, such as those causing the common
cold, so their use in cold therapy is inappropriate.

     Antivirals

     Antiviral drugs are used to combat viral infections.  An antiviral drug
called acyclovir is being used in the management of herpes.  Acyclovir reduces
the reproduction of the herpes virus in initial outbreaks, lessens the number
of recurring outbreaks, and speeds the healing of herpes blisters.  However,
this antiviral drug does not cure herpes.

     Vaccines

     Vaccines were used long before antibiotics became available.  A vaccine
contains weakened or dead disease-causing microorganisms or parts of such
organisms, which activate the body's immune system to produce a natural
defense against a particular disease (such as polio or measles).  A vaccine
may be used to alleviate or treat an infectious disease, but most commonly it
is used to prevent a specific disease.

     Other Anti-infectives

     Drugs called anthelmintics are used to treat worm infestations.  Fungal
infections are treated with antifungals (such as nystatin)--drugs that destroy
and prevent the growth of fungi.
     A pediculicide is a drug used to treat a person infested with lice, and a
scabicide is a preparation used to treat a person with scabies.

ANTINEOPLASTICS

     Antineoplastic drugs are used in the treatment of cancer.  Most of the
drugs in this category prevent the growth of rapidly dividing cells, such as
cancer cells.  Antineoplastics are, without exception, extremely toxic and can
cause serious side effects.  But for many cancer victims, the benefits derived
from chemotherapy with antineoplastic drugs far outweigh the risks involved.

TOPICAL DRUGS

     Drugs are often applied topically (locally to the skin) to treat skin
disorders with minimal systemic (throughout the body) side effects.
Antibiotic creams or ointments are used to treat skin infections, and
adrenocorticosteroids are used to treat inflammatory skin conditions.  Another
common dermatologic (skin) problem is acne.  Acne can be--and often
is--treated with over-the-counter drugs, but it sometimes requires
prescription medication.  Antibiotics such as tetracycline, erythromycin, or
clindamycin are used orally or applied topically to slow the growth of the
bacteria that play a role in the formation of acne pustules.  Keratolytics
(agents that soften the skin and cause the outer cells to slough off) are also
sometimes prescribed.
     Some drugs applied to the skin do have effects within the body.  For
example, nitroglycerin is absorbed into the bloodstream from ointment or
patches placed on the skin.  The absorbed nitroglycerin dilates blood vessels
and prevents anginal pain.  Clonidine, scopolamine, and estrogen are available
as transdermal patches, also.

CENTRAL NERVOUS SYSTEM DRUGS

     Sedatives

     Medications used in the treatment of anxiety or insomnia selectively
reduce activity in the central nervous system (brain and spinal cord).  Drugs
that have a calming effect include barbiturates, chlordiazepoxide,
clorazepate, diazepam, doxepin, hydroxyzine, meprobamate, and oxazepam.  Drugs
to induce sleep in insomniacs include butabarbital, flurazepam, temazepam, and
triazolam.

     Tranquilizers

     Major tranquilizers or antipsychotic agents are usually prescribed for
patients with psychoses (certain types of mental disorders).  These drugs calm
certain areas of the brain but permit the rest of the brain to function
normally.  They act as a screen that allows transmission of some nerve
impulses but restricts others.  The drugs most frequently used are
phenothiazines, such as chlorpromazine and thioridazine.  Haloperidol, a
butyrophenone, has the same effect as chlorpromazine.

     Antidepressants

     Tricyclic antidepressants (such as amitriptyline), tetracyclic
antidepressants (such as maprotiline), and monoamine oxidase (MAO) inhibitors
(such as phenelzine) are used to combat depression.  Antidepressants are also
used in the preventive treatment of migraine headaches, although the manner in
which they help these headaches is not clearly understood.
     Antidepressants may produce serious side effects, and they can interact
with other drugs.  MAO inhibitors can also interact with certain foods,
resulting in dangerous increases in blood pressure.  Therefore, they should be
used very carefully.

     Amphetamines

     Amphetamines or adrenergic drugs are commonly used as anorectics (drugs
used to reduce the appetite).  These drugs temporarily quiet the part of the
brain that causes hunger, but they also keep a person awake, speed up the
heart, and raise blood pressure.  After two to three weeks, these medications
begin to lose their effectiveness as appetite suppressants.
     Amphetamines stimulate most people, but they have the opposite effect on
hyperkinetic children.  Hyperkinesis (the condition of being highly
overactive) is difficult to diagnose or define and requires a specialist to
treat.  When hyperkinetic children take amphetamines or the adrenergic drug
methylphenidate, their activity slows down.  Why amphetamines affect
hyperkinetic children in this way is unknown.  Most likely, they quiet these
youngsters by selectively stimulating parts of the brain that ordinarily
provide control of activity.

     Anticonvulsants

     Drugs such as phenytoin and phenobarbital are used to control seizures
and other symptoms of epilepsy.  They selectively reduce excessive stimulation
in the brain.

     Antiparkinsonism Agents

     Parkinson's disease is a progressive disorder that is due to a chemical
imbalance in the brain.  Victims of Parkinson's disease have uncontrollable
tremors, develop a characteristic stoop, and eventually become unable to walk.
Drugs such as benztropine, trihexyphenidyl, levodopa, and bromocriptine are
used to correct the chemical imbalance, thereby relieving the symptoms of the
disease.  Benztropine and trihexyphenidyl are also used to relieve tremors
caused by other medications.

     Analgesics

     Pain is not a disease but a symptom.  Drugs used to relieve pain are
called analgesics.  These drugs form a rather diverse group.  We do not fully
understand how most analgesics work.  Whether they all act on the brain is not
known.  Analgesics fall into two categories; they may be either narcotic or
nonnarcotic.
     Narcotics are derived from the opium poppy.  They act on the brain to
cause deep analgesia and often drowsiness.  Some narcotics relieve coughing
spasms and are used in many cough syrups.  Narcotics relieve pain and give the
patient a feeling of well-being.  They are also addictive.  Manufacturers have
attempted to produce nonaddictive synthetic narcotic derivatives but have not
yet been successful.
     Many nonnarcotic pain relievers are commonly used.  Salicylates are the
most commonly used pain relievers in the United States today.  The most widely
used salicylate is aspirin.  While aspirin ordinarily does not require a
prescription, many doctors may prescribe it to treat such diseases as
arthritis.
     The aspirin substitute acetaminophen may be used in place of aspirin to
relieve pain.  It does not, however, reduce inflammation (such as that caused
by arthritis).
     A number of analgesics contain codeine or other narcotics combined with
nonnarcotic analgesics (such as aspirin or acetaminophen).  These analgesics
are not as potent as pure narcotics but are frequently as effective.  Because
these medications contain narcotics, they have potential for abuse and must be
used with caution.

     Anti-inflammatory Drugs

     Inflammation is the body's response to injury.  It causes swelling, pain,
fever, redness, and itching.  Aspirin is one of the most effective
anti-inflammatory drugs.  Other drugs, called nonsteroidal antiinflammatory
drugs (for example, fenoprofen, ibuprofen, indomethacin, naproxen, and
tolmetin), relieve inflammation and may be more effective than aspirin in
certain individuals.  Steroids are also used to treat inflammatory diseases.
     When sore muscles tense, they cause pain, inflammation, and spasm.
Skeletal muscle relaxants (for example, orphenadrine, aspirin, and caffeine
combination; meprobamate and aspirin combination; and chlorzoxazone and
acetaminophen combination) can relieve these symptoms.  Skeletal muscle
relaxants are often given in combination with an anti-inflammatory drug such
as aspirin.  Some doctors, however, believe that aspirin and rest are better
for alleviating the pain and inflammation of muscle strain than are skeletal
muscle relaxants.


RESPIRATORY DRUGS

     Antitussives

     Antitussives control coughs.  There are numerous over-the-counter
(nonprescription) antitussives available--most of them contain
dextromethorphan.  Codeine is a narcotic antitussive that is an ingredient in
many prescription cough medications.  These cough syrups must be absorbed into
the blood and must circulate and act on the brain before they relieve a cough;
they do not "coat" the throat.

     Expectorants

     Expectorants are used to change a nonproductive cough to a productive one
(one that brings up phlegm).  Expectorants are supposed to increase the amount
of mucus produced.  However, drinking water or using a vaporizer or humidifier
is probably more effective in increasing mucus production.  Popular
expectorant ingredients include ammonium chloride, guaifenesin, potassium
guaiacolsulfonate, and terpin hydrate.

     Decongestants

     Decongestants constrict blood vessels in the nose and sinuses to open up
air passages.  They are available as oral preparations, nose drops, and nose
sprays.  Oral decongestants are slow-acting but do not interfere with
production of mucus or movement of the cilia (special hair-like structures) of
the respiratory tract.  They can, however, increase blood pressure, so they
should be used cautiously by patients with high blood pressure.  Topical
decongestants (nose drops or spray) provide almost immediate relief.  They do
not increase blood pressure as much as oral decongestants, but they do slow
the movement of the cilia.
     People who use these products may also develop a tolerance for them.
Tolerance can be described as a need for ever-increasing dosages to achieve a
beneficial effect.  The additional disadvantage of developing tolerance is
that the risk of side effects increases as the dosage increases.
Consequently, topical decongestants should not be used for more than a few
days at a time.

     Bronchodilators

     Bronchodilators (agents that open airways in the lungs) and agents that
relax smooth-muscle tissue (such as that found in the lungs) are used to
improve breathing.  Theophylline and aminophylline are oral bronchodilators
commonly used to relieve the symptoms of asthma and pulmonary emphysema.
Albuterol and metaproterenol are inhalant bronchodilators, which act directly
on the muscles of the bronchi (breathing tubes).

     Antihistamines

     Histamine is a body chemical that, when released in the body, typically
causes swelling and itching.  Antihistamines counteract these symptoms of
allergy by blocking the effects of histamine.  For mild respiratory allergies,
such as hay fever, antihistamines can be used.  Diphenhydramine and other
antihistamines are relatively slow-acting.  Severe allergic reactions
sometimes require the use of epinephrine (which is not an antihistamine); in
its injectable form, it is very fast-acting.
     Some antihistamines are also used to prevent or treat the symptoms of
motion sickness.  Diphenhydramine and meclizine are examples of drugs used for
this purpose.

VITAMINS AND MINERALS

     Vitamins and minerals are chemical substances that are vital to the
maintenance of normal body function.  Most people obtain enough vitamins and
minerals in their diet, but some people have vitamin deficiencies.  Serious
nutritional deficiencies lead to diseases such as pellagra and beriberi, which
must be treated by a physician.  People who have an inadequate or restricted
diet, people who have certain disorders or debilitating illnesses, and women
who are pregnant or breast-feeding are among those who may benefit from taking
supplemental vitamins and minerals.  However, even these people should consult
a doctor to see if a true vitamin deficiency exists.

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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.
