Adrenergic Drugs
Definition
Adrenergic amines are drugs that
stimulate the sympathetic nervous system (also called the
adrenergic nervous system). These compounds are also called
sympathomimetic drugs. The sympathetic nervous system is the part of the
autonomic nervous system that originates in the
thoracic (chest) and lumbar (lower back) regions of the spinal cord and
regulates
involuntary reactions to stress. It stimulates the
heartbeat, sweating, breathing rate, and other stress-related body
processes.
Purpose
Adrenergic drugs have many uses. They are used to increase the output of the
heart, to raise blood pressure, and to increase
urine flow as part of the treatment of shock. Adrenergics are also used as
heart stimulants. They may be given to a patient to reverse the drop in blood
pressure that is sometimes caused by
general anesthesia. They may be used to stop bleeding by causing the blood
vessels to
constrict, and to keep local anesthetics in a small area of the body by
closing off the nearby blood vessels that would otherwise spread the
anesthetic to other parts of the body. This ability to make blood vessels
constrict makes adrenergics useful in reducing nasal stuffiness associated with
colds and
allergies. They may also be given to open the bronchi (the tubes leading to
the lungs) for treatment of
asthma and
chronic obstructive pulmonary disease (COPD).
Description
There are several types of adrenergic receptors in the human body. Although
all types of adrenergic receptors (nerve endings) respond to the same drugs, the
effects depend on which specific receptors are stimulated. The alpha receptors
make the heart beat faster, the pupils of the eyes dilate, and the muscles
contract. The beta receptors have similar effects and also cause the bronchi in
the lungs to open up. Both alpha and beta receptors are divided into
subgroups�alpha-1, alpha-2, beta-1, and beta-2�each with its own specific
effects. A hormone called norepinephrine that is secreted in the body affects
all types of adrenergic receptors; the drugs used in medicine and surgery,
however, have been developed to affect only specific types of receptors.
There are several adrenergic amines in common use:
- Albuterol (Alupent, Ventolin, others): given by mouth or as a nasal
spray to improve breathing.
- Dobutamine (Dobutrex and generic forms): used to stimulate the heart
during surgery or after a heart attack or cardiac arrest.
- Dopamine (Intropin): used to increase cardiac output, blood pressure,
and urine flow in treating patients with shock.
- Epinephrine (Adrenalin): used locally to control bleeding from
arterioles and
capillaries during surgery. It is used to treat shock, as a heart
stimulant, and as a
decongestant. Epinephrine may be added to local anesthetics to keep the
anesthetic in the area where it is applied. Epinephrine may also be applied
to the eye to reduce the symptoms of conjunctivitis (red eye).
- Isoproteranol: most widely used to ease breathing problems in asthma and
COPD, but also used to control several types of irregular heartbeat until a
pacemaker can be
implanted.
- Phenylephrine (Neo-Synephrine): used to treat shock and low blood
pressure; also used in the form of nose drops or spray to relieve nasal
congestion from colds and allergies.
- Metaraminol (Aramine): used to raise the blood pressure and stimulate
the heart in treating patients with shock.
- Norepinephrine (Levophed): used to increase the output of the heart and
raise blood pressure as part of the treatment of shock.
Recommended Dosage
The recommended
dosage of an adrenergic drug depends on the specific compound, the purpose
for which it is given, and the route of administration (oral or
intravenous).
People who use adrenergic amines to treat breathing problems or
conjunctivitis (red eye) should not use over-the-counter preparations of these
drugs as an alternative to seeking professional care. These medications may
temporarily relieve the symptoms of some disorders but will not cure the
underlying problems, which may be serious.
Precautions
When adrenergic amines are given during surgery, they will be administered by
an anesthesiologist or other health care professional skilled in their use. It
is the anesthesiologist's responsibility to exercise appropriate care when these
drugs are used during an operation.
The following are some of the hazards associated with the use of adrenergic
amines. Patients under
anesthesia may not be aware of these side effects:
- nervousness
- rapid heart beat
- high blood pressure
- irregular heart beat
- rapid heartbeat
- chest pain
- dizziness
- dry mouth
- headache
- flushing
- nausea
- vomiting
- weakness
Before undergoing procedures that may involve the use of an
adrenergic amine, people with any of these medical problems should make sure
their physicians know about them:
- narrow-angle glaucoma
- liver disease
- enlarged heart
- disorders affecting the
arteries and veins
- diseases and disorders affecting the blood supply to the brain
Side Effects
The most common side effects of adrenergic amines are nervousness,
agitation, and wakefulness. These side effects do not usually cause problems
when the drugs are given during surgery or in combination with local
anesthetics.
The following side effects sometimes occur when adrenergic amines are used to
treat nasal congestion due to allergies or infections:
- rapid heartbeat
- increased sweating
- nervousness
- hallucinations
- sleep disturbances
- paleness
Other rare side effects may occur. Anyone who has unusual symptoms after
taking adrenergic amines should contact his or her physician right away.
Interactions
Adrenergic amines may interact with many different types of drugs. People
should discuss the use of these drugs with their pharmacist or physician before
using over-the-counter preparations that contain them for colds or allergies.
Patients scheduled for surgery should be sure to give the surgeon and
anesthesiologist a list of all the drugs they take, including
nonprescription, herbal, and alternative preparations. Some drugs that
interact with adrenergic amines should be discontinued several days before
surgery, since they last for a long time after the last dose.
Drugs that may interact with adrenergic amines include:
- furazolidone (Furoxone)
- tricyclic
antidepressants (Adapin, Asendin, Aventyl, Elavil, Endep, Norpramin,
Pamelor, Sinequan, Surmontil, Tofranil, Vivactil)
- guanethidine (Ismelin)
- methyldopa (Aldomet)
Herbs that have been reported to interact with adrenergic amines include
ephedra (ma huang), often sold in over-the-counter weight loss formulas; St.
John's
wort, a popular
remedy for
anxiety or depression;
alfalfa; hibiscus;
ginseng; angelica (ong
quai); and
yohimbe.
The list above does not include every drug or herb that may interact with
adrenergic amines. People should consult their physician or pharmacist before
combining adrenergic amines with any other
prescription or nonprescription (over-the-counter) medicine.
