Adrenergic Drugs

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 (dong 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.

Resources

books

Brody, T. M., J. Larner, K. P. Minneman, and H. C. Neu. Human Pharmacology: Molecular to Clinical, 2nd ed. St. Louis, MO: Mosby Year-Book, 1995.

"Drug Interactions." Section 22, Chapter 301 in The Merck Manual of Diagnosis and Therapy, edited by Mark H. Beers, MD, and Robert Berkow, MD. Whitehouse Station, NJ: Merck Research Laboratories, 1999.

Reynolds, J. E. F., ed. Martindale: The Extra Pharmacopoeia, 31st ed. London, UK: The Pharmaceutical Press, 1996.

periodicals

Brumley, Cindy, RN. "Herbs and the Perioperative Patient." AORN Journal 72 (November 2000): 785-794.

organizations

American Herbal Products Association (AHPA). 8484 Georgia Avenue, Suite 370, Silver Spring, MD 20910. (301) 588-1171. <www.ahpa.org>.

American Society of Health-System Pharmacists (ASHP). 7272 Wisconsin Avenue, Bethesda, MD 20814. (301) 657-3000. <www.ashp.org>.

United States Food and Drug Administration (FDA). 5600 Fishers Lane, Rockville, MD 20857-0001. (888) INFO-FDA. <www.fda.gov>.

other

"Adrenergic Drugs." Lutherans Online. <www.lutheransonline.com/servlet/lo_ProcServ/dbpage=page&GID=01158001360986064365619618&PG=01268001361016404720 815396>.

"Bronchodilators, Adrenergic." Medline Plus Drug Information. <www.nlm.nih.gov/medlineplus/druginfo/uspdi/202096.html>.

Samuel Uretsky, PharmD