Adrenergic Drugs Health Article

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