Adrenergic drugs are also called adrenergic amines or sympathomimetic drugs. They are medicines that work by stimulating the sympathetic nervous system (SNS). The SNS is part of the automatic nervous system (ANS). It helps to regulate your body’s reaction to stress or an emergency. During these times, the SNS releases chemicals called neurotransmitters from the adrenal gland. These chemicals act on your body to increase heart rate, sweating, and breathing rate, and decrease digestion. The response by your body is sometimes called the “fight or flight” response.
Adrenergic drugs stimulate the same nerves by either mimicking the action of the neurotransmitter norepinephrine or stimulating its release. They are used for many life-threatening conditions. These include cardiac arrest, shock, or opening the airways during an asthma attack or allergic reaction.
Adrenergic drugs stimulate the adrenergic nerves. The structures of the drugs closely resemble the neurotransmitters that your body produces during times of stress, such as norepinephrine. Norepinephrine acts directly on the adrenergic receptors. Therefore, adrenergic drugs are able to interact with the same receptor sites as the neurotransmitter.
There are several types of adrenergic receptors in the body. The specific action of the drug depends on which type of the adrenergic receptor is affected. It also depends on whether or not the drug acts directly on the receptor or indirectly by stimulating the release of neurotransmitters. The receptors include:
Examples of the affects adrenergic drugs can have on the body include:
- increasing blood pressure
- constricting blood vessels
- opening the airways leading to the lungs
- increasing heart rate
- stopping bleeding
Adrenergic drugs have been developed to act on specific receptors in the body. The condition they are used to treat depends on which receptor is affected by the drug. Examples of some broad types of adrenergic drugs and their uses include:
Bronchodilators act on the beta-receptors directly to improve breathing in patients with respiratory diseases like asthma, chronic obstructive pulmonary disease (COPD), emphysema, and bronchitis. They open up the bronchial tubes, or air passages. Examples of adrenergic drugs used for bronchodilation include:
- Pirbuterol (NIH)
This list is not all-inclusive.
Sometimes an allergic reaction to insect stings, foods, or other substances can cause swelling that tightens up the air passages. Epinephrine can be injected in these emergency situations to open up the airways.
Vasopressors can act on the alpha-1, beta-1, and beta-2 adrenergic receptors. They also act on dopamine receptors. They can act on more than one type of receptor at the same time. Examples of these types of adrenergic drugs include:
- Pseudoephedrine (Sudafed)
- Oxymetazoline (Elmhurst)
The vasopressors stimulate smooth muscle contraction of the blood vessels. The blood vessels are the part of the circulatory system that moves blood around the body. The muscle contraction leads to vasoconstriction. Vasoconstriction is the narrowing of the blood vessels. The narrowing of the blood vessels will cause a rise in blood pressure.
The increased blood pressure can be used to treat patients with shock. Constriction of the blood vessels can also be useful to stop bleeding as well as to keep anesthetics to a specific area of the body. They do this by closing off nearby blood vessels to keep the anesthetic from spreading.
Drugs in this class may also be used when swelling of the blood vessels in the mucous membranes of the nose blocks up the nasal passage and causes discharge. This might happen if you have a cold or allergies. Adrenergic drugs can act on sympathetic nerves to shrink the swollen membranes and provide relief for a few hours. These drugs are often referred to as nasal decongestants.
Adrenergic drugs are also used to stimulate and restore the heart beat if a person’s heart stops beating. This might occur due to drowning, electrocution, suffocation, or other causes. Epinephrine, for example, can be injected directly into the heart to make the heart start beating again.
The FDA approved label for epinephrine states that the drug should be used with caution in people with heart disease, cardiac arrhythmias, or hypertension (FDA).
You should tell your doctor if you are taking any other prescription or over-the-counter drugs.
Side effects depend on which adrenergic drug you are taking.
Common side effects of adrenergic drugs, like epinephrine, include:
- restlessness or wakefulness