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Sympathomimetic Stimulant Medications

Sympathomimetic medications include epinephrine-like medications (Adrenalin,® ß2-agonists) which stimulate biochemical changes (i.e. increased cellular cyclic-AMP) in the airway which leads to bronchodilation and quick relief of asthmatic symptoms.

SYNTHETIC EPINEPHRINE MEDICATIONS

Introduction:
Epinephrine is a hormone produced by the adrenal glands (located above the kidneys within the abdomen). The adrenal glands naturally release a very small amount of this substance that may bind to specialized ß2 receptors in the lungs. These receptors, in turn, are responsible for bronchodilation (relaxing of bronchial tube constriction). In addition to its function as a powerful bronchodilator, epinephrine also can stimulate the heart to beat faster and elevate the blood pressure through binding to ß1 receptors located in heart tissue and alpha receptors in blood vessels.

If you are asthmatic, you may have a deficiency (defect) in the biochemistry of your ß2 receptors (sites on cells which need to be stimulated to cause bronchodilation). Therefore the amount of natural epinephrine that you produce may be insufficient to promote adequate stimulation and bronchodilation. Sympathomimetic medications (i.e. inhaled or injected epinephrine-like medications) can provide quick relief and allow you to overcome your defective or insensitive receptor mechanism. These medications result in bronchodilation and relieve symptoms. Quick acting sympathomimetics are "reliever" medications. Sympathomimetic medications include Adrenalin® and the more specific ß2 stimulants (agonists) discussed below.

Description:
Synthetic versions of epinephrine are considered among the most valuable medications for emergency treatment of severe, life-threatening asthmatic attacks. They may be injected or inhaled and work quickly, often reversing bronchospasm within minutes. Epinephrine medications have many uses including the following: 1) treatment of severe allergic reactions (including anaphylactic shock); 2) prolongation of the effects of local anesthetics like those used for dental procedures; and 3) stimulation of the heart.

Examples of epinephrine medications include:

• Most over-the-counter "asthma inhalers" (such as Primatene® Mist)
• Epinephrine injections administered in emergency rooms, hospitals and doctors' offices for acute asthmatic attacks
• Self administered epinephrine injections (EpiPen®) for treatment of acute outpatient allergic reactions such as anaphylactic reactions due to bee stings, food allergens, drug reactions and/or severe asthmatic attacks

Use:
Since these medications work so quickly, they are commonly used as injections as described above.While epinephrine medications are available in inhaler form in non-pre-scription preparations (Primatene® Mist), The Asthma Center specialists do not recommend these inhalers (see precautions noted below).

Risks and Precautions:
Although epinephrine is a good bronchodilator with rapid onset of action, significant side effects may occur. Epinephrine medications may cause tremor, palpitations, irritability, restlessness and possibly nausea. These preparations should be used with caution in the elderly. You should also be cautious if you have hyperthyroidism, heart disease and/or high blood pressure. These medications absolutely should be avoided if you are receiving monoamine oxidase inhibitors (MAOs) in psychiatric treatment.

The Asthma Center specialists do not recommend over-the-counter epinephrine inhalers because they are short acting and are more likely to cause heart stimulation. Overuse of those medications is very dangerous.

Epinephrine for Injection (Self Administration)

Epinephrine medications are dispensed if you are at particularly high risk for a severe asthmatic attack that might not respond to inhaler or nebulizer treatment. In this form of administration, the medication is injected subcutaneously or intramuscularly and will definitely get into you no matter how badly your lungs are obstructed. Injected epinephrine in any form can be a lifesaver since it can buy you enough time to be safely transported to the emergency room.

EpiPen® and EpiPen Jr® (a smaller dose for children) are auto-injector devices preloaded with epinephrine and can be used as emergency medications during a severe acute episode of asthma that is not responding to treatment with an inhaler or nebulizer. Epinephrine can be administered in a preloaded, premeasured dose syringe in which you manually inject epinephrine. Epinephrine also can be drawn up from a medication vial, and you can inject a specified dose. Any of these methods will be equally effective. The choice of which product will be recommended depends on your needs. Side effects of epinephrine injections usually last less than an hour or two and are similar in nature, but more intense, than those described below with the use of inhaled ß2-agonists (sympathomimetics).

Frequent use of over-the-counter epinephrine inhalers (e.g. Primatene® Mist) or prescribed epinephrine-like inhalers (e.g. albuterol, Ventolin,® Proventil®) or need for frequent epinephrine injections is usually a clear sign of poor asthma control.

ß2-AGONISTS (BETA-2 RECEPTOR STIMULATORS)

Description:
ß2-agonists are very similar to epinephrine medications. By selectively stimulating ß2 receptors, these preparations dilate or relax your spastic or constricted airways. The major advantage of these medications over synthetic epinephrine is that they primarily stimulate the bronchial tubes (via ß2 receptors). These medications also cause much less stimulation to the heart (via ß1 receptors) and to the blood vessels which can result in rapid heartbeat and/or elevated blood pressure (stimulation of alpha receptors).

ß2-agonists (beta-2 stimulators) include:

• metaproterenol (Alupent®)
• albuterol (AccuNeb,® Proventil,® Ventolin,® Xopenex®), terbutaline (Brethine,® Bricanyl®) and pirbuterol (Maxair™ Autohaler™)
• salmeterol (Serevent®) and formoterol (Foradil®) are long acting; Formoterol (Foradil®) has a faster onset than salmeterol (Serevent®)

The above two groups are more selective bronchodilators than metaproterenol and have less effect on the heart. Tremors may still occur with these medications, but they may subside with time. These preparations are available in liquid and tablet forms, metered-dose inhalers (Proventil,® Ventolin,® Serevent,® Maxair™ Autohaler,™ Foradil® Aerolizer®), inhaled powders (Serevent Diskus®) and nebulizer solutions (AccuNeb,® Proventil,® Ventolin,® Xopenex®). Tables 8, 9 and 10 below show the different types of these medications.

Please note: Serevent® and Foradil® should not be used more than twice a day since they are long acting. Therefore, the use of a short acting bronchodilator (NOT Serevent® or Foradil®) is recommended to treat a sudden onset of asthmatic symptoms.

TABLE 8

Short Acting ß2-Agonists (Sympathomimetics)

* See page 39 for more information about nebulized solutions
** Concentration depends on age and size of individual
Note: MDI = metered-dose inhaler; mcg = microgram; mg = milligram; mL = milliliter

TABLE 9

Short Acting ß2-Agonists (Sympathomimetics)

Note: mcg = microgram
*Dry Powder Inhaler

Table 10

Nebulizers (ß2 and Other Type Solutions)

For Adults: 1-2 unit doses (1.25mg/3mL) nebulized solution up to 4x/day
Note: mg = milligram; mL = milliliter

Use:
Although some of these medications are available as injections (terbutaline), The Asthma Center specialists usually recommend administration of ß2-agonist medications by inhalation (MDI or DPI). Occasionally the liquid or tablet forms of these medications are recommended when an inhaler or nebulizer cannot be used effectively. A spacer device or holding chamber is often used with a metered-dose inhaler for better delivery.

Serevent® and Foradil® are available as dry powder inhalers.

Risks and Precautions:
Side effects from these medications include:

• Palpitations (racing or pounding heartbeat)
• Headache
• Nausea
• Irritability
• Tremors

Overuse of these medications (inhaler abuse) is extremely dangerous and a sign of poor asthma management.

The Asthma Center specialists have seen individuals with a history of using a complete ß2-agonist inhaler in a single day. Most ß2-agonist metered-dose inhalers contain 200 inhalations, and in order to empty one in a single day, these individuals must have used their inhalers nearly every few minutes. Extreme overuse may lead to a situation of false confidence due to a limited short term relief while, in fact, there is a gradual worsening of the asthmatic state and risk of heart toxicity from the medication. If you use your ß2-agonist inhaler this way, you may no longer respond to the inhaler and may suddenly develop severe respiratory distress. Such a situation can result in death in spite of emergency treatment. Overuse of ß2-agonist metered-dose inhalers usually means that you have put off appropriate treatment for too long. If you use this type of inhaler more than 5 - 6 times per day or on average more than one inhaler per month, you should discuss your asthma management with your physician. These bronchodilators have little or no anti-inflammatory activity. Therefore, they offer only temporary relief from symptoms and do not correct the underlying problem of inflammation. Use of a ß2-agonist more than 3 times a week indicates the need for an anti-inflammatory controller medication.

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