Bronchodilators (Drug Class)

Bronchodilators are medications that open (dilate) the airways (bronchial tubes) of the lung by relaxing bronchial muscles and allow people who have difficulty breathing to breath better. Bronchodilators are used for treating:

• Asthma
• Chronic obstructive pulmonary disease (COPD
• Allergic reactions
• Related conditions that cause breathing problems

Asthma is a breathing problem resulting from narrowing of the airways that allow air to move in and out of the lungs. These airways become narrowed from the accumulation of mucus, spasm of the muscles that surround these airways (bronchospasm), or swelling of the lining of the airways. Airway narrowing leads to symptoms of asthma which include:

• Shortness of breath
• Wheezing
• A cough
• Congestion

The bronchodilators listed in this article are used for managing bronchospasm due to asthma, reactive airway disease, and exercise-induced asthma.

• Short-acting beta-adrenergic bronchodilators and ipratropium work quickly and are used for acute management of asthma episodes.
• Long-acting beta-adrenergic bronchodilators, tiotropium, and theophylline are used daily and long-term for preventing asthma attacks or reducing the frequency of symptoms.

The three types of bronchodilators used for treating asthma are; 1) beta-adrenergic bronchodilators; 2) anticholinergic bronchodilators; and 3) xanthine derivatives.

1. Beta-adrenergic bronchodilators dilate bronchial airways by relaxing the muscles that surround the airways. Beta-adrenergic bronchodilators are beta-2 agonists. These medications stimulate beta-2 receptors on the smooth muscle cells that line the airways, causing these muscle cells to relax, thus, opening airways.
2. Anticholinergic bronchodilators block the effect of acetylcholine on airways and nasal passages. Acetylcholine is a chemical that nerves use to communicate with muscle cells. In asthma, cholinergic nerves going to the lungs cause narrowing of the airways by stimulating muscles surrounding the airways to contract. The "anticholinergic" effect of anticholinergic bronchodilators blocks the effect of cholinergic nerves, causing the muscles to relax and airways to dilate.
3. Xanthine derivatives open airways by relaxing the smooth muscles in the walls of the airways and they also suppress the response of the airways to stimuli. The mechanism of action of xanthines is not fully understood. Xanthine derivatives may dilate bronchi by blocking the action of phosphodiesterase (PDE) enzymes which ultimately leads to increased concentration of chemicals that dilate bronchial airways.

Short-acting beta-adrenergic bronchodilator inhalers available in the US

• albuterol (AccuNeb, Proair HFA, Proventil HFA, Ventolin HFA)
• levalbuterol (Xopenex HFA)
• epinephrine injection

Long-acting beta-adrenergic bronchodilator asthma inhalers available in the US

• salmeterol (Servant Diskus)
• formoterol (Perforomist)

Anticholinergic bronchodilators available in the US

• ipratropium (Atrovent HFA)
• tiotropium (Spiriva Respimat)

Examples of xanthine derivatives available in the US

• theophylline (Theo 24, Elixophyllin, Uniphyl)
• aminophylline

Side effects of bronchodilators vary depending on the type of bronchodilator.

Beta-adrenergic bronchodilators side effects

Common side effects of beta-adrenergic bronchodilators include:

• Migraine headaches
• Non-migraine headaches
• Nausea
• Stomach upset
• Flu-like symptoms
• Cold symptoms
• Ear infections (otitis media)
• Bronchitis
• Cough

Other side effects of beta-adrenergic bronchodilators include:

• Allergic reactions (rash, hives, itching)
• Nervousness
• Tremor
• Wheezing
• Increased sputum
• Shortness of breath

Possible serious side effects of beta-adrenergic bronchodilators include:

• Bronchospasm (worsening of asthma)
• Serious allergic reactions (anaphylaxis)
• Low potassium
• Abnormal heart rhythm (palpitations)
• Fast heart rate
• Elevated blood pressure
• Chest pain

Anticholinergic bronchodilators side effects

Common side effects of anticholinergic bronchodilators include:

• Dry mouth
• Cough
• Headache
• Nausea
• Dizziness
• Difficulty breathing

Other side effects of anticholinergic bronchodilators include:

• Rash
• Itching
• Flu-like symptoms
• Indigestion
• Back pain
• Sinusitis
• Bronchitis

Possible serious side effects of anticholinergic bronchodilators include:

• Life-threatening bronchospasms
• Serious allergic reactions involving the closure of the airways.
• Worsening symptoms of benign prostatic hyperplasia
• Worsening symptoms of narrow-angle glaucoma

Xanthines side effects

Common side effects of xanthines include:

• Nausea
• Vomiting
• Diarrhea
• Headaches
• Irritability
• Flushing
• Palpitations

Other side effects of xanthines include:

• Diuresis
• Restlessness
• Tremor
• Insomnia

Possible serious side effects of xanthines include:

• Seizures
• Shock
• Heart arrhythmias
• Hypotension
• Exfoliative dermatitis

Drug interactions of beta-adrenergic bronchodilators

• Tricyclic antidepressants, for example, amitriptyline (Elavil, Endep), and monoamine oxidase inhibitors (MAOIs), for example, tranylcypromine, should not be combined with beta-adrenergic bronchodilators because of their additive effects on the vascular system (for example, increased blood pressure and/or heart rate). A period of two weeks should elapse between treatment with beta-adrenergic bronchodilators and tricyclic antidepressants or monoamine oxidase inhibitors.
• Use of beta-adrenergic bronchodilators with other stimulant medications is discouraged because of their combined effects on heart rate, blood pressure, and the potential for causing chest pain in patients with underlying coronary heart disease.
• Beta-blockers, for example, propranolol (Inderal, Inderal LA), block the effect of beta-adrenergic bronchodilators and may induce bronchospasm in asthmatics.
• Beta-adrenergic bronchodilators may cause hypokalemia (low potassium). Therefore, combining beta-adrenergic bronchodilators with loop diuretics, for example, furosemide (Lasix), may increase the likelihood of hypokalemia.

Drug interactions of anticholinergic bronchodilators

• Use with other anticholinergic drugs (for example, atropine) may increase the occurrence of side effects.

Drug interactions of xanthine bronchodilators

• Allopurinol (Zyloprim), cimetidine (Tagamet), ciprofloxacin (Cipro), clarithromycin (Biaxin), itraconazole (Sporanox), ketoconazole, erythromycin, oral contraceptives, fluvoxamine (Luvox), ephedrine, and propranolol (Inderal) elevate theophylline blood levels and can lead to toxicity. Theophylline toxicity causes nausea, vomiting, insomnia, seizures, agitation, and life- threatening heart rhythm abnormalities.
• St. John's Wort, rifampin, and carbamazepine decrease levels of theophylline and potentially its effect by increasing its elimination.
• Theophylline may decrease levels and the effect of carbamazepine by increasing its elimination. Theophylline is metabolized mainly by the liver and dosages should be reduced in patients with liver dysfunction. On the other hand, theophylline is generally metabolized more rapidly in smokers (both tobacco and marijuana) and higher dosages may be required.

Beta-adrenergic bronchodilators

• Beta-adrenergic bronchodilators are used for treating children. However, there are no adequate studies of beta-adrenergic bronchodilator use during pregnancy. Some reports indicate that albuterol sulfate may cause congenital defects when used during pregnancy.
• It's not known whether beta-adrenergic bronchodilators are excreted in breast milk.

Anticholinergics

• The safety of anticholinergic bronchodilators in pregnant women or nursing mothers has not been adequately evaluated.

Xanthine bronchodilators

• Xanthine bronchodilators have not been adequately studied in pregnant women. Theophylline is excreted in breast milk and may cause mild side effects such as irritability in the infant.
• The risks to the fetus or breast-feeding infant versus the risk to the woman should be considered before using bronchodilators in pregnant women; consultation with the patient's OB/GYN doctor may be advisable.

Bronchodilators differ in their mechanism of action, how quickly they work, and their duration of action, their uses, side effects, and how they are administered.

• Beta-adrenergic bronchodilators are supplied as aerosols for inhalation, powders for inhalation, solution for nebulization, syrup, and tablets.
• Anticholinergic bronchodilators are supplied as solutions for inhalation, powder for inhalation, and nebulized solution.
• Xanthines are supplied as tablets, capsules, elixir, and solution for injection.

• Yes. Bronchodilators approved for treating asthma and other respiratory conditions are prescription products.
• Over the counter (OTC), homeopathic, or herbal products often promoted for treating asthma are not approved by the FDA and they are not considered effective by many doctors.