Bronchodilators: Nursing pharmacology

Bronchodilators are a group of medications that help breathing by keeping the airways dilated. That being said, they are typically used in obstructive lung diseases, like asthma and chronic obstructive pulmonary disease, or COPD for short, where clients suffer from narrowing and obstruction of the airways.

Asthma is characterized by chronic inflammation in the lungs, as well as asthma exacerbations or attacks, where certain triggers, such as viruses, allergens, stress, aspirin or other NSAIDs and exercise, lead to reversible bronchial smooth muscle spasms and mucus production, both of which make it hard to breathe.

As a result, clients experience symptoms like dyspnea, wheezing, chest tightness, and coughing. On the other hand, in COPD, there’s chronic inflammation and fibrosis in the lungs, most commonly due to smoking.

As a result, the airways become irreversibly obstructed and the lungs are not able to empty properly, which leaves air trapped inside the lungs.

As a result, clients experience symptoms like dyspnea and a productive cough. Now, COPD generally refers to a group of progressive lung diseases that includes chronic bronchitis and emphysema.

These two differ in that chronic bronchitis is defined by long-term inflammation of the bronchial tubes, whereas emphysema is defined by destruction and enlargement of the alveoli.

Although the airway obstruction in COPD is irreversible, bronchodilators can often help prevent the complete closure of the airway during expiration, which provides mild symptomatic relief.

Now, based on their mechanism of action, bronchodilators can be broadly divided into three main groups; β2-agonists; anticholinergics; and methylxanthines.

The effect of all these medications is bronchial smooth muscle relaxation, which in turn results in dilation of the narrowed airways and improved air flow.

In particular, β2-agonists, like albuterol and salmeterol, come in an aerosolized form, and can be taken via metered dose inhalers or MDIs, or nebulizers.

Once in the lungs, they bind to and activate the β2 adrenergic receptors on bronchial smooth muscle cells, ultimately promoting relaxation of the smooth muscle.

β-2 agonists can be classified, based on the duration of action, into short acting β-2 agonists, or SABAs, such as albuterol, and long acting β-2 agonists, or LABAs, like salmeterol.

SABAs are typically the treatment of choice for quick symptom relief in acute asthmatic attacks, whereas LABAs are often used in combination with an inhaled corticosteroid like budesonide as prophylactic or maintenance treatment for asthma and COPD.

On the other hand, commonly used anticholinergics include ipratropium and tiotropium, and can also be given via inhalers or nebulizers.

Once in the airways, they bind to M3 muscarinic receptors on the tracheal and bronchial smooth muscles. This blocks acetylcholine from binding to the receptors, decreasing smooth muscle constriction.

In comparison to β2-agonists, anticholinergics are less effective for asthma, but more effective for COPD, where they are the bronchodilators of choice.

However, for severe cases of asthma or COPD, anticholinergics are often given in combination with LABAs for an additive effect, leading to stronger and longer lasting bronchodilation.

Finally, methylxanthines, such as theophylline, are usually taken orally, but can also be administered intravenously. Once methylxanthines reach the airways, they inhibit the enzyme phosphodiesterase, or PDE, and ultimately lead to smooth muscle relaxation.

These medications can be used in asthma and COPD. Okay, now each group of bronchodilators has its own set of side effects.

With β-2 agonists, the most common ones are muscle tremors, restlessness, and insomnia, as well as tachycardia, and palpitations.

Some clients may even develop arrhythmias, especially with LABAs, which could result in heart failure or even death. As a result, β-2 agonists should be used with caution in clients with concurrent heart or renal disease, hyperthyroidism, diabetes mellitus, and pregnancy.

Moving on to anticholinergics, common side effects include pupil dilation, dry mouth, tachycardia, and restlessness. For that reason, anticholinergics should be used with caution in clients with narrow angle glaucoma, heart disease, and hyperthyroidism, and are contraindicated in clients with a previous hypersensitivity or allergic reaction.

Finally, the methylxanthine theophylline may result in side effects like insomnia, nausea, and vomiting. In addition, theophylline has a very narrow therapeutic window, meaning it's very easy to overdose, and can cause seizures and arrhythmias.

Now, theophylline should be avoided in clients with seizure disorders, heart, renal or liver disease. Drug interactions with beta blockers, phenytoin, beta adrenergic agonists, antidepressants, or certain antibiotics like ciprofloxacin can also lead to synergistic effects and cardiac dysrhythmias.

Due to the dangerous potential side effects, theophylline is now rarely used. Now, before administering bronchodilators, ensure the client understands why the medication is prescribed, the correct method of administration, and side effects that may be experienced while taking the medication.

Then, assess your client’s respiratory status, baseline vital signs and lung sounds. If you’re administering theophylline, assess your client for signs of theophylline toxicity, and be sure to confirm the serum theophylline level, because toxicity can occur at levels greater than 20 mcg/mL, which is very close to the therapeutic dose.

Next, teach your client how to administer their medication. When using an MDI, demonstrate how to use a spacer, and explain that it promotes maximal delivery of the medication to the lungs.

Demonstrate how to shake the MDI canister and attach the spacer; then show them how to exhale all the air out of their lungs, put the spacer mouthpiece in their mouth, making a tight seal; and then press down on the MDI.

At this point, explain that the medication is now trapped in the spacer; so next they should inhale slowly and deeply, hold their breath for 5-10 seconds; and then fully exhale.

If the client needs to take more than one puff of the inhaled corticosteroid at one time, instruct them to wait one minute before administering the second puff.

After the demonstration, ask your client to provide a return demonstration so you’re sure they feel comfortable self-administering their medication.

Finally, be sure to educate your client to rinse out their mouth after inhalation since any medication that’s left behind in the oral cavity can lead to oral infections, such as thrush.

If administering theophylline IV, always use an infusion pump and administer it slowly. When administering theophylline orally, remember to never crush the enteric coated or sustained release tablets.

Instruct your client to avoid smoking, caffeine and alcohol use when taking theophylline as these can increase the side effects.

After administration of a bronchodilator, assess the client’s lung sounds and vital signs. Notify the health care provider if there are significant changes from the baseline or if the client experiences any bronchospasms, cardiac dysrhythmias or seizures.

Finally, evaluate for the desired therapeutic effects of decreased dyspnea, improved wheezing, and improved airway exchange.

Alright, as a quick recap… Bronchodilators are a group of medications that help breathing by keeping the airways dilated through smooth muscle relaxation, dilation of the narrowed airways, and improved air flow.

Bronchodilators can be broadly divided into three main groups; β2-agonists; anticholinergics; and methylxanthines. They are typically used in obstructive lung diseases, like asthma and COPD.

Before administering bronchodilators, be sure to assess baseline vital signs and lung sounds. Bronchodilators come in various forms but are commonly administered as inhaled medication.

After administration, assess for the desired therapeutic effects of decreased dyspnea, improved wheezing, and improved airway exchange.