What is bronchitis in dogs?
Bronchitis is the inflammation of the bronchi and bronchioles in the lungs (Trudell, 2022). The bronchi and bronchioles are the airways that transport air into and out of the lungs. With bronchitis, the linings of these airways swell and produce excess mucus, which can make breathing difficult.
The main symptoms of bronchitis in dogs include (Merck Vet Manual, 2022):
- Coughing
- Wheezing
- Breathing difficulties
- Lack of energy
- Loss of appetite
Bronchitis can be caused by different factors like inhaled irritants, allergies, respiratory infections, heart disease, and inhaled foreign bodies. Both acute and chronic bronchitis occur in dogs. Acute bronchitis involves a sudden onset and lasts for a short time. Chronic bronchitis involves long-term inflammation and permanent changes to the airways.
Why bronchodilators are used
Bronchodilators are commonly used in dogs with bronchitis to open up the airways and make breathing easier. Bronchodilators work by relaxing the smooth muscles around the bronchial tubes, which can narrow and tighten during bronchospasms (1). This helps to dilate the bronchi and bronchioles, allowing more air to pass through (2). As a result, bronchodilators help relieve coughing, wheezing, shortness of breath, and other symptoms caused by constricted airways.
Some of the main effects of bronchodilators in dogs include:
- Widening the air passages and bronchial tubes
- Relaxing bronchial smooth muscle to relieve bronchospasms
- Reducing airway resistance to improve airflow and ventilation
- Increasing the amount of air that can be inhaled and exhaled
- Making breathing easier and relieving symptoms of bronchial constriction
By opening up constricted airways, bronchodilators help improve overall lung function and breathing in dogs with bronchitis (3). This provides symptom relief and makes it easier for the dog to breathe.
(1) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7055016/
(2) https://pubmed.ncbi.nlm.nih.gov/7864949/
(3) https://www.aafp.org/pubs/afp/issues/1998/1015/p1303a.html
Types of bronchodilators for dogs
There are several types of bronchodilators that can be used to treat bronchitis in dogs:
Short-acting bronchodilators work quickly to open up the airways by relaxing the muscles around the bronchial tubes (bronchodilation). However, the effects only last for 4-6 hours. Examples include:
- Albuterol (Ventolin®) – relaxes airway smooth muscle in the lungs, making it easier to breathe. It is administered via a metered dose inhaler device with a spacer for dogs. [1]
- Levalbuterol (Xopenex®) – the purified active isomer of albuterol that also provides short-term bronchodilation. It is nebulized for inhalation in dogs. [2]
Long-acting bronchodilators have a slower onset of action but the effects can last up to 12 hours. These include:
- Salmeterol (Serevent®) – lasts longer than short-acting bronchodilators and is used to prevent bronchospasm. It is delivered via an inhaler. [1]
- Formoterol (Foradil®, PerforomistTM) – relaxes bronchial smooth muscle for up to 12 hours. It comes as an inhalation powder or nebulizer solution. [2]
Anticholinergics like ipratropium (Atrovent®) block acetylcholine receptors which cause bronchial muscle constriction. Ipratropium also provides bronchodilation but has a slower onset than short-acting bronchodilators. It is administered via inhalation devices. [1]
[1] https://vcahospitals.com/know-your-pet/theophylline
[2] https://www.merckvetmanual.com/special-pet-topics/drugs-and-vaccines/drugs-used-to-treat-lung-and-airway-disorders
How bronchodilators help
Bronchodilators help dogs with bronchitis by relaxing the muscles around the airways (bronchi and bronchioles). This helps open up the airways and keeps them from tightening. Bronchodilators work by reducing smooth muscle constriction and relieving bronchospasm. This improves the flow of oxygen, allows air to move in and out of the lungs more easily, and reduces air trapping in the lungs.
Bronchodilators also help decrease inflammation in the airways. By opening up the airways, they help reduce swelling and mucus buildup. This makes breathing easier for dogs with bronchitis.
Some key ways bronchodilators help dogs with bronchitis:
- Relax airway muscles and open up constricted airways
- Improve oxygen flow to the lungs
- Reduce air trapping in the lungs
- Decrease inflammation and mucus production
By improving airflow and reducing swelling in the airways, bronchodilators make breathing easier for dogs with bronchitis and improve respiratory function.
Dosage and administration
The dosage of bronchodilators depends on the specific drug prescribed by your veterinarian. Short acting bronchodilators like albuterol are typically dosed every 6 to 8 hours as needed to control symptoms. Long acting bronchodilators like salmeterol are dosed every 12 hours. Theophylline is a oral bronchodilator given every 8 to 12 hours.
Bronchodilators can be administered via inhaler, nebulizer, or orally. Using an inhaler with a spacer adapted for dogs allows the medication to be inhaled directly into the lungs. Nebulizers convert liquid medication into a mist that is inhaled. Theophylline is available as an oral tablet. Your veterinarian will decide the best method of administration for your dog.
Follow your veterinarian’s dosing instructions carefully and do not adjust or stop medication without consulting your vet first. Careful monitoring is required to achieve good control of symptoms while avoiding side effects.
Side Effects
Some of the most common side effects of bronchodilators in dogs include:
- Tremors and restlessness – Bronchodilators like theophylline can cause tremors and restlessness in dogs due to their stimulant effects on the central nervous system (1). According to VCA Hospitals, excitement is a common side effect of theophylline (2).
- Rapid heart rate – Bronchodilators may also cause rapid or irregular heart rates (arrhythmias) in some dogs. According to Wedgewood Pharmacy, abnormal heart rhythms are a less common but serious side effect of theophylline (3).
- Cough/throat irritation – Bronchodilators like theophylline can irritate the throat and cause coughing in dogs.
- Upset stomach – Nausea, vomiting and diarrhea are common side effects of bronchodilators like theophylline, caused by irritation of the stomach and intestines (1, 2).
Precautions
Bronchodilators like albuterol should be used cautiously in dogs with heart conditions like arrhythmias or cardiomyopathy, as the medication can increase heart rate and blood pressure (1). It’s important to monitor dogs on albuterol for signs of worsening heart disease. Some dogs may also experience paradoxical bronchoconstriction, where their airways narrow instead of relax after taking a bronchodilator. If this occurs, discontinue albuterol and contact your veterinarian (2). When starting albuterol, it should not abruptly replace other medications the dog is taking for bronchitis. Work with your vet on slowly transitioning to albuterol to avoid complications (3). Monitor your dog closely when first using albuterol and report any concerning side effects to your veterinarian.
Interactions
Theophylline can interact with several types of medications that dogs may be taking. Here are some key interactions to be aware of:
Beta-blockers: Theophylline should not be administered along with beta-blockers like propranolol as this can lead to severe hypotension and bradycardia. The effects of beta-blockers are opposed by theophylline.1
Diuretics: Theophylline can decrease the diuretic effects of furosemide. Theophylline is also associated with hypokalemia, so potassium-depleting diuretics like furosemide should be used with caution.2
Digoxin: Theophylline can increase serum digoxin concentrations. Dosages may need to be adjusted and levels monitored when used together.3
MAO inhibitors: Theophylline metabolism can be significantly reduced when administered along with MAO inhibitors like selegiline. This increases the risk of theophylline toxicity.1
Tricyclic antidepressants: Similar to MAO inhibitors, tricyclic antidepressants like amitriptyline can reduce the metabolism of theophylline and increase potential for toxicity.2
Lifestyle adjustments
There are several lifestyle adjustments you can make to help avoid triggers and irritants that could exacerbate your dog’s bronchitis symptoms:
Avoid triggers/irritants: Steer clear of dust, smoke, pollen or other potential allergens that could irritate your dog’s respiratory system. Try to keep your home clean and dust-free, and avoid using harsh chemical cleaners or air fresheners.
Use air filters/humidifiers: Use high efficiency particulate air (HEPA) filters or humidifiers to help remove allergens and pollutants from the air and add moisture. Proper humidity levels can help soothe irritated airways.
Don’t smoke around dog: Avoid smoking around your dog, as secondhand smoke is an irritant that can worsen bronchitis symptoms. Take smoking outside if possible.
In addition, regular moderate exercise can help strengthen your dog’s respiratory system over time. But avoid overexertion during acute flare ups of bronchitis. Follow your vet’s guidance on safe activity levels.
When to See a Vet
If your dog’s breathing difficulties are not improving even after starting bronchodilators, it’s important to follow up with your vet. Side effects like restlessness, vomiting, diarrhea or seizures can also occur with some bronchodilators, and warrant an urgent vet visit. If your dog experiences worsening cough or wheezing, or has breathing difficulties even at rest, promptly contact your vet for an evaluation. They may adjust medications or provide additional treatments like oxygen therapy if your dog is in respiratory distress.
According to the Blue Pearl Veterinary Partners article Canine Chronic Bronchitis, “If clinical signs do not improve or worsen despite appropriate therapy, further diagnostics such as bronchoscopy or computed tomography (CT) may be warranted.” Your vet can determine if additional diagnostics are needed to identify an underlying cause or complication.
As per VCAAH, urgent vet care is required if your dog has pale gums, collapse or fainting. These can signal severely inadequate oxygen levels. Prompt care can prevent complications and save your dog’s life in such cases of respiratory crisis.
