Bronchitol Side Effects: What to Expect and When to Call Your Doctor

If you've been prescribed Bronchitol (inhaled mannitol) for cystic fibrosis, understanding its potential side effects helps you know what to watch for and when something needs medical attention. Most side effects are manageable, but a few are serious enough to require stopping the medication immediately.

Common Side Effects of Bronchitol (3% or More of Patients)

In the three Phase 3 clinical trials that evaluated Bronchitol (totaling 761 adult CF patients), the following side effects occurred in 3% or more of patients receiving the 400 mg twice-daily dose:

Cough: The most frequently reported side effect. Coughing during or after inhaling Bronchitol is common and expected — it's actually part of how the medication works, by triggering productive coughing to clear mucus.

Hemoptysis (coughing up blood): Small streaks of blood in mucus are common in CF regardless of treatment. Bronchitol was associated with hemoptysis in some clinical trial participants. Important: coughing up a large amount of blood is a reason to stop Bronchitol immediately and contact your doctor.

Oropharyngeal pain: Soreness or irritation in the throat or mouth. Usually mild and may improve as your body adjusts to the medication.

Vomiting: Nausea and vomiting were reported in some patients. Taking your bronchodilator pre-medication 5–15 minutes before each dose may help reduce airway irritation that can trigger nausea.

Bacteria identified in sputum: This reflects the CF disease process rather than a direct drug effect — mucus clearing can reveal bacteria already present in the lungs.

Pyrexia (fever): Reported in some patients, often in the context of CF pulmonary exacerbations rather than a direct drug reaction.

Arthralgia (joint pain): Joint pain was reported in clinical trials, though its relationship to the medication versus underlying CF disease is not always clear.

Serious Side Effects — Stop Bronchitol and Call Your Doctor Immediately

Two serious adverse reactions require you to stop taking Bronchitol immediately and seek medical attention:

Severe bronchospasm: Bronchitol can cause sudden tightening of the airways (bronchospasm), even in patients who passed the Bronchitol Tolerance Test. Symptoms include sudden difficulty breathing, wheezing, severe chest tightness, or coughing that won't stop after inhalation. Use your rescue inhaler immediately and contact your CF care team or emergency services.

Significant hemoptysis: If you cough up a large amount of blood (ask your CF team what "large amount" means for your specific situation), stop taking Bronchitol immediately and contact your care team or go to the emergency room. Bronchitol should not be used in patients who have had significant hemoptysis (more than 60 mL) in the 3 months before starting therapy.

Pulmonary Exacerbations During Bronchitol Treatment

In clinical trials, CF pulmonary exacerbations (worsening of lung symptoms) occurred in about 32% of patients taking Bronchitol — similar to the 33% rate in the control group. This suggests Bronchitol doesn't significantly increase the risk of exacerbations overall, but it also doesn't eliminate them. Always contact your CF care team promptly if your breathing worsens, your mucus changes character, or you develop fever or feel generally unwell.

Tips for Managing Common Bronchitol Side Effects

For cough: Use your bronchodilator 5–15 minutes before every dose as prescribed. The coughing often becomes more productive over time as mucus clears.

For oropharyngeal pain: Rinsing your mouth with water after each dose may help reduce irritation. Alert your CF team if it becomes severe.

For nausea/vomiting: Try taking Bronchitol at a time when your stomach is not too full or too empty. If it persists, discuss timing adjustments with your care team.

For all side effects: Tell your CF care team at every visit. They can help determine whether the side effect is from Bronchitol or from the underlying CF disease.

Contraindications: When Not to Take Bronchitol

Bronchitol should not be used if:

You are allergic to mannitol or any component of the Bronchitol capsule

You failed the Bronchitol Tolerance Test

You have had significant hemoptysis (more than 60 mL) in the 3 months before starting therapy

You are under 18 years of age (Bronchitol is not indicated for pediatric use)

Also see our guide on Bronchitol Drug Interactions: What to Avoid and What to Tell Your Doctor.

For a full overview of Bronchitol: What Is Bronchitol? Uses, Dosage, and What You Need to Know in 2026.