What You Need to Know About Budesonide/Formoterol Side Effects

Every medication comes with potential side effects, and Budesonide/Formoterol is no exception. The good news? Most people tolerate this inhaler well, and the most common side effects are mild. But it's important to know what to watch for — especially the signs that mean you should call your doctor right away.

This guide covers the full range of side effects reported with Budesonide/Formoterol (brand names Symbicort and Breyna), based on FDA labeling and clinical data. We'll break down what's common, what's serious, and what you can do about it.

What Is Budesonide/Formoterol?

Budesonide/Formoterol is a combination inhaler used to treat asthma (in adults and children 6+) and COPD (chronic obstructive pulmonary disease) in adults. It contains two active ingredients:

• Budesonide — an inhaled corticosteroid (ICS) that reduces inflammation in the airways
• Formoterol — a long-acting beta2-agonist (LABA) that relaxes and opens the airways

Together, they control symptoms and prevent flare-ups. Budesonide/Formoterol is taken as 2 puffs twice daily and is not a rescue inhaler. For more details, see our full guide: What Is Budesonide/Formoterol? Uses, Dosage, and What You Need to Know.

Common Side Effects

The following side effects are relatively common and usually mild. They often improve as your body adjusts to the medication over the first few weeks:

• Throat irritation or pain — One of the most frequently reported side effects. The medication can irritate your throat as you inhale it.
• Oral thrush (candidiasis) — White patches in your mouth or throat caused by a fungal infection. This happens because the corticosteroid (Budesonide) can suppress local immune defenses in your mouth.
• Headache — Reported in clinical trials by a notable percentage of users.
• Upper respiratory infections — Cold-like symptoms including stuffy or runny nose, sneezing, and sore throat.
• Nasopharyngitis — Inflammation of the nose and throat, similar to a common cold.
• Back pain — Reported in clinical studies, though the exact mechanism isn't fully understood.
• Stomach discomfort, nausea, or vomiting — Some patients experience mild GI symptoms.
• Hoarseness (dysphonia) — Your voice may become raspy or weak, especially if you don't rinse your mouth after each use.
• Muscle cramps or spasms — Related to the Formoterol component, which can affect muscle function.
• Tremor or nervousness — Formoterol can cause a mild shaky feeling, particularly in the hands.

How to Reduce Common Side Effects

Many of these side effects can be minimized with a few simple habits:

• Rinse your mouth with water after every use and spit it out — don't swallow. This is the single most effective way to prevent oral thrush and throat irritation.
• Use a spacer if your doctor recommends one. A spacer helps more medication reach your lungs and less settle in your mouth and throat.
• Practice proper inhaler technique. Ask your pharmacist or doctor to watch you use your inhaler to make sure you're doing it correctly.
• Stay hydrated. Drinking water throughout the day can help with throat dryness and irritation.

Serious Side Effects

Serious side effects are less common but require prompt medical attention. Call your doctor right away if you experience any of the following:

Paradoxical Bronchospasm

In rare cases, Budesonide/Formoterol can cause sudden worsening of breathing problems — the opposite of what it's supposed to do. If your breathing gets worse immediately after using the inhaler, stop using it and use your rescue inhaler. Call your doctor right away.

Cardiovascular Effects

Formoterol can affect your heart. Watch for:

• Fast or pounding heartbeat (tachycardia)
• Chest pain
• Irregular heartbeat (arrhythmia)
• Increased blood pressure

These effects are more likely at higher doses or in people with pre-existing heart conditions.

Low Potassium (Hypokalemia)

Both Formoterol and corticosteroids can lower potassium levels. Symptoms include:

• Leg cramps
• Muscle weakness
• Irregular heartbeat
• Constipation
• Numbness or tingling

High Blood Sugar (Hyperglycemia)

Budesonide can raise blood sugar levels. This is especially important for people with diabetes. Watch for increased thirst, frequent urination, and dry mouth.

Eye Problems

Long-term use of inhaled corticosteroids like Budesonide has been linked to:

• Glaucoma (increased eye pressure)
• Cataracts (clouding of the lens)
• Blurred vision

If you notice any vision changes, see your eye doctor promptly.

Immune Suppression and Infections

Budesonide suppresses local and systemic immune function. This means:

• You may be more vulnerable to infections, including chicken pox and measles
• Existing infections (like tuberculosis) could worsen
• Fungal, bacterial, or viral infections may take longer to resolve

Adrenal Suppression

Long-term use of corticosteroids can suppress your adrenal glands, which produce important hormones. Symptoms include unusual tiredness, weakness, dizziness, nausea, and vomiting. This is more likely if you're switching from oral corticosteroids to inhaled ones — your doctor should taper the oral dose gradually.

Bone Density Loss

Long-term inhaled corticosteroid use may decrease bone mineral density, increasing the risk of osteoporosis and fractures. This is more relevant for patients on higher doses over many years.

Severe Allergic Reactions

Though rare, some people may have a serious allergic reaction. Seek emergency medical help if you experience:

• Hives or rash
• Swelling of the face, throat, tongue, or lips
• Difficulty breathing unrelated to your asthma or COPD

Specific Populations: Who's at Higher Risk?

Children (Ages 6 and Older)

Budesonide/Formoterol is approved for children ages 6 and up, but parents should know that inhaled corticosteroids may slow growth. Studies show children using Budesonide may grow about 0.5 to 1 centimeter less per year during the first 1 to 2 years of treatment. Your child's doctor should monitor their height regularly.

Pregnant Women

Budesonide/Formoterol is Category C for pregnancy. However, uncontrolled asthma poses serious risks to both mother and baby — including premature birth and low birth weight. Most experts agree the benefits of continued asthma control typically outweigh the risks. Talk to your OB-GYN and pulmonologist.

Older Adults

Elderly patients may be more sensitive to cardiovascular side effects like fast heartbeat and blood pressure changes. They're also at higher risk for bone density loss with long-term corticosteroid use.

People With Diabetes

Since Budesonide can raise blood sugar, diabetic patients should monitor glucose levels more closely after starting this medication.

The Boxed Warning: What You Should Know

Budesonide/Formoterol carries an FDA boxed warning — the most serious type of drug warning. Here's the key point: Long-acting beta2-agonists (LABAs) like Formoterol, when used alone, increase the risk of asthma-related death. However, clinical studies have shown that this risk is not increased when Formoterol is used in combination with an inhaled corticosteroid like Budesonide. That's exactly what Budesonide/Formoterol is — a combination product. So while the warning sounds alarming, using Budesonide/Formoterol as prescribed (with both ingredients together) is considered safe and effective.

When to Call Your Doctor

Contact your doctor if you experience:

• Side effects that don't go away or get worse over time
• Signs of oral thrush that don't clear up
• Increased need for your rescue inhaler
• Symptoms of low potassium, high blood sugar, or adrenal problems
• Any vision changes

Seek emergency medical help if you have:

• Sudden worsening of breathing after using the inhaler
• Chest pain or very fast/irregular heartbeat
• Signs of severe allergic reaction (swelling of face/throat, hives, difficulty breathing)

Final Thoughts

Budesonide/Formoterol is a well-established, effective medication for managing asthma and COPD. Most side effects are mild and manageable — especially when you practice good inhaler technique and rinse your mouth after each use. The serious side effects, while important to know about, are uncommon when the medication is used as directed.

If you're having trouble finding Budesonide/Formoterol at your pharmacy, Medfinder can help you locate it in stock near you. And for tips on reducing your costs, check out our savings guide.

For a deeper understanding of how this medication works in your body, read our guide: How Does Budesonide/Formoterol Work? Mechanism of Action Explained.