Why Drug Interactions Matter with Dulera

Dulera (mometasone furoate/formoterol fumarate) contains two active ingredients, which means it has two sets of potential drug interactions. Some interactions are serious enough to cause dangerous side effects, while others may simply reduce how well Dulera works.

This guide covers the most important Dulera drug interactions, what to avoid, and what to tell your doctor before starting treatment. If you're new to this medication, start with What Is Dulera? for a complete overview.

Major Drug Interactions

These interactions can cause serious problems and should always be discussed with your doctor:

Beta-Blockers

Beta-blockers are medications used for high blood pressure, heart conditions, migraines, and anxiety. Common examples include metoprolol (Lopressor), atenolol (Tenormin), propranolol (Inderal), and carvedilol (Coreg).

The problem: Beta-blockers can block the bronchodilating effect of formoterol (the LABA in Dulera) and may cause severe bronchospasm — a dangerous tightening of the airways. This is especially true for non-selective beta-blockers like propranolol.

What to do: Tell your doctor about any beta-blocker you take. In some cases, a cardioselective beta-blocker (like metoprolol) may be used cautiously, but this decision must be made by your doctor. Never start or stop a beta-blocker without medical guidance.

Strong CYP3A4 Inhibitors

Mometasone (the corticosteroid in Dulera) is broken down in the body by an enzyme called CYP3A4. Drugs that block this enzyme cause mometasone to build up in your system, increasing the risk of corticosteroid side effects.

Strong CYP3A4 inhibitors include:

• Antifungals: Ketoconazole, itraconazole
• HIV medications: Ritonavir, cobicistat, atazanavir, indinavir, nelfinavir, saquinavir
• Antibiotics: Clarithromycin, telithromycin
• Other: Nefazodone (an antidepressant)

The problem: Increased systemic corticosteroid exposure can lead to adrenal suppression, Cushing's syndrome symptoms (weight gain, moon face, high blood sugar), bone density loss, and other steroid side effects.

What to do: If you need one of these medications, your doctor may choose a different asthma treatment or monitor you more closely. Do not start any of these drugs without telling your prescriber you're on Dulera.

MAO Inhibitors and Tricyclic Antidepressants

Monoamine oxidase (MAO) inhibitors and tricyclic antidepressants (TCAs) can amplify the cardiovascular effects of formoterol.

MAO inhibitors include: Phenelzine (Nardil), tranylcypromine (Parnate), selegiline (Emsam), isocarboxazid (Marplan)

Tricyclic antidepressants include: Amitriptyline, nortriptyline, desipramine, imipramine

The problem: These drugs can potentiate (strengthen) the cardiovascular effects of formoterol, including increased heart rate, elevated blood pressure, and heart rhythm changes. This combination can be dangerous, especially for people with existing heart conditions.

What to do: Tell your doctor if you take any antidepressant, including older ones. They may need to adjust your treatment plan or monitor your heart more closely.

Non-Potassium-Sparing Diuretics

Diuretics (water pills) that cause potassium loss — such as furosemide (Lasix), hydrochlorothiazide (HCTZ), and bumetanide — can interact with Dulera.

The problem: Formoterol can also lower potassium levels. Combined with a potassium-depleting diuretic, this may cause hypokalemia (dangerously low potassium), which can lead to muscle weakness, cramps, and heart rhythm problems.

What to do: Your doctor may monitor your potassium levels if you take both medications. Don't stop your diuretic without medical advice.

Moderate Drug Interactions

These interactions are worth knowing about and discussing with your doctor:

Other Long-Acting Beta2-Agonists

Do not use Dulera with another LABA (such as salmeterol or vilanterol in another inhaler). Using two LABAs together increases the risk of serious cardiovascular side effects without providing additional benefit.

Theophylline and Xanthine Derivatives

Theophylline is an older asthma medication still used in some cases. When combined with formoterol, it may have additive effects — increasing the risk of side effects like rapid heart rate, tremor, and low potassium.

QTc-Prolonging Medications

Formoterol can mildly prolong the QTc interval (a measurement of heart electrical activity). Other medications that also prolong QTc — such as certain antibiotics (azithromycin, fluoroquinolones), antipsychotics, and anti-arrhythmic drugs — may increase this risk when combined with Dulera.

Your doctor should review your full medication list for QTc-prolonging drugs before prescribing Dulera.

Food and Drink Interactions

Dulera has no known food or drink interactions. You can take it regardless of meals. There's no need to avoid any specific foods while using this inhaler.

What to Tell Your Doctor Before Starting Dulera

Before your doctor prescribes Dulera, make sure they know about:

• All prescription medications you take — including inhalers, pills, patches, and injections
• Over-the-counter medications — including cold medicines, pain relievers, and supplements
• Herbal supplements — Some, like St. John's Wort, can affect drug metabolism
• Any other inhalers — Especially if you use another LABA or corticosteroid inhaler
• Medical conditions — Especially heart disease, high blood pressure, seizures, diabetes, thyroid disorders, liver problems, and osteoporosis

If you're prescribed a new medication while already taking Dulera, remind that prescriber about your inhaler. Not all doctors check for inhaler interactions automatically.

Common Scenarios and What to Do

"I was just prescribed an antibiotic. Is it safe with Dulera?"

Most antibiotics are fine with Dulera. The exceptions are clarithromycin and telithromycin (strong CYP3A4 inhibitors). If you're prescribed one of these, tell your doctor you take Dulera.

"I take blood pressure medication. Should I be worried?"

It depends on the type. Beta-blockers are the main concern. ACE inhibitors, ARBs, and calcium channel blockers are generally safe with Dulera. If you take a diuretic, your doctor may want to monitor potassium levels.

"I use albuterol as my rescue inhaler. Can I still use it with Dulera?"

Yes. Albuterol is a short-acting beta2-agonist (SABA) and is safe to use alongside Dulera for acute asthma symptoms. Just don't use another long-acting beta2-agonist with Dulera.

"I take an antidepressant. Is that a problem?"

Modern antidepressants like SSRIs (sertraline, fluoxetine, escitalopram) and SNRIs (venlafaxine, duloxetine) are generally not a significant interaction concern with Dulera. The main caution is with older MAO inhibitors and tricyclic antidepressants. Check with your doctor to be sure.

How to Stay Safe

1. Keep an updated medication list — Include doses, and bring it to every doctor and pharmacy visit.
2. Use one pharmacy — Your pharmacist can automatically check for interactions across all your prescriptions.
3. Don't start or stop medications without checking — Even OTC drugs can sometimes interact.
4. Ask questions — If a new medication is prescribed, ask both your doctor and pharmacist if it's safe with Dulera.
5. Report new symptoms — If you experience rapid heartbeat, tremors, unusual weakness, or new side effects after starting a new medication, contact your doctor. For more on what to watch for, read about Dulera side effects.

The Bottom Line

Dulera is generally safe when used as prescribed, but its two active ingredients mean there are meaningful drug interactions to be aware of. Beta-blockers, strong CYP3A4 inhibitors, MAO inhibitors, and potassium-depleting diuretics are the biggest concerns. Keep your doctors informed, use one pharmacy, and don't hesitate to ask questions.

Need to fill your Dulera prescription? MedFinder helps you find Dulera in stock at pharmacies near you.