9 Erythromycin Interactions: From Statins to Viagra

Erythromycin (Ery-Tab) is a macrolide antibiotic that was discovered in 1952, and it’s still prescribed for certain uses. You can find it in a variety of dosage forms, from an oral tablet, capsule, and solution to intravenous (IV) forms used in healthcare settings. Topical erythromycin forms are also available.

Erythromycin has many potential interactions — specifically if you take it by mouth or receive an IV infusion. Certain risky combinations should be avoided. Other combinations may be managed with dosage adjustments or a watchful eye. So, which oral and IV erythromycin interactions should you know about? We cover nine of them below.

1. Statins such as simvastatin

Statins are a class of medications used to treat high cholesterol. Some statins, such as simvastatin (Zocor) and lovastatin, can interact with erythromycin. Taking them with erythromycin can increase their levels in your body. This raises the risk of muscle pain and serious muscle damage that can result in kidney failure (rhabdomyolysis).

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If you’re already taking a statin, your healthcare provider may recommend an alternative antibiotic. There are often other medications that can treat the same conditions as erythromycin. Or, your provider may suggest pausing your statin treatment if you need to take erythromycin.

2. Viagra

Viagra (sildenafil) is commonly prescribed to treat erectile dysfunction. When it’s combined with erythromycin, Viagra can reach higher levels than normal in the body. For that reason, Viagra’s labeling recommends starting with a lower Viagra dose (25 mg) when it’s taken with erythromycin.

Higher levels of Viagra can increase your risk of side effects, such as headache, flushing, and dizziness. Be sure to tell your healthcare provider if you take Viagra. They can help you avoid problems from this interaction.

3. Colchicine

Colchicine (Colcrys, Mitigare) is a medication that treats and prevents gout flares. It’s also available under the brand name Lodoco to lower the risk of heart attack and stroke in certain people. When it’s combined with erythromycin, colchicine levels in the body can be higher than expected. This can increase the risk of side effects, such as diarrhea, nausea, and vomiting.

If you need to take these medications together, your healthcare provider will likely lower your colchicine dose to reduce the risk of side effects.

4. Benzodiazepines

Benzodiazepines (BZDs) are a class of medications used to treat many conditions, such as anxiety, insomnia, and seizures. When taken with certain BZDs, erythromycin can increase their levels in the body. This raises the risk of BZD side effects, including drowsiness, confusion, and slowed breathing.

Not all BZDs interact with erythromycin. Examples of those that can interact include triazolam (Halcion) and alprazolam (Xanax). Your healthcare provider can determine if this interaction affects you and, if so, how to manage it. This may include lowering your BZD dose.

5. Ergot alkaloids

Erogotamine (Ergomar) and dihydroergotamine (Migranal) are two ergot alkaloids used to treat migraines. As with other interactions covered so far, erythromycin increases the levels of these medications in your body. This combination can result in ergot toxicity, which can result in loss of blood flow to your extremities, heart, and other tissues.

Due to the risk of ergot toxicity, you should avoid this combination. Your healthcare provider and pharmacist can help you avoid this interaction.

6. Digoxin

Digoxin (Lanoxin) is a medication that’s prescribed to treat health conditions such as heart failure and atrial fibrillation. As it does with many other medications, erythromycin can increase levels of digoxin in your body. This raises the risk of digoxin side effects, such as stomach problems and vision changes.

Before you start erythromycin, your healthcare provider may check your digoxin levels. They may also lower your digoxin dose or change how often you take it. Let them know right away if you develop new or worsening side effects.

7. Verapamil

Verapamil is a calcium channel blocker that’s used to treat high blood pressure and chest pain. Combining erythromycin and verapamil has been shown to cause low blood pressure (hypotension), low heart rate (bradycardia), and a build-up of lactic acid in the body.

If you need to take erythromycin and verapamil, your healthcare provider may adjust your verapamil dosage. Otherwise, they may recommend a different antibiotic that doesn’t interact.

8. Theophylline

Theophylline is sometimes used to treat asthma and chronic obstructive pulmonary disease (COPD). Erythromycin can raise theophylline levels in the body. But, this may be more likely with higher theophylline doses. What’s more, theophylline may lower erythromycin levels in the body, making it less effective.

Your healthcare provider may suggest a different antibiotic that doesn’t interact with theophylline. But if you need to take theophylline and erythromycin together, they can determine how best to manage this interaction. This may include dosage adjustments and more frequent monitoring.

9. Blood thinners

Blood thinners, or anticoagulants, are used to treat and prevent blood clots. Examples include  warfarin and Eliquis (apixaban). Taking erythromycin with an anticoagulant may increase the risk of bleeding, especially for older adults.

Watch closely for signs of unusual bruising and bleeding with this combination. If you’re taking warfarin, your healthcare provider may check your blood work more often to manage this interaction.

When should you contact your healthcare provider about erythromycin interactions?

Anytime you’re concerned about erythromycin interactions, it’s a good idea to check with your healthcare provider. Your pharmacist is also a helpful resource for information about interactions.

Ideally, any questions about interactions should be cleared up before starting a new medication. It’s generally easier to prevent dangerous interactions than to manage them if they happen. That’s why it’s important to share your current medication list with your healthcare provider and pharmacist. This helps them screen for potential interactions ahead of time.

If you’re experiencing new or worsening side effects while taking erythromycin, they could be related to an interaction. Erythromycin tends to increase the side effects of other medications. So, there are many different symptoms you could experience.

When in doubt, it never hurts to double-check by contacting your healthcare provider. If you have symptoms that seem severe or life-threatening, get medical help right away by calling 911 or going to the nearest ER.

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Written by:

Austin Ulrich, PharmD, BCACP

Austin Ulrich, PharmD, BCACP, is a board-certified ambulatory care clinical pharmacist. In his early career, he provided direct patient care in a variety of settings, including hospital and community pharmacies, and in a primary care clinic as a clinical pharmacist.

Edited by:

Alyssa Billingsley, PharmD

Alyssa Billingsley, PharmD, is the director of pharmacy content for GoodRx. She has over a decade of experience as a pharmacist and has worked in clinical, academic, and administrative roles.

Reviewed by:

Christina Aungst, PharmD

Christina Aungst, PharmD, is a pharmacy editor for GoodRx. She began writing for GoodRx Health in 2019, transitioning from freelance writer to editor in 2021.

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