7 Erectile Dysfunction (ED) Medication Interactions — Plus Bonus Interactions to Consider

Erectile dysfunction (ED) medications are safe and effective overall. But starting a new treatment may naturally bring safety concerns to mind — especially whether it interacts with a medication, supplement, or food you’re already taking.

Viagra (sildenafil) is an example of a popular ED medication. If you just received a prescription for it, you may have questions. Can you take Viagra with blood thinners? Can you take Eliquis and Viagra together? What else can’t you take with Viagra?

Concerns like these are understandable. Rest assured, your prescriber and pharmacist can help ease your mind by screening for potential interactions before you start an ED medication.

Below, we’ll break down seven ED interactions and how to manage them.

1. Nitrates

If you’re living with coronary artery disease, you may have a nitrate prescription to relieve chest pain. Nitrostat (nitroglycerin) and Monoket (isosorbide mononitrate) are a couple of nitrate examples. They relax blood vessels, which can also lower blood pressure.

ED medications called phosphodiesterase 5 (PDE5) inhibitors also work by relaxing blood vessels. They bring more blood flow to the penis for an erection. But, like nitrates, PDE5 inhibitors can lower blood pressure. This effect can be additive and dangerous. These PDE5 inhibitors interact with nitrates:

• Viagra

• Cialis (tadalafil)

• Stendra (avanafil)

• Vardenafil

If your blood pressure drops too low, you may experience symptoms such as dizziness and fainting. Taking nitrates and PDE5 inhibitors together could also raise the risk of heart complications. The combination is life-threatening and should be avoided.

By comparison, Caverject and Edex are prostaglandin injections that manage ED — they’re not PDE5 inhibitors. They both contain the active ingredient alprostadil. One feature is they have fewer interactions than PDE5 inhibitors, including with nitrates. It’s a similar story for TriMix injections (alprostadil / phentolamine / papaverine). These products are injected directly into the penis, so your body doesn’t absorb as much of the medication.

Good to know: The American Heart Association provides guidance on how long to separate PDE5 inhibitors from nitrates. Wait at least 24 hours after taking Viagra, Stendra, or vardenafil to take a nitrate. Cialis remains in the body longer than other PDE5 inhibitors, so wait at least 48 hours (2 days) to take a nitrate after using Cialis.

2. Alpha blockers

Alpha blockers treat a variety of health conditions, such as an enlarged prostate and hypertension (high blood pressure). Flomax (tamsulosin), Cardura (doxazosin), and Uroxatral (alfuzosin) are three common ones.

Like nitrates, alpha blockers work by widening blood vessels. Taking an alpha blocker with PDE5 inhibitors like Cialis can cause low blood pressure.

EXPERT PICKS: WHAT TO READ NEXT

• Pharmacist tips: From when to take Viagra (sildenafil) to how long it lasts, hear from experts about how to maximize this erectile dysfunction prescription.

• Taking Cialis: Your Cialis (tadalafil) dosage may vary depending on whether you take it daily or as needed. Learn more about how to take Cialis.

• Viagra side effects: Viagra typically causes mild side effects, such as headache and flushing (skin reddening). Here’s a list of common Viagra side effects and how to manage them.

You don’t have to avoid the combination altogether, but a healthcare professional will likely want your body to get used to the alpha blocker before starting a PDE5 inhibitor. Your ED medication starting dose may also be lower to prevent side effects.

Check out the table below for PDE5 inhibitor starting doses if you’re taking an alpha blocker.

Caverject and Edex don’t directly interact with alpha blockers. But the combination could still lower your blood pressure. Your prescriber can tell if your medication doses should be adjusted at all in this case.

Regardless of the specific combination, it’s a good idea to routinely check your blood pressure at home. If it’s less than 90/60 mmHg, tell a healthcare professional. Dizziness, confusion, and weakness are related symptoms that signal it’s time to seek medical attention.

3. Blood pressure medications

If you have hypertension, one or more blood pressure medications are likely part of your daily routine. But they can interact with PDE5 inhibitors. Combining them could lower your blood pressure too much.

Several groups of blood pressure medications may interact with your ED medication, including:

• Calcium channel blockers, such as Norvasc (amlodipine)

• Angiotensin-converting enzyme (ACE) inhibitors, such as Zestril (lisinopril)

• Angiotensin II receptor blockers, such as Cozaar (losartan)

• Thiazide diuretics (“water pills”), such as Microzide (hydrochlorothiazide)

• Beta blockers, such as Lopressor (metoprolol)

You likely won’t need to avoid these combinations altogether. But monitoring your blood pressure at home is a good way to stay on top of any episodes of low blood pressure.

Good to know: Blood pressure medications can also worsen ED symptoms. Beta blockers and thiazide diuretics are the top culprits. If you’re having trouble achieving an erection, tell your prescriber. They may switch you to a different blood pressure medication, such as an ACE inhibitor, that’s less likely to cause ED.

4. Blood thinners

Blood thinners are life-saving medications that treat and prevent blood clots. Coumadin (warfarin), Eliquis (apixaban), and Xarelto (rivaroxaban) are three of many.

PDE5 inhibitors and blood thinners

Ask a pharmacist: Can you take Viagra with blood thinners? They will likely say yes — with caution.

Research shows PDE5 inhibitors may slightly raise your chances of bleeding. But it’s likely not a significant risk, even if you’re taking a blood thinner. For instance, available data suggests warfarin and sildenafil are generally OK to take together.

Another study looked at potential interactions between PDE5 inhibitors and blood thinners called direct-acting oral anticoagulants — namely, Eliquis and Xarelto. The lab study found that PDE5 inhibitors raised the concentration of these blood thinners, but the clinical relevance wasn’t clear.

A healthcare professional will make the final decision on whether it’s OK to take these medications in combination with one another. But if you experience any signs or symptoms of bleeding while taking blood thinners and ED medications — such as nosebleeds, bleeding gums, or bloody stools — tell a healthcare professional immediately.

Alprostadil and blood thinners

Bleeding risks are a little different with alprostadil. Since Caverject and Edex are injections, you may experience more bleeding than normal at the injection site if you’re taking a blood thinner.

After you administer these medications, it’s best to press down on the injection site with a sterile gauze pad or an alcohol swab for about 5 minutes to prevent any bleeding.

5. St. John’s wort

St. John’s wort is a dietary supplement that’s marketed for depression symptoms. But it interacts with a variety of medications, including PDE5 inhibitors.

St. John’s wort induces certain liver enzymes. This means the enzymes are prompted to break down (metabolize) affected medications faster than normal. This could make Viagra less effective for treating ED. Cialis, Stendra, and vardenafil interact with St. John’s wort in the same way.

If you’re taking St. John’s wort and a PDE5 inhibitor, tell a healthcare professional if your ED medication stops working. They may recommend stopping St. John’s wort and trying a prescription antidepressant instead.

6. Alcohol

Alcohol interacts with a variety of medications, including PDE5 inhibitors. The combination may lead to low blood pressure.

This risk is mostly relevant if you consume large amounts of alcohol. Having an occasional drink should be fine as long as a healthcare professional says it’s OK.

Keep in mind that alcohol consumption can exacerbate ED symptoms. Alcohol acts as a depressant. It can slow down brain signals that help with achieving an erection.

7. Grapefruit juice

Grapefruit juice tends to have the opposite effect as St. John’s wort. Grapefruit products block certain liver enzymes. This effect can cause PDE5 inhibitors, such as vardenafil, to build up in the body. Higher blood levels of these medications raise the risk of low blood pressure and other side effects. Viagra, Cialis, and Stendra have the same interaction.

To be safe, avoid grapefruit products. But if grapefruit juice is your go-to beverage, ask a healthcare professional to see how much is safe to have. Small amounts may be OK.

Other ED medication interactions to consider

In addition to what’s listed above, there are other ED medication interactions to consider. Here are more examples of medications that may interact with PDE5 inhibitors:

• Paxlovid (nirmatrelvir / ritonavir)

• Ery-Tab (erythromycin)

• Ketoconazole

• Sporanox (itraconazole)

• Adempas (riociguat)

• Verquvo (vericiguat)

• Tracleer (bosentan)

• Rifadin (rifampin)

• Tegretol (carbamazepine)

• Dilantin (phenytoin)

• Sandimmune (cyclosporine)

• Phenobarbital

• Tagamet HB (cimetidine)

• Clarithromycin

Why trust our experts?

Written by:

Jennifer Gershman, PharmD, CPh, PACS

Jennifer Gershman, PharmD, is a licensed pharmacist in Florida. She has worked in the pharmacy industry for more than 15 years and is currently a medical writer.

Edited by:

Joshua Murdock, PharmD, BCBBS

Joshua Murdock, PharmD, BCBBS, is a licensed pharmacist in Arizona, Colorado, and Rhode Island. He has worked in the pharmacy industry for more than 10 years and currently serves as a pharmacy editor for GoodRx.

Reviewed by:

Ferras Bashqoy, PharmD, BCCCP, BCPPS

Ferras Bashqoy, PharmD, BCCCP, BCPPS, is a clinical pharmacotherapy specialist in the Neonatal Intensive Care Unit (NICU) at Hassenfeld Children’s Hospital in New York City. His favorite part of the job is working with preterm newborns because they are strong and mighty despite their size.

Our editorial standards

Meet our experts