Vardenafil and Rifaximin: Can You Take Them Together?

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Vardenafil and Rifaximin: Understanding the Interaction

Published: 3 November 2026

Many men wonder whether vardenafil and rifaximin can be taken together safely. The good news is that no major interaction between these two medicines is commonly reported, but your prescriber will still review your full medication list during consultation to ensure the combination is appropriate for you. Vardenafil is a prescription treatment for erectile dysfunction, while rifaximin is an antibiotic used mainly for traveller's diarrhoea and certain bowel conditions.

What Is Vardenafil and How Does It Work?

Vardenafil (also known by the brand name Levitra) is a phosphodiesterase type 5 (PDE5) inhibitor licensed in the UK to treat erectile dysfunction [5]. It works by relaxing the blood vessels in the penis, allowing increased blood flow when you are sexually aroused. Vardenafil does not cause an erection on its own—sexual stimulation is still needed.

The medicine is available in 5mg, 10mg, and 20mg tablets, and is usually taken about 25 to 60 minutes before sexual activity [5]. The effect can last for several hours, but you should not take more than one dose in 24 hours. Like all PDE5 inhibitors, vardenafil is only available on prescription in the UK after a clinical assessment by a registered prescriber.

Common side effects include headache, flushing, nasal congestion, and indigestion. Vardenafil is not suitable for everyone—particularly those taking nitrates, nicorandil, riociguat, or another PDE5 inhibitor, as these combinations can cause a dangerous drop in blood pressure [5].

What Is Rifaximin and What Is It Used For?

Rifaximin is a prescription antibiotic that works mainly in the gut. Unlike many antibiotics, very little rifaximin is absorbed into the bloodstream, which means it acts locally in the bowel [12]. In the UK, rifaximin is most commonly prescribed for traveller's diarrhoea caused by certain bacteria, and for reducing episodes of hepatic encephalopathy (a complication of liver disease).

Because rifaximin stays largely in the digestive system, it has a different side-effect profile and interaction pattern compared to antibiotics that circulate widely in the body. Common side effects can include headache, dizziness, nausea, and abdominal pain, though many people tolerate it well.

Rifaximin is taken as tablets, usually two or three times a day depending on the condition being treated. The course length varies—traveller's diarrhoea is often treated for three days, while hepatic encephalopathy may require longer-term use. Always complete the course as prescribed, even if symptoms improve.

How Rifaximin Differs from Other Antibiotics

Rifaximin belongs to the rifamycin family of antibiotics, which includes rifampicin. However, rifaximin's minimal absorption into the bloodstream sets it apart. Rifampicin is a potent enzyme inducer that can reduce the effectiveness of many medicines, including vardenafil, by speeding up their breakdown in the liver. Rifaximin does not share this property to any clinically significant degree because so little enters the circulation [12].

Do Vardenafil and Rifaximin Interact with Each Other?

No major interaction between vardenafil and rifaximin is commonly reported in clinical practice or major drug-interaction databases. This is because rifaximin is poorly absorbed from the gut and does not significantly affect the liver enzymes (such as CYP3A4) that break down vardenafil [5][12]. In contrast, rifampicin—a related antibiotic that is well absorbed—can reduce vardenafil levels and make it less effective.

That said, every patient is different, and your prescriber will review all your current medicines, health conditions, and symptoms during your consultation. Even when no major interaction is expected, it is essential to declare every medicine you take, including over-the-counter products, herbal remedies, and supplements.

If you are prescribed rifaximin for a short course (such as for traveller's diarrhoea), your prescriber may advise continuing vardenafil as usual, provided there are no other concerns. For longer-term rifaximin use, ongoing monitoring ensures the combination remains safe and effective for you.

What Your Prescriber Will Check Before Approving Vardenafil

When you request vardenafil through Cured Pharmacy's online consultation, a UK-registered prescriber reviews your medical history and current medicines to ensure the treatment is safe for you. They will check for contraindications such as nitrate medicines (GTN spray, isosorbide mononitrate or dinitrate), nicorandil, riociguat, or recreational drugs known as 'poppers' (amyl or alkyl nitrites). Taking vardenafil with any of these can cause a dangerous fall in blood pressure—do not take them together [5].

The prescriber will also look for medicines that can interact with vardenafil. Alpha-blockers (such as doxazosin or tamsulosin, used for prostate symptoms or high blood pressure) can add to the blood-pressure-lowering effect, so you should be stable on the alpha-blocker and start vardenafil at the lowest dose [5]. Potent CYP3A4 inhibitors—including ritonavir, cobicistat, ketoconazole, itraconazole, and clarithromycin—can raise vardenafil levels significantly; vardenafil is often avoided or contraindicated with these medicines, so your prescriber must check the summary of product characteristics [5][12].

You will also be asked about heart conditions, recent stroke or heart attack, very low blood pressure, previous sudden vision loss (NAION), and inherited retinal disorders, as vardenafil may not be suitable in these situations [5]. Declaring rifaximin and any other medicines ensures a complete safety review.

Medicines That Must Never Be Taken with Vardenafil

Do not take vardenafil if you use nitrates (GTN spray, isosorbide mononitrate, isosorbide dinitrate), nicorandil, riociguat, poppers (amyl/alkyl nitrites), or another PDE5 inhibitor (sildenafil, tadalafil, avanafil). Combining these with vardenafil can cause a severe and potentially life-threatening drop in blood pressure [5]. If you are unsure whether any of your medicines fall into these categories, ask your GP or pharmacist before starting treatment.

Practical Advice: Taking Vardenafil and Rifaximin Together

If your prescriber approves the combination of vardenafil and rifaximin, you can usually take them on the same day without special timing requirements. Rifaximin is typically taken with or without food, according to your prescription instructions, while vardenafil can also be taken with or without food—though a very heavy or fatty meal may delay its effect [5][12].

Take vardenafil about 25 to 60 minutes before you plan to have sex, and remember that sexual stimulation is needed for it to work [5]. Do not take more than one dose of vardenafil in 24 hours. Continue your rifaximin course exactly as prescribed, even if your symptoms improve, to ensure the infection is fully treated.

Avoid drinking large amounts of alcohol while taking vardenafil, as alcohol can worsen erectile dysfunction and add to the blood-pressure-lowering effect, increasing the risk of dizziness or fainting. Grapefruit juice can raise vardenafil levels and should be avoided. If you experience dizziness, headache, or flushing, these are common side effects that often settle; however, if they are severe or persistent, contact your prescriber or pharmacist for advice.

What to Do If You Miss a Dose

Vardenafil is taken as needed before sexual activity, so there is no regular dosing schedule to miss. If you forget to take rifaximin at the scheduled time, take it as soon as you remember unless it is nearly time for your next dose—in that case, skip the missed dose and continue as normal. Never double up to make up for a forgotten dose. If you are unsure, check the patient information leaflet or ask your pharmacist.

Warning Signs and When to Seek Urgent Help

Most men tolerate vardenafil well, but you should be aware of warning signs that need urgent medical attention. If you develop an erection that lasts longer than four hours (priapism), go to A&E immediately or call 999—this is a medical emergency that requires prompt treatment to prevent permanent damage [5].

Sudden loss of vision in one or both eyes, or sudden decrease or loss of hearing (sometimes with ringing in the ears or dizziness), are rare but serious side effects. Stop taking vardenafil and seek urgent medical help if these occur [5]. If you experience chest pain during or after sex, do not use nitrate medicines to relieve it—tell the healthcare professional that you have taken vardenafil, as nitrates are contraindicated.

Severe allergic reactions (such as swelling of the face, lips, tongue, or throat, or difficulty breathing) are rare but require immediate emergency help. If you develop severe dizziness, fainting, or an irregular heartbeat, contact your GP urgently or call 111 for advice. For any concerns about rifaximin—such as severe diarrhoea, blood in stools, or signs of liver problems (yellowing of skin or eyes, dark urine)—contact your prescriber promptly.

Scientific References

1. Joint Formulary Committee. (n.d.). Vardenafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/vardenafil/ [accessed 3 November 2026]
2. Electronic Medicines Compendium. (n.d.). Summaries of Product Characteristics and Patient Information Leaflets. https://www.medicines.org.uk/emc/ [accessed 3 November 2026]
3. NHS. (n.d.). Erectile dysfunction (impotence). https://www.nhs.uk/conditions/erection-problems-erectile-dysfunction/ Accessed 3 November 2026.

Information on this page is for educational purposes only and is not medical advice. Prescription treatments require clinical assessment by a UK-registered prescriber. Always consult a qualified healthcare professional before starting or changing any medication.

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