Vardenafil and Diltiazem: Can They Be Taken Together?
Learn how these medicines interact and what safety checks your prescriber will carry out.
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Vardenafil and Diltiazem: Understanding the Interaction
Published: 29 October 2026
Many men taking diltiazem for high blood pressure or angina wonder whether vardenafil and diltiazem can be used together safely. The good news is that these two medicines can often be prescribed together, but the combination requires careful assessment by your prescriber because both can lower blood pressure. This page explains what each medicine does, how they interact, what checks your doctor or pharmacist will carry out, and the practical steps you can take to use them safely.
Key takeaways
- Vardenafil and diltiazem can often be taken together, but a lower starting dose of vardenafil is usually needed.
- Both medicines lower blood pressure, so watch for dizziness or light-headedness when standing up.
- Diltiazem increases vardenafil levels, which is why your prescriber will start you on 5 mg vardenafil.
- Avoid grapefruit juice and heavy alcohol, and never take vardenafil with nitrates or nicorandil.
- Seek urgent help if you have chest pain, an erection lasting over four hours, or sudden vision or hearing loss.
What Is Vardenafil and How Does It Work?
Vardenafil is a prescription medicine used to treat erectile dysfunction (ED) in adult men. It is the generic version of Levitra and belongs to a group of medicines called PDE5 inhibitors [5]. Vardenafil works by relaxing the blood vessels in the penis, allowing more blood to flow into the area when you are sexually aroused. This helps you to get and keep an erection suitable for sexual activity [5].
Vardenafil is usually taken about 25 to 60 minutes before sex, and the effect can last for several hours [5]. It is available in 5 mg, 10 mg, and 20 mg tablets, and the usual starting dose is 10 mg. You should take it no more than once a day. Vardenafil will not work without sexual stimulation, and it does not increase sexual desire [5].
Like all PDE5 inhibitors, vardenafil can cause side effects such as headache, flushing, indigestion, and nasal congestion. It can also lower blood pressure slightly, which is why interactions with other blood-pressure medicines need to be checked carefully [5].
What Is Diltiazem and Why Is It Prescribed?
Diltiazem is a prescription medicine known as a calcium channel blocker. It is commonly used to treat high blood pressure (hypertension) and angina (chest pain caused by reduced blood flow to the heart). Diltiazem works by relaxing and widening blood vessels, which lowers blood pressure and reduces the workload on the heart. This helps to prevent angina attacks and can reduce the risk of stroke and heart attack in people with high blood pressure.
Diltiazem is usually taken once or twice a day, depending on the formulation (standard or modified-release tablets). Common side effects include ankle swelling, headache, flushing, and dizziness, particularly when standing up. Because diltiazem lowers blood pressure, combining it with other medicines that have the same effect requires careful monitoring.
Diltiazem also affects the way the liver breaks down certain medicines. It is a moderate inhibitor of an enzyme called CYP3A4, which means it can increase the levels of some medicines in the bloodstream, including vardenafil. This is an important consideration when the two medicines are used together.
At a glance
How Do Vardenafil and Diltiazem Interact?
When you take vardenafil and diltiazem together, there are two main interactions to be aware of. First, both medicines can lower blood pressure. Vardenafil relaxes blood vessels in the penis and can have a mild blood-pressure-lowering effect throughout the body. Diltiazem also lowers blood pressure by relaxing blood vessels. When taken together, the combined effect may cause dizziness, light-headedness, or fainting, especially when you stand up quickly [5].
Second, diltiazem can increase the levels of vardenafil in your bloodstream. Diltiazem slows down the enzyme (CYP3A4) that breaks down vardenafil in the liver, which means vardenafil stays in your system longer and at higher concentrations [5]. This can increase the risk of side effects such as headache, flushing, or a drop in blood pressure.
Despite these interactions, vardenafil and diltiazem can often be prescribed together safely. Your prescriber will usually start you on a lower dose of vardenafil (often 5 mg) and monitor how you respond. It is important that your diltiazem dose is stable and that your blood pressure is well controlled before starting vardenafil. Never adjust the dose of either medicine yourself, and always tell your prescriber about all the medicines you are taking [5].
The Mechanism in Plain English
Think of your liver as a factory that breaks down medicines so your body can clear them out. Diltiazem slows down one of the production lines (the CYP3A4 enzyme) that processes vardenafil. This means vardenafil hangs around in your system longer and at higher levels than it would on its own. At the same time, both medicines tell your blood vessels to relax, so the combined effect on blood pressure is stronger. Your prescriber accounts for both of these effects by starting you on a lower dose of vardenafil and checking that your blood pressure is stable.
What Your Prescriber Will Check Before Prescribing Vardenafil and Diltiazem
Before prescribing vardenafil to someone taking diltiazem, your doctor or pharmacist will carry out a thorough assessment. They will review your full medication list to check for any other interactions, particularly with medicines that are never safe to combine with vardenafil, such as nitrates (GTN spray, isosorbide mononitrate), nicorandil, or riociguat [5]. If you are taking any of these, vardenafil cannot be prescribed.
Your prescriber will ask about your cardiovascular health, including your blood pressure readings, any history of heart attack, stroke, or angina, and whether your heart condition is stable. They will check that your diltiazem dose has been stable for a while and that your blood pressure is well controlled. If your blood pressure is too low or unstable, vardenafil may not be suitable [5].
They will also ask about other medical conditions, such as liver or kidney problems, any history of priapism (prolonged erection), retinal disorders, or sudden vision or hearing loss. Your prescriber will explain the signs of serious side effects and advise you to start on the lowest effective dose of vardenafil (usually 5 mg if you are taking diltiazem). You should never take more than the prescribed dose or take vardenafil more than once a day [5].
Online Consultations at Cured Pharmacy
At Cured Pharmacy, all prescription medicines, including vardenafil, are supplied only after an online consultation reviewed by a UK-registered prescriber. During the consultation, you will be asked detailed questions about your current medicines (including diltiazem), your medical history, and your blood pressure. The prescriber will decide whether vardenafil is safe and appropriate for you, and if so, which dose to start with. This ensures that the interaction between vardenafil and diltiazem is managed safely and that you receive the right treatment for your needs.
Start Low, Go Slow
If you are taking diltiazem, your prescriber will usually start you on 5 mg vardenafil to minimise the risk of side effects. Do not increase the dose yourself—always discuss any changes with your prescriber first.
Practical Advice for Taking Vardenafil and Diltiazem Safely
If your prescriber has approved the combination of vardenafil and diltiazem, there are several practical steps you can take to use them safely. First, always start with the lowest dose of vardenafil (usually 5 mg) and do not increase the dose without consulting your prescriber. Take vardenafil about 25 to 60 minutes before sexual activity, and remember that it needs sexual stimulation to work [5].
Be aware of the signs of low blood pressure, such as dizziness, light-headedness, or feeling faint, especially when you stand up. If you experience these symptoms, sit or lie down until they pass, and mention them to your prescriber at your next review. Avoid drinking large amounts of alcohol when taking vardenafil, as alcohol can lower blood pressure further and make erectile dysfunction worse [5].
Do not take vardenafil with grapefruit or grapefruit juice, as grapefruit can increase the levels of vardenafil in your blood and raise the risk of side effects. Keep taking your diltiazem exactly as prescribed—do not stop or change the dose without medical advice. If you are prescribed any new medicines, always tell the prescriber or pharmacist that you are taking both vardenafil and diltiazem so they can check for further interactions [5].
Warning Signs and When to Seek Urgent Help
Most men taking vardenafil and diltiazem together do not experience serious problems, but it is important to know the warning signs that require urgent medical attention. If you develop chest pain during or after sexual activity, stop what you are doing and seek immediate medical help. Do not take any nitrate medicines (such as GTN spray) if you have used vardenafil, as this combination can cause a dangerous drop in blood pressure [5].
If you have an erection that lasts longer than four hours (priapism), go to A&E straight away. Priapism is a medical emergency and can cause permanent damage to the penis if not treated promptly. 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 also emergencies—stop taking vardenafil and seek medical help immediately [5].
If you experience severe dizziness, fainting, or a very fast or irregular heartbeat, contact your GP or call NHS 111 for advice. These symptoms may indicate that your blood pressure has dropped too low. Always keep your prescriber informed of any side effects or concerns, and attend regular blood pressure checks as advised. If you are unsure whether a symptom is serious, it is always better to seek advice [5].
What to Do If You Miss a Dose of Diltiazem
If you miss a dose of diltiazem, take it as soon as you remember, unless it is nearly time for your next dose. In that case, skip the missed dose and take the next one at the usual time. Do not take a double dose to make up for a forgotten one. If you are unsure, contact your pharmacist or GP for advice. Keep taking your diltiazem regularly to keep your blood pressure stable, as this is important for the safe use of vardenafil.
When to get urgent help
- Chest pain during or after sexual activity—seek immediate medical help and do not take nitrates
- An erection lasting longer than four hours (priapism)—go to A&E straight away
- Sudden loss of vision in one or both eyes—stop vardenafil and seek urgent medical attention
- Sudden decrease or loss of hearing, possibly with ringing in the ears or dizziness—stop vardenafil and get help
- Severe dizziness, fainting, or very fast or irregular heartbeat—contact your GP or call NHS 111
Call 999 or go to A&E in an emergency, or contact NHS 111 for urgent advice.
Scientific References
- Joint Formulary Committee. (n.d.). Sildenafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/sildenafil/ [accessed 29 October 2026]
- Joint Formulary Committee. (n.d.). Tadalafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/tadalafil/ [accessed 29 October 2026]
- Joint Formulary Committee. (n.d.). Vardenafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/vardenafil/ [accessed 29 October 2026]
- NHS. (n.d.). Erectile dysfunction (impotence). https://www.nhs.uk/conditions/erection-problems-erectile-dysfunction/ Accessed 29 October 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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Common Questions
Can't find your answer? Our UK pharmacists review every consultation and can help.
Can I take vardenafil if I am on diltiazem?
Yes, vardenafil can often be prescribed safely with diltiazem, but your prescriber will usually start you on a lower dose (5 mg) and check that your blood pressure is stable. Both medicines can lower blood pressure, and diltiazem increases vardenafil levels, so careful monitoring is needed.
Why does diltiazem affect vardenafil levels?
Diltiazem slows down the liver enzyme (CYP3A4) that breaks down vardenafil, so vardenafil stays in your system longer and at higher concentrations. This can increase the risk of side effects, which is why a lower starting dose is usually recommended.
What dose of vardenafil should I take if I am on diltiazem?
Your prescriber will usually start you on 5 mg vardenafil if you are taking diltiazem. Do not increase the dose without consulting your prescriber, as higher doses may increase the risk of side effects.
Can I drink grapefruit juice while taking vardenafil and diltiazem?
No, you should avoid grapefruit and grapefruit juice, as grapefruit can further increase vardenafil levels in your blood and raise the risk of side effects. Stick to other fruit juices or water.
What should I do if I feel dizzy after taking vardenafil with diltiazem?
Sit or lie down until the dizziness passes. Dizziness can be a sign of low blood pressure. If it happens repeatedly or is severe, contact your GP or pharmacist for advice, as your doses may need adjusting.
Are there any blood pressure medicines I cannot take with vardenafil?
Yes, you must never take vardenafil with nitrates (such as GTN spray or isosorbide mononitrate), nicorandil, or riociguat, as this combination can cause a dangerous drop in blood pressure. Diltiazem is safe to use with vardenafil under prescriber supervision.
How long does vardenafil stay in my system if I am taking diltiazem?
Diltiazem slows the breakdown of vardenafil, so it stays in your system longer than it would on its own. This is why a lower dose is recommended and why you should not take vardenafil more than once a day.
Can I take other ED medicines if vardenafil does not work with diltiazem?
If vardenafil is not suitable or effective for you, your prescriber may consider other PDE5 inhibitors such as sildenafil or tadalafil. All PDE5 inhibitors interact with diltiazem to some degree, so your prescriber will choose the most appropriate option and dose for you.
Medically reviewed by
Tarun Kumar, Superintendent Pharmacist (GPhC 2233073)