Tadalafil and Tamoxifen: Can They Be Taken Together?
Learn how these medicines interact and what your UK prescriber will check during your consultation.
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Tadalafil and Tamoxifen: What You Need to Know About Taking Them Together
Published: 26 October 2026
Many men want to know whether tadalafil and tamoxifen can be taken together safely. The good news is that no major direct interaction between tadalafil (a medicine for erectile dysfunction) and tamoxifen (a hormone therapy used mainly in breast cancer treatment) is commonly reported in clinical practice. However, every person's situation is different, and your prescriber or pharmacist will review all your current medicines during your consultation to ensure tadalafil is suitable for you.
Key takeaways
- No major direct interaction is commonly reported between tadalafil and tamoxifen.
- Your prescriber reviews all your medicines, health conditions, and cancer treatment during consultation.
- Tadalafil must not be taken with nitrates, nicorandil, riociguat, or poppers.
- Report chest pain during sex, sudden vision or hearing loss, or erections lasting over 4 hours immediately.
- Always declare all medicines, including over-the-counter and herbal products, to your prescriber.
What Is Tadalafil and How Does It Work?
Tadalafil is a prescription medicine used to treat erectile dysfunction (ED) in men [3][4]. It belongs to a group of medicines called PDE5 inhibitors, which work by relaxing the blood vessels in the penis, allowing more blood to flow in when you are sexually aroused. This helps you get and keep an erection suitable for sexual activity.
Tadalafil is the active ingredient in branded Cialis and is also available as a generic medicine at a lower cost. It comes in two main forms: on-demand tablets (usually 10mg or 20mg, taken at least 30 minutes before sex, with effects lasting up to 36 hours) and daily tablets (2.5mg or 5mg, taken once a day at the same time) [4]. Unlike some other ED medicines, tadalafil's long duration of action means you do not need to time it as precisely, which many men find convenient.
It is important to remember that tadalafil will not work without sexual stimulation—it does not cause an automatic erection. It simply makes it easier for your body to respond naturally when you are aroused. Tadalafil is only available on prescription in the UK after a consultation with a qualified prescriber, who will check your medical history and current medicines to ensure it is safe for you.
What Is Tamoxifen and Why Is It Prescribed?
Tamoxifen is a prescription medicine most commonly used as hormone therapy in the treatment and prevention of certain types of breast cancer, particularly those that are oestrogen-receptor-positive. It works by blocking the effects of oestrogen in breast tissue, which can slow or stop the growth of cancer cells that need oestrogen to grow.
Although tamoxifen is primarily prescribed for breast cancer in women, it is occasionally used in men for breast cancer or other conditions such as gynaecomastia (enlarged breast tissue). Tamoxifen is usually taken as a tablet once or twice a day, and treatment may continue for several years depending on the individual's condition and response.
Because tamoxifen is a long-term treatment for a serious condition, it is essential that you continue taking it exactly as your oncologist or specialist has prescribed. If you are considering starting a new medicine such as tadalafil for erectile dysfunction, you should never stop or change your tamoxifen dose without first speaking to your cancer specialist or GP. Your prescriber will take your full medical history into account during your ED consultation.
At a glance
Do Tadalafil and Tamoxifen Interact?
The question of whether tadalafil and tamoxifen interact is an important one, and the reassuring answer is that no major direct interaction between these two medicines is commonly reported in clinical practice or standard drug interaction databases. This means that, in general, taking tadalafil for erectile dysfunction while you are on tamoxifen is not expected to cause a significant problem due to a direct drug-to-drug interaction.
However, 'no major interaction reported' does not mean that tadalafil is automatically suitable for everyone taking tamoxifen. Your overall health, other medicines you may be taking, and the nature of your cancer treatment all play a role in whether tadalafil is safe and appropriate for you. For example, some cancer treatments can affect your heart or blood pressure, and tadalafil can lower blood pressure slightly. Your prescriber will review your full medical history, including your cancer diagnosis, current treatment, and any other health conditions, during your consultation.
It is also worth noting that erectile dysfunction can sometimes occur as a side effect of cancer treatment, the emotional impact of a cancer diagnosis, or other medicines you may be taking alongside tamoxifen. Your prescriber will consider all these factors and may liaise with your oncologist or GP if needed to ensure that starting tadalafil is safe and in your best interest. Always be open and honest about all your medicines and health conditions during your consultation.
Why Your Prescriber Needs to Know About All Your Medicines
Even though tadalafil and tamoxifen do not have a major direct interaction, your prescriber must know about every medicine you take—prescription, over-the-counter, herbal, and supplements. This is because tadalafil does have serious interactions with certain other medicines (such as nitrates, nicorandil, and riociguat), and some medicines can affect how tadalafil works or increase the risk of side effects.
For example, if you are taking other medicines for high blood pressure or heart conditions alongside your cancer treatment, these may add to the blood-pressure-lowering effect of tadalafil, increasing the risk of dizziness or fainting. Your prescriber will check for these interactions and adjust your treatment plan accordingly. This is why a thorough consultation is essential before starting any ED medicine.
What Does Your Prescriber Check Before Prescribing Tadalafil?
Before prescribing tadalafil, your UK prescriber will carry out a detailed consultation to ensure the medicine is safe and suitable for you. This includes reviewing your full medical history, current medicines (including tamoxifen and any other cancer treatments), and any health conditions you have. The prescriber will ask about your heart health, blood pressure, liver and kidney function, and whether you have had any recent heart attacks, strokes, or other serious cardiovascular events [2][4].
Tadalafil is not suitable for everyone. It must not be taken if you are using nitrates (such as GTN spray or isosorbide mononitrate for angina), nicorandil, riociguat, or recreational drugs known as 'poppers' (amyl or alkyl nitrites), because the combination can cause a dangerous drop in blood pressure [4]. Your prescriber will also check whether sexual activity is safe for you, as it can put extra strain on your heart. If you have unstable angina, severe heart failure, very low blood pressure, or have had a recent heart attack or stroke, tadalafil may not be appropriate.
If you are taking other medicines that can interact with tadalafil—such as alpha-blockers for prostate problems (like tamsulosin or doxazosin), certain antifungals or antibiotics, or HIV medicines—your prescriber will adjust your dose or advise whether tadalafil is safe. The prescriber may also ask about your vision and hearing, as tadalafil is not suitable for men who have had a previous episode of sudden vision loss (NAION) or certain inherited eye conditions. This thorough assessment ensures that tadalafil is prescribed safely and effectively.
Special Considerations for Men Undergoing Cancer Treatment
If you are currently undergoing cancer treatment, your prescriber will take extra care to ensure that starting tadalafil does not interfere with your treatment or overall health. Cancer and its treatment can sometimes affect your heart, blood vessels, energy levels, and emotional wellbeing, all of which can influence erectile function and the safety of ED medicines.
Your prescriber may ask for more information about your cancer diagnosis, the stage of your treatment, and any other medicines or therapies you are receiving. In some cases, they may contact your oncologist or GP to confirm that tadalafil is appropriate. This collaborative approach ensures that all aspects of your health are considered and that your cancer treatment remains the priority.
Always Declare Every Medicine
Even if you think a medicine is unrelated to erectile dysfunction, always tell your prescriber about everything you take—including over-the-counter products, supplements, and herbal remedies. This ensures your treatment is safe and effective.
Practical Advice for Taking Tadalafil Safely
If your prescriber decides that tadalafil is suitable for you, there are some practical steps you can take to use it safely and effectively. First, always take tadalafil exactly as prescribed. For on-demand tadalafil (10mg or 20mg), take one tablet at least 30 minutes before you plan to have sex; the effect can last up to 36 hours, so you do not need to take it every day [4]. For daily tadalafil (2.5mg or 5mg), take one tablet at the same time each day, whether or not you plan to have sex. Do not take more than one dose in 24 hours.
Remember that tadalafil only works when you are sexually aroused—it will not cause an erection on its own. Avoid drinking large amounts of alcohol, as this can make it harder to get an erection and can increase the risk of side effects such as dizziness or low blood pressure. Grapefruit juice can also raise the level of tadalafil in your blood, so it is best to avoid it while taking this medicine.
Common side effects of tadalafil include headache, indigestion, back pain, muscle aches, flushing, and a blocked or runny nose [4]. These are usually mild and go away on their own. However, if you experience chest pain during or after sex, stop sexual activity immediately and seek urgent medical help—do not take nitrates to relieve the chest pain if you have taken tadalafil, as this combination is dangerous. If you have an erection lasting more than 4 hours, sudden loss of vision or hearing, or severe dizziness, seek medical help straight away.
When to Seek Further Advice About Tadalafil and Tamoxifen
Even though no major interaction between tadalafil and tamoxifen is commonly reported, you should always seek further advice if you have any concerns or if your health changes. If you start a new medicine, develop new symptoms, or if your cancer treatment plan changes, let your prescriber or pharmacist know as soon as possible. They can review your medicines and check whether any adjustments are needed.
If you experience any unexpected side effects while taking tadalafil, or if the medicine does not seem to be working as well as you hoped, do not simply stop taking it or increase the dose on your own. Contact your prescriber or pharmacist for advice. They may be able to adjust your dose, suggest a different ED medicine, or investigate whether another factor (such as a change in your overall health or a new medicine) is affecting your response to treatment.
It is also important to see your GP if you develop new or worsening erectile dysfunction, even if you are already taking tadalafil. ED can sometimes be an early warning sign of underlying health problems such as heart disease, diabetes, or high blood pressure [1][2]. Your GP can carry out tests to check for these conditions and ensure you receive the right treatment. If you are undergoing cancer treatment, your oncologist or specialist nurse is also a valuable source of support and can discuss any concerns you have about sexual health and wellbeing.
How Cured Pharmacy Can Help
Cured Pharmacy is a GPhC-registered online pharmacy (GPhC 9012511) offering convenient access to ED treatments through a secure online consultation. Our UK-registered prescribers review your medical history and current medicines—including tamoxifen and any other treatments—to ensure that tadalafil or another ED medicine is safe and suitable for you. If approved, your medicine is dispensed by our qualified pharmacists and delivered discreetly to your door.
We understand that discussing erectile dysfunction can feel awkward, especially when you are managing a serious health condition such as cancer. Our service is designed to be confidential, professional, and supportive. If you have any questions about tadalafil, tamoxifen, or any other aspect of your treatment, our pharmacy team is here to help.
When to get urgent help
- Chest pain or discomfort during or after sexual activity—call 999 immediately.
- An erection lasting more than 4 hours (priapism)—go to A&E straight away.
- Sudden loss of vision in one or both eyes—seek urgent medical help.
- Sudden decrease or loss of hearing, sometimes with ringing or dizziness—contact a doctor immediately.
- Severe dizziness, fainting, or very low blood pressure—seek same-day medical advice.
Call 999 or go to A&E in an emergency, or contact NHS 111 for urgent advice.
Scientific References
- NHS. (n.d.). Erectile dysfunction (impotence). NHS website. https://www.nhs.uk/conditions/erection-problems-erectile-dysfunction/ [accessed 26 October 2026]
- National Institute for Health and Care Excellence. (n.d.). Erectile dysfunction. Clinical Knowledge Summaries. https://cks.nice.org.uk/topics/erectile-dysfunction/ [accessed 26 October 2026]
- Joint Formulary Committee. (n.d.). Sildenafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/sildenafil/ [accessed 26 October 2026]
- Joint Formulary Committee. (n.d.). Tadalafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/tadalafil/ [accessed 26 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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Pricing Disclaimer: Prices on some pages may not be up to date — the live pricing table below and pricing shown during consultation are official current prices and take precedence over any other figures on the site.
Common Questions
Can't find your answer? Our UK pharmacists review every consultation and can help.
Can I take tadalafil if I am on tamoxifen?
No major direct interaction between tadalafil and tamoxifen is commonly reported, so they can usually be taken together. However, your prescriber will review your full medical history, cancer treatment, and all other medicines during your consultation to ensure tadalafil is safe for you.
Will tamoxifen affect how well tadalafil works?
Tamoxifen is not known to reduce the effectiveness of tadalafil. However, erectile dysfunction can sometimes be caused or worsened by cancer treatment, stress, or other medicines, so your prescriber will consider all these factors when assessing your treatment.
Do I need to tell my oncologist that I am taking tadalafil?
It is a good idea to keep your oncologist or cancer specialist informed about all medicines you are taking, including tadalafil. Your Cured Pharmacy prescriber may also contact your oncologist or GP if needed to ensure your treatment is coordinated and safe.
Are there any ED medicines I must not take with tadalafil?
Yes. Do not take tadalafil with nitrates (GTN spray, isosorbide mononitrate), nicorandil, riociguat, poppers (amyl/alkyl nitrites), or another PDE5 inhibitor (such as sildenafil or vardenafil). These combinations can cause a dangerous drop in blood pressure.
What should I do if I get chest pain while taking tadalafil?
Stop sexual activity immediately and seek urgent medical help by calling 999. Do not take nitrates to relieve chest pain if you have taken tadalafil, as this combination is extremely dangerous.
Can I drink alcohol while taking tadalafil and tamoxifen?
Drinking large amounts of alcohol can make erectile dysfunction worse and increase the risk of side effects such as dizziness and low blood pressure when taking tadalafil. It is best to limit alcohol intake.
How long does tadalafil last?
On-demand tadalafil (10mg or 20mg) can last up to 36 hours, which is why it is sometimes called the 'weekend pill'. Daily tadalafil (2.5mg or 5mg) is taken once a day and provides continuous support for erectile function.
What if tadalafil does not work for me?
If tadalafil is not effective, contact your prescriber. They may adjust your dose, suggest trying a different PDE5 inhibitor (such as sildenafil or vardenafil), or investigate other factors that may be affecting your erectile function.
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Reviewed by UK-based prescribers · Takes under 3 minutes · Discreet Packaging
Medically reviewed by
Tarun Kumar, Superintendent Pharmacist (GPhC 2233073)