Tadalafil and Degarelix: Can They Be Taken Together?
Learn about the interaction, safety checks, and what your prescriber reviews before combining these medicines.
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Tadalafil and Degarelix: Understanding the Interaction
Published: 20 October 2026
Many men wonder whether tadalafil and degarelix can be taken together safely. The good news is that no major direct interaction between tadalafil (a medicine for erectile dysfunction) and degarelix (a hormone therapy used mainly for prostate cancer) is commonly reported in clinical practice. However, both medicines affect your body in different ways, and your prescriber will need to review your full medical history and current health before confirming that tadalafil is suitable for you.
Tell Every Prescriber About Both Medicines
Always inform any doctor, pharmacist, or healthcare professional that you are taking both tadalafil and degarelix, especially if you need emergency treatment or new medicines are started. This ensures your safety and helps avoid dangerous drug interactions.
What Is Tadalafil and How Does It Work?
Tadalafil is a prescription medicine used to treat erectile dysfunction (ED). It belongs to a group of medicines called PDE5 inhibitors, which work by relaxing blood vessels in the penis, allowing increased blood flow when you are sexually aroused [3][4]. Tadalafil is the active ingredient in branded Cialis and is also available as a generic medicine at lower cost.
Tadalafil is available in two main forms: on-demand tablets (usually 10mg or 20mg) taken at least 30 minutes before sexual activity, with effects lasting up to 36 hours; and daily low-dose tablets (2.5mg or 5mg) taken once a day to allow spontaneity [4]. All PDE5 inhibitors, including tadalafil, require sexual stimulation to work—they do not cause an automatic erection.
Common side effects include headache, indigestion, back pain, muscle aches, flushing, and nasal congestion [4]. These are usually mild and temporary. Tadalafil is only supplied after an online or face-to-face consultation reviewed by a UK-registered prescriber, who will check that it is safe and appropriate for you.
What Is Degarelix and Why Is It Prescribed?
Degarelix is a prescription medicine used primarily to treat advanced prostate cancer. It is a type of hormone therapy known as a gonadotropin-releasing hormone (GnRH) receptor antagonist [12]. Degarelix works by blocking the production of testosterone, a male hormone that can fuel the growth of prostate cancer cells.
The medicine is given as an injection under the skin, usually once a month, by a healthcare professional. By lowering testosterone levels, degarelix can help slow the progression of prostate cancer. However, reduced testosterone can also contribute to erectile dysfunction, which is why some men on degarelix seek treatment for ED [1][2].
Side effects of degarelix can include hot flushes, weight gain, fatigue, and injection-site reactions. Because it significantly lowers testosterone, many men experience a reduction in libido and difficulty achieving or maintaining erections. This is where ED treatments such as tadalafil may be considered, provided they are safe to use alongside degarelix.
Why Men on Degarelix May Experience ED
Testosterone plays an important role in sexual desire and erectile function. Degarelix deliberately lowers testosterone to treat prostate cancer, and this hormonal change can lead to erectile dysfunction in many men [1][2]. ED during hormone therapy is common and does not mean the cancer treatment is failing—it is a recognised side effect of lowering testosterone levels.
When to get urgent help
- Erection lasting more than 4 hours (priapism)—go to A&E or call 999 immediately
- Sudden loss of vision in one or both eyes—seek urgent medical attention
- Sudden decrease or loss of hearing, possibly with ringing in the ears or dizziness
- Chest pain during or after sexual activity—stop and seek help; do not take nitrates if you have used tadalafil in the past 48 hours
- Severe dizziness, fainting, or feeling very unwell after taking tadalafil—sit or lie down and call 111 or your GP
Call 999 or go to A&E in an emergency, or contact NHS 111 for urgent advice.
The Interaction Between Tadalafil and Degarelix
No major direct pharmacological interaction between tadalafil and degarelix is commonly reported in clinical practice or standard drug interaction databases [3][4][12]. This means that tadalafil does not interfere with how degarelix works to lower testosterone, and degarelix does not significantly alter the way tadalafil is broken down or eliminated from the body.
However, the underlying reason for taking degarelix—advanced prostate cancer—means your prescriber will need to carefully assess your overall health, heart function, and fitness for sexual activity before prescribing tadalafil [2]. Sexual activity itself places demands on the heart, and some men with serious health conditions may be advised that sexual activity is not recommended.
Your prescriber will also review all your other medicines, because tadalafil can interact with certain drugs such as nitrates, alpha-blockers, and medicines that affect liver enzymes [3][4]. Even though tadalafil and degarelix do not directly interact, a full medication review is essential to ensure safety.
What Your Prescriber Will Check Before Prescribing Tadalafil and Degarelix Together
Before prescribing tadalafil to someone taking degarelix, a UK prescriber will review your full medical history, current medicines, and overall health. They will check whether you have any conditions that make PDE5 inhibitors unsuitable, such as recent heart attack or stroke, unstable angina, severe heart failure, very low blood pressure, or previous sudden vision loss (NAION) [2][3][4].
The prescriber will ask about all your current medicines, including over-the-counter products and supplements. Tadalafil must never be taken with nitrates (such as GTN spray or isosorbide mononitrate), nicorandil, riociguat, or recreational drugs called 'poppers', because the combination can cause a dangerous drop in blood pressure [3][4]. If you take alpha-blockers for urinary symptoms (common in men with prostate conditions), the prescriber will ensure you are stable on that medicine and may start you on a lower dose of tadalafil.
Your prescriber will also consider whether sexual activity is advisable given your cancer diagnosis and general fitness. If tadalafil is deemed safe, they will choose the most appropriate dose and form (on-demand or daily) based on your needs and preferences [2][4].
Medicines That Must Not Be Taken with Tadalafil
Do not take tadalafil together with nitrates (GTN spray, isosorbide mononitrate or dinitrate), nicorandil, riociguat, amyl or alkyl nitrites ('poppers'), or another PDE5 inhibitor (such as sildenafil or vardenafil) [3][4]. Combining these medicines can cause a serious and potentially life-threatening fall in blood pressure. Always tell your prescriber about every medicine you take, including those bought over the counter or online.
At a glance
Practical Advice for Taking Tadalafil While on Degarelix
If your prescriber confirms that tadalafil is safe for you, take it exactly as directed. For on-demand tadalafil (10mg or 20mg), take one tablet at least 30 minutes before sexual activity; the effect can last up to 36 hours, so you do not need to time it precisely [4]. For daily tadalafil (2.5mg or 5mg), take one tablet at the same time each day, allowing you to be ready for sexual activity at any time.
Remember that tadalafil requires sexual stimulation to work—it will not cause an erection on its own. Because degarelix lowers testosterone, you may notice reduced libido or less spontaneous desire; tadalafil can help with the physical aspect of achieving an erection, but it does not restore testosterone levels or sexual desire [1][2]. Some men find that combining ED treatment with psychological support or counselling is helpful.
Avoid drinking large amounts of alcohol, as this can worsen erectile dysfunction and increase the risk of dizziness or low blood pressure when taking tadalafil [4]. Grapefruit juice can raise tadalafil levels in the blood, so it is best to avoid it. If you experience side effects such as severe headache, dizziness, or visual disturbances, speak to your pharmacist or doctor. Do not take more than the prescribed dose, and do not take tadalafil more often than once a day if using the on-demand form.
When to Seek Urgent Medical Help with Tadalafil and Degarelix
Although serious side effects are uncommon, you should seek urgent medical help if you experience an erection lasting more than four hours (priapism), as this can cause permanent damage if not treated promptly [3][4]. Go to A&E or call 999 immediately if this happens.
Seek urgent help if you have sudden loss of vision in one or both eyes, or sudden decrease or loss of hearing, which may be accompanied by ringing in the ears or dizziness [3][4]. These are rare but serious side effects. If you develop chest pain during or after sexual activity, stop and seek medical advice—do not take nitrate medicines (such as GTN spray) if you have used tadalafil in the past 48 hours, as this can cause a dangerous drop in blood pressure.
If you feel unwell, dizzy, or faint after taking tadalafil, sit or lie down and seek advice from your pharmacist or doctor. Always inform any healthcare professional treating you that you are taking both tadalafil and degarelix, especially in an emergency. If you have concerns about side effects or the suitability of tadalafil while on cancer treatment, discuss them with your oncologist, GP, or the prescriber who issued your ED treatment.
Reporting Side Effects and Ongoing Monitoring
If you experience side effects from tadalafil, you can report them via the Yellow Card Scheme at yellowcard.mhra.gov.uk or by asking your pharmacist for a Yellow Card form [12]. Your oncology team will continue to monitor your response to degarelix, and you should attend all scheduled appointments. If your health changes or new medicines are started, inform your ED prescriber so they can review whether tadalafil remains safe for you.
In summary
- No major direct interaction between tadalafil and degarelix is commonly reported in clinical practice
- Your prescriber will assess your overall health and fitness for sexual activity before prescribing tadalafil
- Never take tadalafil with nitrates, nicorandil, riociguat, or poppers due to dangerous blood pressure drop
- Degarelix lowers testosterone, which commonly causes ED; tadalafil helps erections but does not restore libido
- Seek urgent help for erections lasting over four hours or sudden vision or hearing loss
Scientific References
- NHS. (n.d.). Erectile dysfunction (impotence). NHS website. https://www.nhs.uk/conditions/erection-problems-erectile-dysfunction/ [accessed 20 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 20 October 2026]
- Joint Formulary Committee. (n.d.). Sildenafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/sildenafil/ [accessed 20 October 2026]
- Joint Formulary Committee. (n.d.). Tadalafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/tadalafil/ [accessed 20 October 2026]
- Joint Formulary Committee. (n.d.). Alprostadil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/alprostadil/ [accessed 20 October 2026]
- Electronic Medicines Compendium. (n.d.). Summaries of Product Characteristics and Patient Information Leaflets. https://www.medicines.org.uk/emc/ [accessed 20 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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Medically reviewed by
Tarun Kumar, Superintendent Pharmacist (GPhC 2233073)