Tadalafil and Goserelin: Can They Be Taken Together?

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At a glance

What is Tadalafil and How Does It Work?

Tadalafil is a prescription medicine licensed in the UK to treat erectile dysfunction in men [4]. 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. Tadalafil does not cause an erection on its own—sexual stimulation is still needed [4].

Tadalafil is available in two forms: on-demand tablets (usually 10 mg or 20 mg) taken at least 30 minutes before sexual activity, with effects lasting up to 36 hours, and daily low-dose tablets (2.5 mg or 5 mg) taken once a day at the same time [4]. The long duration of action has earned tadalafil the nickname 'the weekend pill'. Common brand names include Cialis, and generic versions are widely available at lower cost.

At Cured Pharmacy, tadalafil is available after an online consultation reviewed by a UK prescriber. The prescriber will check your medical history, current medicines, and overall health to ensure tadalafil is safe and suitable for you.

What is Goserelin and Why is It Prescribed?

Goserelin (brand name Zoladex) is a hormone therapy medicine used mainly to treat prostate cancer, although it is also used for some other conditions including endometriosis and breast cancer [12]. It belongs to a class of medicines called GnRH agonists (gonadotropin-releasing hormone agonists), which work by reducing the production of testosterone in men or oestrogen in women.

In men with prostate cancer, lowering testosterone levels can slow or stop the growth of cancer cells that depend on this hormone. Goserelin is given as an injection under the skin, usually into the abdomen, every four or twelve weeks depending on the formulation [12]. While it is highly effective for its intended purpose, the reduction in testosterone causes a range of side effects.

One of the most common and distressing side effects of goserelin in men is erectile dysfunction [2]. Because testosterone plays a key role in sexual desire and erectile function, lowering it significantly can make achieving and maintaining an erection very difficult. Many men on goserelin experience reduced libido, ED, hot flushes, fatigue, and mood changes. These effects are expected and are a direct result of the medicine doing its job—lowering testosterone—but they can significantly affect quality of life.

How Goserelin Causes Erectile Dysfunction

Goserelin causes ED by suppressing the body's natural production of testosterone, which is essential for normal erectile function and sexual desire [2]. This is not a drug interaction in the traditional sense—it is the intended pharmacological effect of the medicine. The degree of ED varies between individuals, but most men on long-term goserelin will experience some degree of sexual dysfunction. It is important to discuss these side effects with your cancer specialist or GP, as there are options to help manage them, including PDE5 inhibitors like tadalafil.

Can You Take Tadalafil and Goserelin Together?

Yes, tadalafil and goserelin can generally be taken together. There is no known major direct drug interaction between these two medicines [4][12]. Tadalafil works by improving blood flow to the penis, while goserelin works by lowering testosterone levels through a hormonal mechanism. These are different pathways, so one medicine does not directly interfere with the way the other is processed or works in the body.

However, it is important to understand that goserelin makes erectile dysfunction more likely or more severe because of its effect on testosterone [2]. Tadalafil may help improve erectile function in some men taking goserelin, but it cannot fully reverse the hormonal cause of ED. In other words, tadalafil can help with the mechanical aspect of getting an erection (blood flow), but it cannot restore the testosterone-driven libido and overall sexual function that goserelin suppresses.

Your prescriber will review your full medical history, including your cancer treatment, before prescribing tadalafil. They will check for any other medicines or health conditions that might make tadalafil unsuitable, such as recent heart problems, very low blood pressure, or use of nitrate medicines [4]. It is essential to declare all your current medicines, including goserelin and any other cancer treatments, during your consultation.

What you need to know

• Tadalafil and goserelin can generally be taken together with no major direct drug interaction.
• Goserelin lowers testosterone, which causes erectile dysfunction; tadalafil may help but cannot restore libido.
• Your prescriber will review all medicines and health conditions before prescribing tadalafil.
• Never take tadalafil with nitrates, nicorandil, riociguat, or another PDE5 inhibitor.
• If tadalafil is not effective, other ED treatments such as vacuum devices or alprostadil are available.

What Your Prescriber Will Check Before Prescribing Tadalafil

Before prescribing tadalafil to someone taking goserelin, a UK prescriber will carry out a thorough assessment [2][4]. They will ask about your cardiovascular health, because PDE5 inhibitors like tadalafil can lower blood pressure slightly and are not suitable if sexual activity itself is inadvisable (for example, after a recent heart attack or stroke, or if you have unstable angina or severe heart failure) [4].

The prescriber will also check all your current medicines. Tadalafil must never be taken with nitrates (such as GTN spray, isosorbide mononitrate or dinitrate), nicorandil, riociguat, or recreational drugs called 'poppers' (amyl or alkyl nitrites), because the combination can cause a dangerous drop in blood pressure [4]. If you take alpha-blockers for prostate symptoms (such as tamsulosin or doxazosin), the prescriber will ensure you are stable on that medicine and may start you on a lower dose of tadalafil to reduce the risk of dizziness [4].

Your prescriber will also consider any other medicines that might interact with tadalafil, such as potent CYP3A4 inhibitors (for example, ritonavir, ketoconazole, clarithromycin), which can raise tadalafil levels and require dose adjustments [4]. They will ask about your cancer treatment plan and liaise with your oncologist if needed. Finally, they will discuss realistic expectations: tadalafil may help with erections, but it cannot restore libido or reverse the hormonal effects of goserelin.

Declaring All Your Medicines

It is vital to tell your prescriber about every medicine you take, including prescription medicines, over-the-counter products, herbal remedies, and recreational drugs. This includes goserelin, any chemotherapy or other cancer treatments, blood pressure medicines, and medicines for prostate symptoms. Never stop or change a prescribed medicine without speaking to your doctor or pharmacist first.

Practical Advice for Taking Tadalafil with Goserelin

If your prescriber approves tadalafil while you are on goserelin, start with the lowest effective dose and follow the instructions carefully [4]. On-demand tadalafil (10 mg or 20 mg) should be taken at least 30 minutes before sexual activity, and you should not take it more than once a day. Daily tadalafil (2.5 mg or 5 mg) is taken at the same time every day, regardless of when you plan to have sex [4].

Remember that tadalafil requires sexual stimulation to work—it will not cause an automatic erection [4]. Because goserelin lowers libido, you may find that sexual desire is reduced even if tadalafil helps with the physical ability to achieve an erection. Open communication with your partner and realistic expectations are important. Some men find that counselling or psychosexual therapy can be helpful alongside medicine [2].

Avoid drinking large amounts of alcohol, as this can make erectile dysfunction worse and increase the risk of side effects such as dizziness or headache [4]. Grapefruit juice can raise tadalafil levels in the blood, so it is best avoided. If you experience side effects such as headache, indigestion, back pain, or flushing, these are usually mild and temporary [4]. However, if you develop chest pain during sex, a prolonged erection lasting more than four hours, or sudden loss of vision or hearing, seek urgent medical help.

When to get urgent help

• Erection lasting more than 4 hours (priapism) – go to A&E immediately
• Sudden loss of vision or hearing – stop tadalafil and seek urgent medical help
• Chest pain during or after sexual activity – call 999
• Severe dizziness, fainting, or feeling very unwell after taking tadalafil – call 111 or see your GP urgently
• New or worsening symptoms related to your cancer treatment – contact your oncologist or specialist nurse

Call 999 or go to A&E in an emergency, or contact NHS 111 for urgent advice.

Other Options and When to Seek Further Help

If tadalafil does not provide sufficient benefit, or if it is not suitable for you, there are other treatment options for erectile dysfunction [2]. Other PDE5 inhibitors such as sildenafil (Viagra), vardenafil (Levitra), or avanafil (Spedra) work in a similar way and may be tried, though they are also unlikely to fully overcome the hormonal effects of goserelin [3][5][6]. Never take more than one PDE5 inhibitor at the same time.

For men who do not respond to tablets, other treatments include vacuum erection devices, alprostadil cream (Vitaros) applied to the tip of the penis, or alprostadil injections (Caverject) into the side of the penis [7]. These options work by different mechanisms and may be more effective when testosterone is very low. Penile implants are a surgical option for men with severe, treatment-resistant ED [2].

It is important to discuss erectile dysfunction openly with your cancer specialist or GP [1][2]. ED during goserelin treatment is common and expected, and healthcare professionals are used to these conversations. They can refer you to a specialist urology or sexual health service if needed. If you experience new or worsening symptoms such as chest pain, severe dizziness, fainting, or any concerns about your cancer treatment, contact your doctor promptly. At Cured Pharmacy, our pharmacists are available to answer questions about your ED treatment and can liaise with your GP or specialist if needed.

Talking to Your Healthcare Team

Do not be embarrassed to raise concerns about sexual function with your doctor or oncologist. Erectile dysfunction is a recognised and common side effect of goserelin, and your healthcare team can offer support, adjust your treatment plan if possible, or refer you for specialist help [2]. Your quality of life matters, and there are options available to help manage this side effect.

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