Tadalafil and Terbinafine: Can You Take Them Together?

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At a glance

What is tadalafil and what is it used for?

Tadalafil is a prescription medicine used to treat erectile dysfunction (ED) in adult men. It belongs to a group of medicines called phosphodiesterase type 5 (PDE5) inhibitors, which work by relaxing blood vessels in the penis, allowing increased blood flow when you are sexually aroused [3][4].

Tadalafil is available in two 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 every day at the same time. Both require sexual stimulation to work—tadalafil does not cause an automatic erection [4].

In the UK, tadalafil is the generic version of Cialis. It is only supplied after an online or face-to-face consultation with a prescriber, who will check your medical history, current medicines, and whether tadalafil is safe for you. At Cured Pharmacy, all prescriptions are reviewed by UK-registered prescribers before dispensing.

What is terbinafine and what is it used for?

Terbinafine is an antifungal medicine used to treat fungal infections of the skin and nails. It is commonly prescribed for conditions such as athlete's foot, ringworm, jock itch, and fungal nail infections (onychomycosis). Terbinafine works by stopping the growth of fungi, helping to clear the infection over time.

Terbinafine is available as tablets (usually 250mg once daily) for more serious or widespread infections, and as a cream or gel for topical use on the skin. Tablet courses typically last several weeks for skin infections and several months for nail infections, as nails grow slowly and the medicine needs time to work.

Because terbinafine tablets are taken over a long period, it is important to tell your prescriber about all other medicines you are taking, including those for erectile dysfunction. This allows them to check for any potential interactions and adjust treatment if needed.

Do tadalafil and terbinafine interact with each other?

No major interaction between tadalafil and terbinafine is commonly reported in standard drug interaction databases. Terbinafine does not significantly affect the liver enzymes (CYP3A4) that break down tadalafil, so it is unlikely to raise or lower tadalafil levels in your body in a clinically meaningful way.

However, it is important to remember that every person is different, and your prescriber will review your full medical history and all current medicines—including terbinafine—during the consultation. This ensures that tadalafil is safe for you and that there are no other health conditions or medicines that might cause concern.

If you are taking terbinafine tablets for a fungal infection and are considering treatment for erectile dysfunction, you should declare this during your online consultation. Your prescriber will confirm that the combination is appropriate and advise you on the safest way to use tadalafil alongside your antifungal treatment.

How tadalafil is broken down in the body

Tadalafil is mainly broken down by an enzyme in the liver called CYP3A4. Medicines that strongly inhibit (block) this enzyme—such as ritonavir, ketoconazole, itraconazole, and clarithromycin—can raise tadalafil levels and increase the risk of side effects. In these cases, your prescriber will reduce the maximum dose of tadalafil [4].

Terbinafine does not strongly inhibit CYP3A4, so it is not expected to cause a significant rise in tadalafil levels. This is why the combination is generally considered safe, though your prescriber will always check your individual circumstances before prescribing.

What you need to know

• No major interaction is commonly reported between tadalafil and terbinafine.
• Always declare terbinafine during your consultation so your prescriber can confirm tadalafil is safe for you.
• Ketoconazole and itraconazole require a reduced tadalafil dose, but terbinafine does not.
• Seek urgent help if you experience chest pain, sudden vision loss, or an erection lasting over four hours.
• See your GP if you have new erectile dysfunction, as it can signal underlying health conditions.

What does your prescriber check before prescribing tadalafil?

Before prescribing tadalafil, your prescriber will ask about your medical history, including any heart conditions, blood pressure problems, liver or kidney disease, eye conditions, and any medicines you are currently taking. This includes prescription medicines, over-the-counter treatments, and herbal supplements [2][4].

Certain medicines must never be taken with tadalafil because they can cause a dangerous drop in blood pressure. These include nitrates (such as GTN spray, isosorbide mononitrate), nicorandil, riociguat, and recreational drugs called 'poppers' (amyl or alkyl nitrites). If you take any of these, you cannot use tadalafil [4].

Your prescriber will also check for medicines that can interact with tadalafil, such as alpha-blockers (for prostate or blood pressure), potent CYP3A4 inhibitors, and other blood-pressure-lowering medicines. If you are taking terbinafine, you should mention this during the consultation, even though no major interaction is expected. The prescriber will confirm that tadalafil is safe for you and recommend the most appropriate dose and schedule.

Medicines that must not be taken with tadalafil

Do not take tadalafil if you are using nitrates (GTN spray, isosorbide mononitrate or dinitrate), nicorandil, riociguat, or recreational 'poppers'. The combination can cause a severe and potentially life-threatening fall in blood pressure [4].

You must also not take tadalafil together with another PDE5 inhibitor (such as sildenafil, vardenafil, or avanafil) on the same day. Using two ED medicines at once does not improve effectiveness and increases the risk of side effects.

Practical advice for taking tadalafil and terbinafine together

If your prescriber confirms that tadalafil is suitable for you and you are already taking terbinafine, you can usually take both medicines as prescribed. There is no need to separate the doses by a specific time, though it is sensible to follow the instructions for each medicine individually.

For on-demand tadalafil (10mg or 20mg), take one tablet at least 30 minutes before sexual activity. Do not take more than one dose in 24 hours. For daily tadalafil (2.5mg or 5mg), take one tablet at the same time each day, whether or not you plan to have sex. Continue taking your terbinafine tablets exactly as your doctor has prescribed, usually once daily with or after food.

If you experience any unusual symptoms after starting tadalafil—such as dizziness, chest pain, sudden vision or hearing loss, or an erection lasting more than four hours—seek medical help immediately. These are rare but serious side effects that require urgent attention [4]. Always read the patient information leaflet that comes with your medicine and contact your prescriber or pharmacist if you have any questions.

When to get urgent help

• Erection lasting more than 4 hours (priapism)—go to A&E immediately
• Sudden loss of vision in one or both eyes—stop tadalafil and seek urgent medical help
• Sudden decrease or loss of hearing, sometimes with ringing in the ears or dizziness
• Chest pain during or after sex—do not use nitrates; call 999 and tell them you have taken tadalafil
• Severe allergic reaction (swelling of face, lips, tongue, or throat, difficulty breathing)—call 999

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

When to see your GP about erectile dysfunction

If you are experiencing erectile dysfunction for the first time, it is important to see your GP for a full assessment. ED can be an early warning sign of underlying health conditions such as heart disease, high blood pressure, or diabetes, and your GP can arrange tests and discuss treatment options [1][2].

Your GP will ask about your symptoms, lifestyle, and medical history, and may check your blood pressure, blood sugar, and cholesterol levels. They can also review any medicines you are taking—including terbinafine—and refer you to a specialist if needed. Treating the underlying cause can sometimes improve ED without the need for additional medication.

If your GP confirms that ED treatment is appropriate, you can access prescription medicines such as tadalafil through your GP, a local pharmacy, or a registered online pharmacy like Cured Pharmacy. Our service includes a confidential online consultation reviewed by a UK prescriber, with discreet delivery to your door. All consultations are reviewed individually to ensure the treatment is safe and suitable for you.

Why tadalafil requires a prescription

Tadalafil is a prescription-only medicine because it can interact with other treatments and is not safe for everyone. Men with certain heart conditions, very low blood pressure, recent stroke or heart attack, or those taking nitrates or nicorandil cannot use tadalafil [4].

The online consultation at Cured Pharmacy allows a UK prescriber to review your medical history, current medicines (including terbinafine), and overall health before approving treatment. This ensures you receive the right medicine at the right dose, with clear advice on how to use it safely.