Tadalafil and Varenicline: Can You Take Them Together?

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Tadalafil and Varenicline: Understanding the Interaction

Published: 26 October 2026

Tadalafil and varenicline are two medicines that can be prescribed together in many cases, but your prescriber will need to review your full medical history to ensure the combination is safe for you. Tadalafil (also known as Cialis) is a PDE5 inhibitor used to treat erectile dysfunction, while varenicline (Champix) is a prescription medicine that helps people stop smoking. This page explains what each medicine does, whether they interact, what your prescriber will check, and practical advice for taking them safely.

What is tadalafil and how does it work?

Tadalafil is a phosphodiesterase type 5 (PDE5) inhibitor licensed in the UK to treat erectile dysfunction (ED). It works by relaxing the blood vessels in the penis, allowing increased blood flow when you are sexually aroused [4]. Unlike some other ED treatments, tadalafil does not cause an erection on its own—sexual stimulation is still needed.

Tadalafil is available in two main forms: on-demand tablets (usually 10 mg or 20 mg taken at least 30 minutes before sexual activity) and daily low-dose tablets (2.5 mg or 5 mg taken once a day). The on-demand dose can remain effective for up to 36 hours, which is why it is sometimes called the 'weekend pill' [4]. Both branded Cialis and generic tadalafil are available on prescription after a clinical consultation with a UK prescriber.

What is varenicline and how does it work?

Varenicline (brand name Champix) is a prescription medicine used to help people stop smoking. It works by binding to nicotine receptors in the brain, reducing cravings and withdrawal symptoms while also making smoking less rewarding if you do have a cigarette [12]. Varenicline is usually started one to two weeks before your planned quit date and taken for 12 weeks, though some people may continue for longer.

Stopping smoking is one of the most important steps you can take to improve your overall health, including your cardiovascular health and erectile function. Smoking damages blood vessels and reduces blood flow, which can contribute to erectile dysfunction [1]. Many men find that their erections improve after they quit smoking, though this can take time.

Do tadalafil and varenicline interact with each other?

There is no major drug interaction commonly reported between tadalafil and varenicline. These two medicines work through different mechanisms in the body: tadalafil affects blood flow to the penis by inhibiting the PDE5 enzyme, while varenicline acts on nicotine receptors in the brain [4][12]. They are not known to interfere with each other's effectiveness or significantly increase the risk of side effects when taken together.

However, it is still essential to tell your prescriber about all medicines you are taking, including varenicline, during your consultation. Your prescriber will review your full medication list and medical history to ensure that tadalafil is safe and appropriate for you. Some men taking varenicline may experience side effects such as nausea, headache, or changes in mood, and your prescriber will consider these alongside any potential side effects of tadalafil.

Why your prescriber needs to know about all your medicines

Even though tadalafil and varenicline do not have a major interaction, your prescriber must check for other medicines or health conditions that could make tadalafil unsuitable. For example, tadalafil must never be taken with nitrates (such as GTN spray or isosorbide mononitrate), nicorandil, riociguat, or recreational drugs called 'poppers', as this combination can cause a dangerous drop in blood pressure [4]. Your prescriber will also check for other blood-pressure medicines, alpha-blockers, and certain antifungal or antiviral drugs that can affect how tadalafil works.

What will your prescriber check before prescribing tadalafil and varenicline?

Before prescribing tadalafil, your prescriber will ask about your cardiovascular health, blood pressure, and any history of heart attack, stroke, or angina. Tadalafil is not suitable if you have recently had a heart attack or stroke, have unstable angina, or have been advised that sexual activity is not safe for you [4]. Your prescriber will also check for conditions such as severe liver or kidney problems, low blood pressure, or a history of sudden vision loss (non-arteritic anterior ischaemic optic neuropathy, or NAION).

If you are taking varenicline, your prescriber will want to know how long you have been on it and whether you have experienced any side effects, particularly mood changes or cardiovascular symptoms. Varenicline has been associated with rare reports of cardiovascular events, though recent evidence suggests the benefits of quitting smoking outweigh these risks [12]. Your prescriber will consider your overall cardiovascular risk and ensure that both medicines are appropriate for you.

Declaring all your current medicines

During your online consultation, you will be asked to list all prescription medicines, over-the-counter treatments, and herbal supplements you are taking. This includes medicines for high blood pressure, prostate problems (such as alpha-blockers like tamsulosin or doxazosin), antifungals, antibiotics, and HIV treatments. Some of these can interact with tadalafil by raising its levels in the blood or adding to its blood-pressure-lowering effect [4]. Always answer these questions fully and honestly to ensure your safety.

Practical advice for taking tadalafil and varenicline together

If your prescriber approves both medicines, take each one exactly as directed. Varenicline is usually taken twice a day with food to reduce nausea, starting at a lower dose and increasing after a week [12]. Tadalafil on-demand tablets should be taken at least 30 minutes before sexual activity, with or without food, and no more than once in 24 hours. If you are prescribed daily tadalafil, take it at the same time each day, regardless of when you plan to have sex [4].

Be aware of the side effects of each medicine. Common side effects of tadalafil include headache, indigestion, back pain, muscle aches, and flushing [4]. Varenicline can cause nausea, vivid dreams, headache, and changes in mood [12]. If you experience chest pain during sex, stop immediately and seek urgent medical help. Do not take another dose of tadalafil to 'treat' chest pain, and never use GTN or other nitrate medicines while taking tadalafil.

Avoid drinking large amounts of alcohol while taking tadalafil, as alcohol can make erectile dysfunction worse and increase the risk of dizziness or low blood pressure [4]. Grapefruit juice can also raise tadalafil levels in the blood, so it is best avoided. Continue to follow your quit-smoking plan with varenicline, as stopping smoking will improve your cardiovascular health and may improve your erectile function over time [1].

When to seek medical help while taking tadalafil and varenicline

Seek urgent medical attention if you develop an erection that lasts longer than four hours (priapism), as this can cause permanent damage to the penis [4]. You should also get immediate help if you experience sudden loss of vision in one or both eyes, sudden hearing loss or ringing in the ears, or chest pain during sexual activity. If you have chest pain, do not take nitrate medicines such as GTN spray—tell the healthcare professional that you have taken tadalafil.

While taking varenicline, contact your GP or prescriber if you notice any new or worsening mood changes, agitation, depression, or thoughts of self-harm [12]. These side effects are uncommon but important to report. If you experience symptoms of an allergic reaction to either medicine—such as rash, swelling of the face or throat, or difficulty breathing—call 999 or go to A&E immediately.

If you have any questions or concerns about taking tadalafil and varenicline together, speak to your prescriber or pharmacist. Do not stop taking varenicline without advice, as this may reduce your chances of successfully quitting smoking. Similarly, if tadalafil is not working as expected or you are experiencing side effects, your prescriber can adjust the dose or suggest an alternative treatment.

Long-term benefits of quitting smoking for erectile function

Quitting smoking with the help of varenicline can have significant long-term benefits for your erectile function and overall health. Smoking damages the lining of blood vessels and reduces blood flow throughout the body, including to the penis [1]. Many men notice an improvement in their erections within weeks to months of stopping smoking, though the timeline varies. By combining varenicline to help you quit with tadalafil to manage ED in the short term, you are addressing both the symptom and one of its underlying causes.

Scientific References

1. NHS. (n.d.). Erectile dysfunction (impotence). NHS website. https://www.nhs.uk/conditions/erection-problems-erectile-dysfunction/ [accessed 26 October 2026]
2. Joint Formulary Committee. (n.d.). Tadalafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/tadalafil/ [accessed 26 October 2026]
3. Electronic Medicines Compendium. (n.d.). Summaries of Product Characteristics and Patient Information Leaflets. https://www.medicines.org.uk/emc/ [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.