Tadalafil and Bilastine: Can They Be Taken Together?

Tadalafil and Bilastine: Understanding the Interaction

Published: 18 October 2026

Many men wonder whether tadalafil and bilastine can be taken together safely. The good news is that no major interaction is commonly reported between tadalafil (used for erectile dysfunction) and bilastine (a non-sedating antihistamine for hay fever and allergies). However, every medication combination requires careful assessment, and your prescriber will review all your current medicines during your consultation to ensure tadalafil is safe and suitable for you.

What Is Tadalafil and How Does It Work?

Tadalafil is a prescription medicine used to treat erectile dysfunction (ED) in men. 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 [4]. Tadalafil is the active ingredient in branded Cialis and is also available as a generic medicine at lower cost.

Tadalafil comes 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 [4]. Both require sexual stimulation to work. Tadalafil does not cure ED or increase sexual desire; it helps you achieve and maintain an erection when you are already aroused.

Common side effects include headache, indigestion, back pain, muscle aches, flushing, and nasal congestion [4]. Most side effects are mild and temporary. Tadalafil is only available on prescription in the UK after a consultation with a qualified prescriber who will check your medical history, current medicines, and whether the treatment is safe for you.

What Is Bilastine and Why Is It Prescribed?

Bilastine is a non-sedating antihistamine used to relieve symptoms of hay fever (seasonal allergic rhinitis) and hives (urticaria). It works by blocking histamine, a substance your body releases during an allergic reaction that causes sneezing, itching, watery eyes, and runny nose. Bilastine is available on prescription and over the counter in the UK, usually as 20mg tablets taken once daily.

Unlike older antihistamines such as chlorphenamine or promethazine, bilastine is classified as non-sedating, meaning it is less likely to cause drowsiness. However, some people may still experience tiredness or dizziness. Bilastine should be taken on an empty stomach (one hour before or two hours after food) for best absorption.

Bilastine is generally well tolerated. Common side effects include headache, drowsiness, and dizziness. It does not interact with many other medicines, but your pharmacist or prescriber will always check your full medication list to ensure it is safe for you. If you are taking bilastine regularly for allergies and are considering treatment for erectile dysfunction, it is important to declare this during your consultation.

How Bilastine Differs from Other Antihistamines

Bilastine is a newer-generation antihistamine that does not cross the blood-brain barrier as easily as older types, which is why it causes less sedation. It is also less likely to interact with other medicines compared to some antihistamines that affect liver enzymes. This makes bilastine a suitable choice for people who need long-term allergy relief without significant drowsiness or drug interactions.

Can You Take Tadalafil and Bilastine Together?

No major interaction is commonly reported between tadalafil and bilastine, and many men take both medicines together without problems. Bilastine 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. Similarly, tadalafil does not interfere with how bilastine works to relieve allergy symptoms.

However, both medicines can occasionally cause dizziness or headache as side effects. If you experience these symptoms when taking tadalafil and bilastine together, they may be more noticeable, though this is not common. It is important to tell your prescriber about all medicines you take, including over-the-counter antihistamines, during your consultation.

Your prescriber will review your full medical history and current medicines to ensure tadalafil is safe for you. While the combination of tadalafil and bilastine is not known to cause serious problems, individual responses can vary. If you notice any unusual symptoms or side effects when taking both medicines, contact your GP or pharmacist for advice. Never stop or change a prescribed medicine without professional guidance.

What Your Prescriber Checks Before Approving Tadalafil

Before prescribing tadalafil, your clinician will ask about your medical history, current medicines, and overall health to ensure the treatment is safe and suitable for you [2]. They will check for conditions that make tadalafil unsuitable, such as recent heart attack or stroke, unstable angina, severe heart failure, very low blood pressure, or a history of sudden vision loss (non-arteritic anterior ischaemic optic neuropathy, or NAION).

Your prescriber will also review all your current medicines to identify any dangerous interactions. Tadalafil must never be taken with nitrates (such as GTN spray, isosorbide mononitrate, or isosorbide dinitrate), nicorandil, riociguat, or recreational drugs called 'poppers' (amyl or alkyl nitrites), as the combination can cause a life-threatening drop in blood pressure [4]. You must also not take tadalafil with another PDE5 inhibitor such as sildenafil or vardenafil.

If you take alpha-blockers for prostate symptoms or high blood pressure (such as doxazosin, tamsulosin, or alfuzosin), your 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 or fainting [4]. Medicines that strongly inhibit the liver enzyme CYP3A4 (such as ritonavir, ketoconazole, itraconazole, or clarithromycin) can raise tadalafil levels, so your dose may need to be adjusted. Always declare every medicine, supplement, and herbal remedy you use.

Why Declaring All Medicines Matters

Even medicines you buy over the counter or take occasionally can interact with tadalafil. For example, some antifungal treatments, antibiotics, and HIV medicines can affect how your body processes tadalafil. Herbal remedies such as St John's wort can make tadalafil less effective. Being open and thorough about everything you take helps your prescriber choose the safest dose and avoid potentially harmful combinations.

Practical Advice for Taking Tadalafil and Bilastine Safely

If you have been prescribed tadalafil and are also taking bilastine for allergies, take each medicine exactly as directed. Bilastine is usually taken once daily on an empty stomach (one hour before or two hours after food), while tadalafil on-demand tablets are taken at least 30 minutes before sexual activity, with or without food. If you are on daily tadalafil, take it at the same time each day, regardless of when you plan to have sex.

Avoid drinking large amounts of alcohol when taking tadalafil, as alcohol can make erectile dysfunction worse and increase the risk of dizziness and low blood pressure. Grapefruit juice can raise tadalafil levels in your blood and should be avoided. If you experience a headache or mild dizziness, stay well hydrated and avoid sudden changes in posture (such as standing up quickly).

Be aware of warning signs that require urgent medical help. If you develop an erection lasting more than four hours (priapism), sudden loss of vision or hearing, or chest pain during sexual activity, seek immediate medical attention by calling 999 or going to A&E [4]. If you have any questions or concerns about taking tadalafil and bilastine together, contact your GP or pharmacist for advice. Do not stop taking any prescribed medicine without professional guidance.

Other Medicines and Interactions with Tadalafil

While tadalafil and bilastine can usually be taken together, it is important to be aware of other medicines that do interact with tadalafil. As mentioned, you must never take tadalafil with nitrates, nicorandil, riociguat, or poppers, as this combination can cause a dangerous fall in blood pressure [4]. Do not take tadalafil with another PDE5 inhibitor such as sildenafil, vardenafil, or avanafil.

Alpha-blockers used for prostate symptoms or high blood pressure can add to the blood-pressure-lowering effect of tadalafil, increasing the risk of dizziness or fainting. If you take an alpha-blocker, your prescriber will ensure you are stable on it and may start you on the lowest dose of tadalafil [4]. Other blood-pressure medicines can also have an additive effect, though this is usually manageable with careful monitoring.

Potent CYP3A4 inhibitors, including some HIV medicines (ritonavir, cobicistat), antifungals (ketoconazole, itraconazole), and antibiotics (clarithromycin), can raise tadalafil levels, so your dose may need to be reduced [4]. CYP3A4 inducers such as rifampicin, carbamazepine, phenytoin, and St John's wort can make tadalafil less effective. Always tell your prescriber about every medicine you take, including over-the-counter products, vitamins, and herbal supplements, so they can check for interactions and adjust your treatment if needed.

When to Seek Further Advice

If you start a new medicine while taking tadalafil, check with your GP or pharmacist whether it is safe to continue. If you develop new symptoms, side effects, or your health changes, seek professional advice. Erectile dysfunction can be an early warning sign of heart disease or diabetes, so if you have not already done so, see your GP for a full health check [1][2].

Scientific References

1. NHS. (n.d.). Erectile dysfunction (impotence). NHS website. https://www.nhs.uk/conditions/erection-problems-erectile-dysfunction/ [accessed 18 October 2026]
2. National Institute for Health and Care Excellence. (n.d.). Erectile dysfunction. Clinical Knowledge Summaries. https://cks.nice.org.uk/topics/erectile-dysfunction/ [accessed 18 October 2026]
3. Joint Formulary Committee. (n.d.). Tadalafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/tadalafil/ [accessed 18 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.