Tadalafil and Loratadine: Can You Take Them Together?

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Tadalafil and Loratadine: Understanding the Interaction

Published: 22 October 2026

Many men taking tadalafil for erectile dysfunction also use loratadine (commonly sold as Clarityn) for hay fever or allergies, and wonder whether tadalafil and loratadine can be taken together safely. The good news is that no major interaction is commonly reported between these two medicines, and they are generally considered safe to use at the same time. However, every person's medical history is unique, which is why a UK prescriber reviews all your current medicines—including over-the-counter antihistamines—during your online consultation before approving tadalafil.

What Is Tadalafil and How Does It Work?

Tadalafil is a prescription medicine used to treat erectile dysfunction (ED) in men [4]. It belongs to a group of medicines called PDE5 inhibitors, which work by relaxing the blood vessels in the penis, allowing more blood to flow in when you are sexually aroused [1]. Unlike some other ED treatments, tadalafil has a long duration of action—its effects can last up to 36 hours, which is why it is sometimes called the 'weekend pill' [4].

Tadalafil is available in two forms: on-demand tablets (usually 10mg or 20mg, taken at least 30 minutes before sexual activity) and daily tablets (2.5mg or 5mg, taken once a day at the same time) [4]. Both require sexual stimulation to work; tadalafil will not cause an erection on its own. At Cured Pharmacy, tadalafil is available from £7.95 after an online consultation reviewed by a UK prescriber, with first-order prices from £6.36 using code Ednew.

Common side effects include headache, indigestion, back pain, muscle aches, flushing, and a blocked or runny nose [4]. These are usually mild and short-lived. Tadalafil must not be taken with nitrates, nicorandil, riociguat, poppers, or another PDE5 inhibitor, as this combination can cause a dangerous drop in blood pressure [4].

What Is Loratadine and What Is It Used For?

Loratadine is a non-drowsy antihistamine used to relieve symptoms of hay fever (seasonal allergic rhinitis), year-round allergies (perennial allergic rhinitis), and skin allergies such as hives (urticaria). It works by blocking the action of histamine, a substance your body releases during an allergic reaction, which causes sneezing, itching, watery eyes, and a runny nose.

Loratadine is available over the counter in the UK under brand names such as Clarityn, and as generic loratadine tablets and liquid. The usual adult dose is 10mg once daily. Because it is classed as a non-sedating antihistamine, loratadine is less likely to make you feel drowsy compared to older antihistamines like chlorphenamine or promethazine, although drowsiness can still occur in some people.

Loratadine is generally well tolerated. Common side effects include headache, dry mouth, and tiredness. It is metabolised (broken down) in the liver, but it does not significantly interact with the enzyme systems that process tadalafil, which is one reason the two medicines can usually be taken together without concern.

How Loratadine Is Broken Down in the Body

Loratadine is processed in the liver by enzymes including CYP3A4 and CYP2D6, and is converted into an active metabolite called desloratadine. Tadalafil is also metabolised by CYP3A4 [4]. However, loratadine is not a strong inhibitor or inducer of CYP3A4, so it does not significantly alter the levels of tadalafil in your bloodstream. This is why no major interaction is expected when the two are used together.

Tadalafil and Loratadine: Is There an Interaction?

No major interaction between tadalafil and loratadine is commonly reported in clinical practice or drug interaction databases. This means that, for most men, taking loratadine for allergies while using tadalafil for erectile dysfunction should not cause problems. Neither medicine significantly affects the way the other is broken down or how it works in the body.

That said, both medicines can occasionally cause headache as a side effect. If you experience more frequent or severe headaches when taking them together, it may be worth discussing with your pharmacist or GP. Additionally, loratadine can rarely cause dizziness or drowsiness, and tadalafil can lower blood pressure slightly, which may also lead to dizziness in some men. If you feel lightheaded, avoid driving or operating machinery until you know how the combination affects you.

It is important to remember that even though no major interaction is expected, your prescriber will still review all your current medicines—including over-the-counter antihistamines—during your online consultation. This ensures that tadalafil is safe and suitable for you based on your complete medical history and any other conditions you may have.

What Your Prescriber Checks Before Approving Tadalafil

Before tadalafil can be prescribed, a UK-registered prescriber will carry out a thorough assessment of your health. This includes asking about your cardiovascular health (heart and blood pressure), any history of stroke or heart attack, liver or kidney problems, blood disorders, stomach ulcers, and any conditions affecting your eyes or penis [2][4]. You will also be asked about all the medicines you currently take, including prescription drugs, over-the-counter products like loratadine, herbal remedies, and supplements.

The prescriber will specifically check for medicines that must never be taken with tadalafil. These include nitrates (such as GTN spray or isosorbide mononitrate), nicorandil, riociguat, and recreational drugs known as poppers (amyl or alkyl nitrites) [4]. Taking tadalafil with any of these can cause a dangerous fall in blood pressure. You must also not take tadalafil alongside another PDE5 inhibitor such as sildenafil or vardenafil.

If you take an alpha-blocker for an enlarged prostate (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 or fainting [4]. Similarly, if you take medicines that strongly inhibit the enzyme CYP3A4 (such as ritonavir, ketoconazole, or clarithromycin), your tadalafil dose may need to be adjusted. Loratadine does not fall into any of these high-risk categories, which is why it is generally safe to continue using it.

Declaring All Your Medicines

Always list every medicine you take during your consultation, even if you bought it over the counter or think it is 'just' a vitamin or herbal remedy. Some supplements (such as St John's wort) can reduce the effectiveness of tadalafil, and others may interact in unexpected ways. Being open and thorough helps your prescriber make the safest decision for you.

Practical Advice for Taking Tadalafil and Loratadine Together

If you have been prescribed tadalafil and you also take loratadine for allergies, you can usually take both medicines as directed without concern. There is no need to separate the doses by a specific time, and you do not need to stop your antihistamine while using tadalafil. Simply follow the instructions on each medicine's packaging or as advised by your prescriber and pharmacist.

Take tadalafil on-demand tablets at least 30 minutes before sexual activity, or take daily tadalafil at the same time each day [4]. Loratadine is usually taken once daily, at any time of day, with or without food. If you experience any unexpected side effects—such as severe dizziness, a persistent headache, or an allergic reaction—stop taking the medicines and seek advice from your pharmacist or GP promptly.

Remember that tadalafil requires sexual stimulation to work [1]. It will not cause an erection by itself, and it does not increase sexual desire. Avoid drinking large amounts of alcohol, as this can make erectile dysfunction worse and increase the risk of side effects such as dizziness and low blood pressure [4]. Grapefruit juice can raise tadalafil levels in your blood, so it is best avoided.

When to Seek Medical Advice About Tadalafil and Loratadine

While tadalafil and loratadine are generally safe to take together, there are some situations where you should seek medical advice. If you develop an erection that lasts longer than four hours (priapism), go to A&E immediately, as this is a medical emergency that requires urgent treatment to prevent permanent damage [4]. Similarly, if you experience sudden loss of vision or hearing, chest pain during sex, or severe dizziness or fainting, stop taking tadalafil and seek urgent medical help.

If you start a new medicine (prescribed or over the counter) while taking tadalafil, check with your pharmacist or GP to ensure it is safe to use alongside your ED treatment. This is especially important if you are prescribed antibiotics (such as clarithromycin or erythromycin), antifungals (such as ketoconazole or itraconazole), or medicines for HIV, as these can interact with tadalafil [4].

If your erectile dysfunction is new or has worsened recently, see your GP for a full assessment. ED can be an early warning sign of underlying health problems such as heart disease, high blood pressure, or diabetes [1][2]. Treating the underlying cause can improve your overall health and may also improve your erections. At Cured Pharmacy, our online consultation is designed to identify any red flags and will advise you to see your GP if further investigation is needed.

Reporting Side Effects

If you experience side effects from tadalafil or loratadine, you can report them via the Yellow Card Scheme at yellowcard.mhra.gov.uk or by searching for the MHRA Yellow Card app. Reporting side effects helps improve the safety of medicines for everyone.

Scientific References

1. NHS. (n.d.). Erectile dysfunction (impotence). NHS website. https://www.nhs.uk/conditions/erection-problems-erectile-dysfunction/ [accessed 22 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 22 October 2026]
3. Joint Formulary Committee. (n.d.). Tadalafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/tadalafil/ [accessed 22 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.