Tadalafil and Azithromycin: Can You Take Them Together?

Tadalafil and Azithromycin: Understanding the Interaction

Published: 18 October 2026

If you've been prescribed both tadalafil and azithromycin, you may wonder whether it's safe to take them together. Tadalafil is a medicine used to treat erectile dysfunction (ED), while azithromycin is a commonly prescribed antibiotic for bacterial infections. The good news is that these two medicines can usually be taken together, but there are important considerations your prescriber will check to ensure your safety.

What is tadalafil and azithromycin used for?

Tadalafil is a phosphodiesterase type 5 (PDE5) inhibitor licensed in the UK to treat erectile dysfunction [4]. It works by relaxing blood vessels in the penis, allowing increased blood flow when you're sexually aroused. Tadalafil is available as on-demand tablets (10mg or 20mg taken at least 30 minutes before sex, with effects lasting up to 36 hours) or as a daily low-dose option (2.5mg or 5mg) [4]. It requires sexual stimulation to work and will not cause an erection on its own.

Azithromycin is a macrolide antibiotic used to treat a range of bacterial infections, including chest infections, skin infections, and some sexually transmitted infections. It works by stopping bacteria from growing and multiplying. Azithromycin is usually taken as a short course – often a single dose or a three-to-five-day treatment. Like all antibiotics, it should only be used when prescribed by a healthcare professional for a confirmed or suspected bacterial infection.

Both medicines are prescription-only in the UK. At Cured Pharmacy, tadalafil is available after an online consultation reviewed by a UK-registered prescriber, ensuring it's safe and suitable for you.

How do tadalafil and azithromycin interact?

Azithromycin is not a potent inhibitor of the liver enzyme (CYP3A4) that breaks down tadalafil, so it does not significantly raise tadalafil levels in the blood. This means that, for most people, taking tadalafil and azithromycin together does not require a dose adjustment of either medicine. No major interaction is commonly reported between these two medicines in standard clinical references [4][12].

However, both medicines can, in rare cases, affect the heart's electrical activity (specifically, they may prolong the QT interval on an ECG). When medicines with this potential are taken together, there is a theoretical risk of an abnormal heart rhythm, particularly in people who already have heart conditions or are taking other medicines that affect the heart. This risk is very small for most people, but it is one reason why your prescriber will ask about your medical history and current medicines during your consultation.

Your prescriber or pharmacist will review your full medication list and health history to ensure the combination is safe for you. If you have a history of heart rhythm problems, low potassium or magnesium levels, or are taking other medicines that affect the QT interval, your healthcare professional may advise extra caution or monitoring.

What happens in your body?

Tadalafil works by blocking an enzyme called PDE5, which normally breaks down a substance (cGMP) that relaxes blood vessels in the penis. By blocking PDE5, tadalafil allows cGMP to build up, improving blood flow and helping you achieve and maintain an erection when sexually aroused [4]. Azithromycin, meanwhile, targets bacterial protein production, stopping infection without directly affecting blood flow or the PDE5 enzyme. Because they work through different pathways, the two medicines do not interfere with each other's primary action.

What your prescriber checks before prescribing tadalafil and azithromycin

When you request tadalafil through Cured Pharmacy's online consultation, a UK-registered prescriber will review your answers to ensure the medicine is safe and appropriate for you. They will ask about all medicines you are currently taking, including antibiotics like azithromycin, as well as over-the-counter products and supplements. This helps identify any potential interactions or contraindications.

Your prescriber 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) [4]. They will also ask about medicines that must never be taken with tadalafil, including nitrates (such as GTN spray or isosorbide mononitrate), nicorandil, riociguat, and recreational drugs known as 'poppers' (amyl or alkyl nitrites). Combining tadalafil with any of these can cause a dangerous drop in blood pressure [4].

If you are taking alpha-blockers (such as tamsulosin or doxazosin) for prostate symptoms or high blood pressure, 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 low blood pressure [4]. They will also review whether you are on any potent CYP3A4 inhibitors (such as ritonavir, ketoconazole, or clarithromycin), which can raise tadalafil levels and require dose adjustments. Azithromycin is not in this category, so it does not require a tadalafil dose change.

Practical advice for taking tadalafil and azithromycin together

If your doctor or prescriber has confirmed it is safe for you to take both medicines, follow the dosing instructions for each one carefully. Take azithromycin exactly as prescribed – usually once a day, with or without food, for the duration of your course (even if you start to feel better). Complete the full course of antibiotics to ensure the infection is fully treated and to reduce the risk of antibiotic resistance.

For tadalafil, take your prescribed dose at least 30 minutes before sexual activity if you are using the on-demand tablets (10mg or 20mg). The effect can last up to 36 hours, so you do not need to take another dose within that time [4]. If you are on daily tadalafil (2.5mg or 5mg), take one tablet at the same time each day, regardless of when you plan to have sex. Remember that tadalafil requires sexual stimulation to work – it will not cause an automatic erection.

Avoid drinking large amounts of alcohol while taking tadalafil, as alcohol can worsen erectile dysfunction and add to the blood-pressure-lowering effect of the medicine, increasing the risk of dizziness or fainting [4]. Grapefruit juice can raise tadalafil levels in the blood, so it is best avoided. If you experience any unusual symptoms – such as dizziness, palpitations, chest pain, or an erection lasting more than four hours – seek medical advice immediately.

Timing your doses

There is no need to separate the timing of tadalafil and azithromycin doses, as they do not interfere with each other's absorption. You can take them at the same time or at different times of day, whichever fits your routine. Just ensure you follow the specific instructions for each medicine – for example, azithromycin is often taken once daily, while on-demand tadalafil is taken only when needed before sexual activity.

Warning signs and when to seek help with tadalafil and azithromycin

Most people tolerate tadalafil and azithromycin well when taken together, but it is important to be aware of warning signs that require urgent medical attention. If you develop an erection that lasts longer than four hours (priapism), seek emergency help immediately, as this can cause permanent damage if not treated promptly [4]. Priapism is rare but is a medical emergency.

Sudden loss of vision in one or both eyes, or sudden decrease or loss of hearing (sometimes with ringing in the ears or dizziness), are rare but serious side effects of PDE5 inhibitors like tadalafil. If you experience either of these symptoms, stop taking tadalafil and seek urgent medical advice [4]. Similarly, if you develop chest pain during or after sexual activity, do not continue – seek medical help straight away, as this may indicate a heart problem.

Azithromycin can occasionally cause allergic reactions, including rash, swelling of the face or throat, or difficulty breathing. If you notice any of these symptoms, stop taking the antibiotic and seek immediate medical help. Severe diarrhoea (especially if it contains blood or mucus) or persistent abdominal pain during or after azithromycin treatment may indicate a serious bowel condition (Clostridioides difficile infection) and requires prompt medical review. If you experience palpitations, fainting, or an unusually fast or irregular heartbeat while taking both medicines, contact your GP or call NHS 111 for advice.

Can I take tadalafil with other antibiotics?

Tadalafil can usually be taken with most antibiotics, but some require extra caution. Clarithromycin, another macrolide antibiotic, is a potent CYP3A4 inhibitor and can significantly raise tadalafil levels in the blood [4]. If you are prescribed clarithromycin, your prescriber may reduce your tadalafil dose or advise you to avoid tadalafil temporarily. Erythromycin, also a macrolide, has a similar but less pronounced effect.

Antibiotics such as amoxicillin, doxycycline, trimethoprim, and nitrofurantoin do not interact significantly with tadalafil and can generally be taken together without dose adjustment. However, it is essential to declare all medicines – including antibiotics – during your consultation, as your prescriber or pharmacist will check each one individually to ensure safety.

Never stop or change a prescribed medicine without consulting your healthcare professional. If you are unsure whether a new antibiotic is safe to take with tadalafil, contact your GP, pharmacist, or the prescriber who issued your tadalafil prescription. At Cured Pharmacy, our team is available to answer questions about your medicines and ensure you receive safe, personalised care.

What about other ED treatments?

The same principles apply to other PDE5 inhibitors used for erectile dysfunction, such as sildenafil (Viagra), vardenafil (Levitra), and avanafil (Spedra). Azithromycin does not significantly interact with these medicines either, but potent CYP3A4 inhibitors (like clarithromycin) can raise their levels and require dose adjustments or avoidance [3][5][6]. Never take two different PDE5 inhibitors together, as this can cause a dangerous drop in blood pressure. If you are considering switching from one ED medicine to another, discuss this with your prescriber first.

Scientific References

1. Joint Formulary Committee. (n.d.). Tadalafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/tadalafil/ [accessed 18 October 2026]
2. Electronic Medicines Compendium. (n.d.). Summaries of Product Characteristics and Patient Information Leaflets. https://www.medicines.org.uk/emc/ [accessed 18 October 2026]
3. Joint Formulary Committee. (n.d.). Sildenafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/sildenafil/ [accessed 18 October 2026]
4. Joint Formulary Committee. (n.d.). Vardenafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/vardenafil/ [accessed 18 October 2026]
5. Joint Formulary Committee. (n.d.). Avanafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/avanafil/ [accessed 18 October 2026]
6. NHS. (n.d.). Erectile dysfunction (impotence). https://www.nhs.uk/conditions/erection-problems-erectile-dysfunction/ 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.

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