Tadalafil and Co-Amoxiclav: Can You Take Them Together?

Tadalafil and Co-Amoxiclav: Understanding the Interaction

Published: 19 October 2026

Many men wonder whether tadalafil and co-amoxiclav can be taken together safely. The good news is that no major interaction is commonly reported between tadalafil (Cialis) and co-amoxiclav, a widely prescribed antibiotic. However, every medicine you take must be declared during your consultation so that your prescriber or pharmacist can check your full medication list and ensure the combination is appropriate for you.

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 blood vessels in the penis, allowing increased blood flow when you are sexually aroused. Tadalafil is the generic name for Cialis and is available in two forms: on-demand tablets (10mg or 20mg taken at least 30 minutes before sex, with effects lasting up to 36 hours) and daily tablets (2.5mg or 5mg taken once a day) [4].

Tadalafil does not cause an erection on its own—sexual stimulation is still needed [4]. It is one of the most popular ED treatments because of its long duration of action, often called the 'weekend pill'. At Cured Pharmacy, tadalafil is available after a short online consultation reviewed by a UK-registered prescriber. Common side effects include headache, indigestion, back pain, and flushing, which are usually mild and temporary [4].

What Is Co-Amoxiclav and When Is It Prescribed?

Co-amoxiclav is a commonly prescribed antibiotic that combines two active ingredients: amoxicillin (a penicillin antibiotic) and clavulanic acid (which helps the antibiotic work more effectively). It is used to treat a wide range of bacterial infections, including chest infections, urinary tract infections, skin infections, dental abscesses, and ear infections. Co-amoxiclav is usually prescribed for short courses, typically 5 to 7 days, depending on the type and severity of the infection.

Like all antibiotics, co-amoxiclav should be taken exactly as prescribed, even if you start to feel better before finishing the course. This helps prevent antibiotic resistance. Common side effects include diarrhoea, nausea, and skin rashes. Co-amoxiclav does not directly affect erectile function, but feeling unwell with an infection can temporarily reduce libido and sexual performance. Once the infection clears, these effects usually resolve.

Does Co-Amoxiclav Affect Erectile Function?

Co-amoxiclav itself does not cause erectile dysfunction. However, being unwell with a bacterial infection can temporarily affect your interest in sex and your ability to get or maintain an erection. Fatigue, discomfort, and general illness can all reduce libido. These effects are usually short-lived and improve once the infection is treated and you recover. If you notice persistent erectile difficulties after finishing a course of antibiotics, it is worth discussing with your GP, as ED can sometimes signal underlying health conditions such as diabetes or cardiovascular disease [1].

Can You Take Tadalafil and Co-Amoxiclav Together?

No major interaction is commonly reported between tadalafil and co-amoxiclav. This means that, in general, these two medicines can be taken together without one significantly affecting how the other works. Co-amoxiclav is not known to increase or decrease the levels of tadalafil in your body, and tadalafil does not interfere with the antibiotic action of co-amoxiclav. However, it is essential that you declare all medicines you are taking—including antibiotics—during your consultation, so your prescriber or pharmacist can review your full medication list and medical history.

While the combination is not typically problematic, individual circumstances vary. Your prescriber will check for any other medicines or health conditions that might affect the safety of tadalafil. For example, if you are taking other medicines that interact with tadalafil (such as nitrates, alpha-blockers, or certain antifungals), these must be identified and managed [4]. Always be honest and thorough when listing your current medicines, including over-the-counter products, herbal supplements, and any recreational substances.

What Your Prescriber Will Check

During your online consultation at Cured Pharmacy, the prescriber will review your full medical history and current medication list. They will check for any contraindications to tadalafil, such as use of nitrates (GTN spray, isosorbide mononitrate), nicorandil, riociguat, or recreational drugs known as 'poppers' (amyl or alkyl nitrites)—all of which must never be taken with tadalafil due to the risk of a dangerous drop in blood pressure [4]. They will also assess whether you have conditions that make sexual activity inadvisable, such as recent heart attack or stroke, unstable angina, or severe heart failure [4]. If you are taking alpha-blockers (e.g. tamsulosin, doxazosin) or potent CYP3A4 inhibitors (e.g. ritonavir, ketoconazole, clarithromycin), dose adjustments or additional precautions may be needed [4].

Tadalafil and Co-Amoxiclav: Practical Advice for Safe Use

If you have been prescribed co-amoxiclav for an infection and you are already taking tadalafil, or you wish to use tadalafil while on antibiotics, here is some practical guidance. First, take each medicine exactly as prescribed: co-amoxiclav is usually taken two or three times a day with food to reduce stomach upset, while tadalafil on-demand tablets are taken at least 30 minutes before sexual activity (or once daily if you are using the daily dose). There is no need to separate the doses of these two medicines, as they do not interfere with each other's absorption.

Remember that feeling unwell with an infection may temporarily reduce your interest in sex or your ability to achieve an erection—this is normal and not a sign that tadalafil has stopped working. Stay well hydrated, especially if you experience diarrhoea (a common side effect of co-amoxiclav), and avoid heavy alcohol, which can worsen both ED and antibiotic side effects. If you develop any new symptoms—such as severe dizziness, chest pain, prolonged erection lasting more than 4 hours, or sudden vision or hearing loss—seek urgent medical help. Always inform any healthcare professional treating you (including your GP, dentist, or hospital doctor) that you are taking tadalafil.

Other Medicines That Can Interact with Tadalafil

While tadalafil and co-amoxiclav do not interact significantly, tadalafil does have important interactions with other medicines that you must be aware of. Never take tadalafil with nitrates (such as GTN spray, isosorbide mononitrate or dinitrate), nicorandil, riociguat, or recreational drugs called 'poppers' (amyl or alkyl nitrites), as the combination can cause a dangerous fall in blood pressure [4]. If you take alpha-blockers for prostate symptoms or high blood pressure (e.g. tamsulosin, doxazosin, alfuzosin), you should be stable on the alpha-blocker before starting tadalafil, and your prescriber will usually recommend the lowest dose of tadalafil to minimise the risk of dizziness or fainting [4].

Potent CYP3A4 inhibitors—including some antifungals (ketoconazole, itraconazole), certain antibiotics (clarithromycin, erythromycin), and HIV medicines (ritonavir, cobicistat, or Paxlovid)—can increase tadalafil levels in your blood, requiring dose adjustments [4]. Conversely, CYP3A4 inducers such as rifampicin, carbamazepine, phenytoin, and St John's wort can reduce tadalafil's effectiveness. Grapefruit juice may also raise tadalafil levels and should be avoided. Other blood-pressure-lowering medicines can add to the blood-pressure effect of tadalafil, causing dizziness, but this is usually manageable with careful prescribing [4]. Always declare every medicine, supplement, and herbal product you use during your consultation.

When to Avoid Tadalafil

Tadalafil is not suitable for everyone. Do not use tadalafil if you take nitrates, nicorandil, riociguat, or another PDE5 inhibitor, or if you use 'poppers' [4]. It is also not recommended if you have very low blood pressure, a recent history of heart attack or stroke, unstable angina, severe heart failure, or if sexual activity is inadvisable for cardiovascular reasons [4]. Men with a history of non-arteritic anterior ischaemic optic neuropathy (NAION, a form of sudden vision loss) or certain inherited retinal disorders should not use tadalafil [4]. If you have severe liver or kidney problems, dose adjustments or alternative treatments may be needed. Your prescriber will assess your suitability during the consultation.

Getting Tadalafil Safely from Cured Pharmacy

At Cured Pharmacy, a GPhC-registered online pharmacy (GPhC 9012511), you can request tadalafil after completing a short online consultation. A UK-registered prescriber will review your answers, medical history, and current medicines—including any antibiotics such as co-amoxiclav—to ensure tadalafil is safe and appropriate for you. If approved, your medicine is dispensed by our pharmacy team and delivered discreetly to your door. We offer a range of tadalafil options, including generic tadalafil and branded Cialis, with prices starting from £7.95 (or £6.36 for first orders with code Ednew).

Erectile dysfunction is very common, affecting around half of men aged 40–70 to some degree [1]. It can be an early warning sign of conditions like diabetes or heart disease, so if you are experiencing ED for the first time, we encourage you to see your GP for a full health check [1][2]. Tadalafil and other PDE5 inhibitors are effective treatments that can help many men regain confidence and enjoy a fulfilling sex life, but they work best as part of a holistic approach that includes healthy lifestyle choices, management of underlying conditions, and open communication with your partner and healthcare team [2].

Scientific References

1. NHS. (n.d.). Erectile dysfunction (impotence). NHS website. https://www.nhs.uk/conditions/erection-problems-erectile-dysfunction/ [accessed 19 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 19 October 2026]
3. Joint Formulary Committee. (n.d.). Tadalafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/tadalafil/ [accessed 19 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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