Tadalafil and Clindamycin: Can You Take Them Together?

Takes less than 2 minutes to complete 100% online

Tadalafil and Clindamycin: Understanding the Interaction

Published: 19 October 2026

Many men wonder whether tadalafil and clindamycin can be taken together safely. The good news is that no major interaction is commonly reported between tadalafil (a medicine used to treat erectile dysfunction) and clindamycin (an antibiotic). However, every person's situation is different, and your prescriber will review all your current medicines during your consultation to 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. 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 [4]. Tadalafil is the active ingredient in branded Cialis and is also available as a generic medicine.

Tadalafil comes in two main 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 tablets (2.5mg or 5mg) taken once a day at the same time [4]. Unlike some other ED treatments, tadalafil's long duration means you don't need to time it as precisely before sex. However, you still need sexual stimulation for it to work—it won't cause an erection on its own.

Common side effects of tadalafil include headache, indigestion, back pain, muscle aches, flushing, and a blocked or runny nose [4]. These are usually mild and temporary. Tadalafil is not suitable for everyone, particularly men taking nitrates for angina, those with severe heart problems, or men for whom sexual activity is not advisable.

What Is Clindamycin and When Is It Prescribed?

Clindamycin is a prescription antibiotic used to treat a range of bacterial infections, including skin and soft tissue infections, dental infections, bone and joint infections, and some types of pneumonia. It works by stopping bacteria from making the proteins they need to grow and multiply, which helps your immune system clear the infection.

Clindamycin is available in several forms: capsules and oral solution taken by mouth, topical preparations for skin infections (including acne), and intravenous injections for serious infections in hospital. The dose and duration depend on the type and severity of the infection you have. It's important to complete the full course of clindamycin even if you start to feel better, as stopping early can allow the infection to return or contribute to antibiotic resistance.

Like all antibiotics, clindamycin can cause side effects. The most common are diarrhoea, nausea, vomiting, and abdominal pain. A serious but rare side effect is Clostridium difficile-associated diarrhoea (also called C. diff), which causes severe, persistent diarrhoea and requires urgent medical attention. If you develop watery diarrhoea, especially with blood or mucus, contact your GP or call NHS 111 immediately.

How Clindamycin Is Metabolised

Clindamycin is broken down (metabolised) in the liver, but it uses different pathways from tadalafil. Tadalafil is primarily metabolised by an enzyme system called CYP3A4, whereas clindamycin does not significantly interact with this system. This is one reason why the two medicines are not expected to affect each other's levels in the body when taken together.

Can You Take Tadalafil and Clindamycin Together?

No major interaction between tadalafil and clindamycin is commonly reported in clinical practice or drug interaction databases. This means that, for most men, taking these two medicines together is not expected to cause problems. Clindamycin does not significantly affect the way tadalafil is broken down in the body, and tadalafil does not interfere with clindamycin's ability to fight bacterial infections.

However, it's essential to remember that every person's medical history is unique. Your prescriber or pharmacist will review all your current medicines, health conditions, and any allergies during your consultation to make sure the combination is safe for you specifically. Even when no major interaction is expected, individual factors such as kidney or liver function, other medicines you're taking, or underlying health conditions can influence how medicines work in your body.

If you are prescribed clindamycin while you are already taking tadalafil (or vice versa), make sure the prescribing doctor or pharmacist knows about both medicines. Never stop or change a prescribed medicine without advice from a healthcare professional. If you experience any unusual symptoms after starting a new medicine, contact your GP, pharmacist, or call NHS 111 for advice.

What Your Prescriber Checks Before Prescribing Tadalafil

Before prescribing tadalafil, your prescriber will ask about your medical history, current medicines, and any health conditions you have. This is to ensure tadalafil is safe and suitable for you. They will specifically check whether you are taking nitrates (such as GTN spray or isosorbide mononitrate for angina), nicorandil, riociguat, or recreational drugs called 'poppers' (amyl or alkyl nitrites), as tadalafil must never be taken with these medicines—the combination can cause a dangerous drop in blood pressure [4].

Your prescriber will also ask about alpha-blockers (medicines for prostate problems or high blood pressure, such as tamsulosin or doxazosin), as these can interact with tadalafil and increase the risk of dizziness or fainting. If you take an alpha-blocker, you may need to start on a lower dose of tadalafil and be stable on the alpha-blocker first [4]. Medicines that strongly inhibit the enzyme CYP3A4—such as ritonavir, cobicistat, ketoconazole, itraconazole, or clarithromycin—can raise tadalafil levels in the blood, so dose adjustments may be needed.

Your prescriber will also check whether you have any heart problems (such as recent heart attack or stroke, unstable angina, or severe heart failure), very low blood pressure, a history of sudden vision loss (NAION), or inherited retinal disorders, as tadalafil may not be suitable in these situations [4]. They will ask about your current antibiotics, including clindamycin, to ensure there are no concerns with the combination.

Declaring All Your Medicines

It's vital to list every medicine you take during your consultation, including prescription medicines, over-the-counter products, herbal remedies (such as St John's wort), vitamins, and supplements. Even medicines that seem unrelated to ED can sometimes interact with tadalafil or affect your suitability for treatment. Being open and thorough helps your prescriber make the safest decision for you.

Practical Advice for Taking Tadalafil and Clindamycin Safely

If you have been prescribed both tadalafil and clindamycin, take each medicine exactly as directed by your prescriber. Tadalafil on-demand tablets are usually taken at least 30 minutes before sexual activity, while daily tadalafil is taken once a day at the same time [4]. Clindamycin should be taken at evenly spaced intervals throughout the day (for example, every six or eight hours, depending on your dose) to maintain steady levels in your body and fight the infection effectively.

You can take tadalafil and clindamycin at the same time of day or at different times—there is no need to separate the doses. Swallow each medicine with a glass of water, and follow any specific instructions on the label (for example, some forms of clindamycin should be taken with food to reduce stomach upset, while tadalafil can be taken with or without food). Avoid drinking large amounts of alcohol while taking tadalafil, as alcohol can worsen erectile dysfunction and increase the risk of side effects such as dizziness and low blood pressure [4].

Complete the full course of clindamycin even if you start to feel better, as stopping early can allow the infection to return. If you develop severe or persistent diarrhoea while taking clindamycin, contact your GP or call NHS 111 immediately, as this can be a sign of a serious bowel infection. If you experience any side effects from tadalafil—such as a prolonged erection lasting more than four hours, sudden vision or hearing loss, or chest pain during sex—seek urgent medical help.

When to Seek Medical Advice About Tadalafil and Clindamycin

Most men can take tadalafil and clindamycin together without problems, but you should contact a healthcare professional if you experience any concerning symptoms. If you develop severe or bloody diarrhoea, abdominal cramps, or fever while taking clindamycin, this could indicate a serious bowel infection (C. difficile) and requires urgent assessment. Do not take anti-diarrhoea medicines without medical advice, as they can make this condition worse.

For tadalafil, seek immediate medical help (call 999 or go to A&E) if you have an erection that lasts longer than four hours (priapism), sudden loss of vision in one or both eyes, sudden decrease or loss of hearing (which may be accompanied by ringing in the ears or dizziness), or chest pain during or after sex [4]. If you feel dizzy, lightheaded, or faint after taking tadalafil, sit or lie down until you feel better, and contact your GP or pharmacist for advice.

If you are unsure whether a symptom is related to tadalafil, clindamycin, or another cause, don't hesitate to ask for help. Your pharmacist is a valuable resource and can often provide advice quickly. You can also call NHS 111 for guidance at any time. Remember, erectile dysfunction can sometimes be an early warning sign of heart disease or diabetes, so if you have new or worsening ED, see your GP for a full assessment [1].

Ongoing Monitoring and Follow-Up

If you take tadalafil regularly, it's a good idea to have periodic check-ups with your GP to review your overall health, blood pressure, and any other medicines you are taking. If your ED does not improve with tadalafil, or if you develop new symptoms, your doctor can explore other treatment options or investigate underlying causes. Open communication with your healthcare team ensures you get the best and safest care.

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. 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.