Tadalafil and Nitrofurantoin: Can You Take Them Together?

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Key takeaways

• No major interaction is reported between tadalafil and nitrofurantoin, so they can generally be taken together.
• Your prescriber reviews all your medicines during consultation to check for any interactions or safety concerns.
• Always declare every medicine, supplement, and herbal product you take, even if you think it's unrelated.
• Complete your nitrofurantoin course as prescribed, and take tadalafil as directed by your prescriber.
• Seek urgent help if you have chest pain, severe dizziness, or an erection lasting more than four hours.

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 phosphodiesterase type 5 (PDE5) inhibitors, which work by relaxing the blood vessels in the penis, allowing more blood to flow in when you are sexually aroused. This increased blood flow helps you achieve and maintain an erection suitable for sexual activity.

Tadalafil is available as the branded medicine Cialis, or as generic tadalafil from various manufacturers. It can be taken in two ways: on-demand (10 mg or 20 mg taken at least 30 minutes before sexual activity, with effects lasting up to 36 hours) or as a daily low dose (2.5 mg or 5 mg taken once a day) [4]. Unlike some other ED treatments, tadalafil's long duration means you don't need to time it as precisely before sex, which many men find more convenient and spontaneous.

It's important to remember that tadalafil only works when you are sexually stimulated – it does not cause an automatic erection. You still need arousal for the medicine to be effective. Tadalafil is only available on prescription in the UK after a healthcare professional has assessed your suitability, including checking for any interactions with your other medicines and health conditions.

What is nitrofurantoin and when is it prescribed?

Nitrofurantoin is an antibiotic commonly prescribed to treat urinary tract infections (UTIs), including cystitis (bladder infections) and to prevent recurrent UTIs. It works by killing bacteria in the urinary system. Nitrofurantoin is particularly effective against the types of bacteria that most often cause bladder infections, and it concentrates in the urine, making it ideal for treating infections in the urinary tract.

Your GP or prescriber may give you nitrofurantoin as a short course (typically three to seven days) to treat an active infection, or as a longer-term low-dose treatment to prevent infections from coming back. Common brand names include Macrobid and Macrodantin, though generic nitrofurantoin is widely available. The medicine is usually taken as capsules, either twice daily for treatment or once daily at night for prevention.

Like all antibiotics, nitrofurantoin should be taken exactly as prescribed, even if you start to feel better before finishing the course. Stopping early can allow the infection to return and may contribute to antibiotic resistance. Side effects can include nausea, loss of appetite, and discoloured urine (which is harmless), but serious side effects are rare when the medicine is used appropriately.

At a glance

Do tadalafil and nitrofurantoin interact with each other?

Based on current UK prescribing guidance, there is no major interaction reported between tadalafil and nitrofurantoin [4]. This means that, in general, these two medicines can be taken together without one significantly affecting how the other works or causing a dangerous reaction. Nitrofurantoin is not known to interfere with the way tadalafil is broken down in the body, and tadalafil does not affect how nitrofurantoin treats bacterial infections.

However, 'no major interaction' does not mean your prescriber will automatically approve the combination without checking your individual circumstances. During your consultation, the prescriber will review your full medical history, all current medicines (including over-the-counter products and supplements), and any other health conditions. This personalised assessment is essential because everyone's situation is different, and what is safe for one person may not be suitable for another.

It's also worth noting that urinary tract infections themselves can sometimes cause discomfort or pain that might temporarily affect your interest in or ability to have sex. If you're feeling unwell with a UTI, it's perfectly normal to wait until you've recovered before resuming sexual activity. Always complete your antibiotic course as prescribed, and if you have any concerns about taking tadalafil while on nitrofurantoin, discuss them openly with your prescriber or pharmacist.

Why your prescriber still checks every medicine

Even when two medicines don't interact directly with each other, your prescriber must consider the bigger picture. For example, some men taking nitrofurantoin may also be on other medicines for chronic conditions, and it's the combination of all your medicines together that matters. Certain drugs can affect tadalafil levels in your body or increase the risk of side effects like dizziness or low blood pressure, so a thorough review is always necessary before any prescription is issued [4].

What does your prescriber check before approving tadalafil and nitrofurantoin together?

When you request tadalafil through Cured Pharmacy's online consultation, a UK-registered prescriber will review your answers carefully. They will check that you are not taking any medicines that are known to interact dangerously with tadalafil, such as nitrates (GTN spray, isosorbide mononitrate or dinitrate), nicorandil, riociguat, or recreational drugs called 'poppers' (amyl or alkyl nitrites). These combinations can cause a serious drop in blood pressure and must never be used together [3][4].

The prescriber will also look at whether you take alpha-blockers (such as doxazosin, tamsulosin, or alfuzosin) for prostate symptoms or high blood pressure, as these can add to the blood-pressure-lowering effect of tadalafil and cause dizziness. If you are stable on an alpha-blocker, tadalafil can usually still be prescribed, but you may need to start on a lower dose [4]. Medicines that affect how your liver breaks down tadalafil – such as some antifungals (ketoconazole, itraconazole), certain antibiotics (clarithromycin), or HIV medicines (ritonavir, cobicistat) – will also be reviewed, as they can raise tadalafil levels in your blood.

Your prescriber will ask about your heart health, blood pressure, and any history of stroke, as tadalafil is not suitable when sexual activity itself is inadvisable (for example, after a recent heart attack or if you have severe heart failure or very low blood pressure). They will also check for rare conditions like previous sudden vision loss (NAION) or inherited retinal disorders. This thorough assessment ensures that tadalafil is safe and appropriate for you, even when you're taking other medicines like nitrofurantoin.

Declaring all your medicines and supplements

It's essential to list every medicine you take during your consultation, including prescription drugs, over-the-counter products, herbal remedies (such as St John's wort), and supplements. Even if you think something is harmless or unrelated, it could still affect how tadalafil works or increase the risk of side effects. Being thorough and honest helps your prescriber make the safest decision for you.

Practical advice for taking tadalafil and nitrofurantoin safely

If your prescriber approves both medicines, take each one exactly as directed. Nitrofurantoin is usually taken with food or milk to reduce the chance of an upset stomach, and you should complete the full course even if your symptoms improve. Tadalafil on-demand tablets (10 mg or 20 mg) should be taken at least 30 minutes before you plan to have sex, though the effect can last up to 36 hours, giving you flexibility [4]. If you're on daily tadalafil (2.5 mg or 5 mg), take it at the same time each day, regardless of when you plan to be sexually active.

Avoid drinking large amounts of alcohol while taking tadalafil, as heavy drinking can make erectile dysfunction worse and increase the risk of dizziness or low blood pressure. Grapefruit juice can raise tadalafil levels in your blood, so it's best to avoid it or limit your intake. Stay well hydrated while taking nitrofurantoin, as drinking plenty of water helps flush bacteria out of your urinary system and supports the antibiotic's effectiveness.

If you experience any unusual symptoms while taking both medicines – such as severe dizziness, fainting, chest pain, or an erection lasting more than four hours – seek medical help immediately. These are rare but serious side effects that need urgent attention. For less urgent concerns, such as mild headache, indigestion, or back pain (common with tadalafil), or nausea or discoloured urine (common with nitrofurantoin), contact your GP or pharmacist for advice. Never stop a prescribed medicine without professional guidance.

How to access tadalafil through Cured Pharmacy

Cured Pharmacy is a GPhC-registered online pharmacy (GPhC 9012511) offering a convenient, confidential service for erectile dysfunction treatment. To request tadalafil, you'll complete a short online consultation that asks about your health, current medicines (including nitrofurantoin if you're taking it), and any conditions that might affect your suitability for ED treatment. A UK-registered prescriber will review your answers, and if tadalafil is appropriate for you, your medicine will be dispensed by our pharmacy and delivered discreetly to your door.

We stock a range of tadalafil options to suit different needs and budgets. Generic tadalafil starts from £7.95 (or £6.36 for your first order with code Ednew), and we also offer branded Cialis and other ED medicines such as sildenafil (generic Viagra), vardenafil (generic Levitra), and Spedra (avanafil). All our ED medicines are genuine, UK-licensed products, and our service is led by experienced pharmacists who are here to answer your questions and support your treatment safely.

If you're currently taking nitrofurantoin or any other medicine, simply declare it in your consultation. Our prescribers are trained to assess interactions and will only approve tadalafil if it's safe for you. If you have any questions before, during, or after your order, our pharmacy team is available to help. We're committed to making ED treatment accessible, affordable, and straightforward, with the same clinical standards you'd expect from any high-street pharmacy.

Why see a GP for new erectile dysfunction

If you're experiencing erectile dysfunction for the first time, it's important to see your GP for a check-up. ED can be an early warning sign of underlying health conditions such as heart disease, diabetes, or high blood pressure [1][2]. Your GP can arrange tests, discuss lifestyle changes, and refer you to a specialist if needed. Once any underlying causes have been addressed or ruled out, an online service like Cured Pharmacy can provide convenient ongoing access to treatment.

When to get urgent help

• Erection lasting more than 4 hours (priapism) – go to A&E immediately
• Sudden loss of vision or hearing – seek urgent medical attention
• Chest pain during or after sex – call 999 or go to A&E
• Severe dizziness, fainting, or very low blood pressure – seek same-day medical help
• Allergic reaction (swelling of face, lips, tongue, or difficulty breathing) – call 999

Call 999 or go to A&E in an emergency, or contact NHS 111 for urgent advice.

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