Tadalafil and Sulfasalazine: Can You Take Them Together?

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Tadalafil and Sulfasalazine: Understanding the Interaction

Published: 26 October 2026

Many men wonder whether tadalafil and sulfasalazine can be taken together safely. The good news is that no major interaction between these two medicines is commonly reported in clinical practice. However, every person's situation is unique, and your prescriber will review all your current medicines—including sulfasalazine—during your consultation to ensure tadalafil is suitable and safe for you.

What is tadalafil and sulfasalazine used for?

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 active ingredient in Cialis and is available in on-demand doses (10mg or 20mg, taken at least 30 minutes before sex, with effects lasting up to 36 hours) or as a daily low dose (2.5mg or 5mg) [4].

Sulfasalazine is a disease-modifying anti-rheumatic drug (DMARD) used to treat inflammatory conditions such as rheumatoid arthritis, ulcerative colitis, and Crohn's disease. It works by reducing inflammation in the body. Sulfasalazine is taken regularly, usually twice daily, and is not related to sexual function or blood pressure control.

Because these medicines work in completely different ways and target different systems in the body, they do not typically interfere with each other's action. However, it is essential that your prescriber knows about all your medicines, including sulfasalazine, to check for any individual factors that might affect your treatment.

Is there an interaction between tadalafil and sulfasalazine?

No significant interaction between tadalafil and sulfasalazine is commonly reported in standard drug interaction databases or clinical practice. Sulfasalazine does not affect the enzyme systems (such as CYP3A4) that break down tadalafil in the body, and tadalafil does not interfere with how sulfasalazine works to reduce inflammation.

However, it is important to understand that 'no commonly reported interaction' does not mean the combination is automatically suitable for everyone. Your overall health, other medicines you take, and the underlying conditions being treated all play a role in whether tadalafil is safe for you. For example, some inflammatory conditions can be associated with cardiovascular risk factors, which your prescriber will assess.

During your online consultation at Cured Pharmacy, the UK-registered prescriber will review your full medical history and current medicines—including sulfasalazine—to ensure tadalafil is appropriate. You should never stop or change your sulfasalazine without advice from the doctor who prescribed it, even if you start ED treatment.

What your prescriber checks

When you request tadalafil, the prescriber will ask about all your current medicines, including sulfasalazine, to check for any interactions or contraindications. They will also review your cardiovascular health, blood pressure, and whether you take any medicines that must not be combined with tadalafil—such as nitrates, nicorandil, or riociguat [4]. If you are on other blood-pressure-lowering medicines or alpha-blockers, the prescriber will ensure you start on the lowest suitable dose of tadalafil to minimise the risk of dizziness or low blood pressure.

How does tadalafil work, and what affects it?

Tadalafil works by blocking an enzyme called phosphodiesterase type 5 (PDE5) in the smooth muscle of blood vessels in the penis [4]. When you are sexually aroused, your body releases nitric oxide, which triggers a chain reaction that relaxes these blood vessels and increases blood flow. PDE5 normally breaks down the chemical messenger (cGMP) responsible for this relaxation. By inhibiting PDE5, tadalafil allows cGMP to build up, sustaining the erection.

Sexual stimulation is essential—tadalafil will not cause an erection on its own. The medicine is broken down mainly by an enzyme in the liver called CYP3A4. Medicines that strongly inhibit this enzyme (such as ritonavir, ketoconazole, itraconazole, or clarithromycin) can raise tadalafil levels in the blood, requiring dose adjustments [4]. Conversely, medicines that speed up CYP3A4 (such as rifampicin, carbamazepine, phenytoin, or St John's wort) can reduce tadalafil's effectiveness.

Sulfasalazine does not significantly affect CYP3A4, so it is not expected to alter how your body processes tadalafil. Grapefruit juice, however, can raise tadalafil levels and should be avoided or limited. Heavy alcohol can worsen erectile dysfunction and add to the blood-pressure-lowering effect of tadalafil, so moderation is advised [1].

Can sulfasalazine cause erectile dysfunction?

Sulfasalazine itself has been associated with temporary effects on male fertility, particularly reduced sperm count and motility, which are usually reversible when the medicine is stopped. However, sulfasalazine is not commonly listed as a direct cause of erectile dysfunction in the way that some blood-pressure medicines or antidepressants can be.

That said, the inflammatory conditions sulfasalazine treats—such as rheumatoid arthritis or inflammatory bowel disease—can themselves be associated with fatigue, pain, and reduced quality of life, all of which may indirectly affect sexual function and libido. Chronic inflammation and the stress of managing a long-term condition can also contribute to ED [1].

If you have noticed changes in your erections since starting sulfasalazine, it is worth discussing this with your GP. They can review whether the medicine might be playing a role and whether any adjustments are appropriate. In many cases, treating ED with a medicine like tadalafil can be effective regardless of the underlying cause, provided there are no contraindications.

When to see your GP

New or worsening erectile dysfunction should always be discussed with your GP, as it can be an early warning sign of cardiovascular disease or diabetes [1][2]. Your doctor can check for underlying causes, review all your medicines (including sulfasalazine), and refer you for specialist advice if needed. If tadalafil is suitable, your GP can prescribe it, or you can request it through a regulated online pharmacy like Cured Pharmacy after a clinical consultation.

What are the risks of taking tadalafil and sulfasalazine together?

Because no major interaction is commonly reported between tadalafil and sulfasalazine, the risks of taking them together are generally low for most people. The main considerations are the same as for anyone taking tadalafil: ensuring you do not have contraindications (such as taking nitrates, nicorandil, or riociguat), that your cardiovascular health is suitable for sexual activity, and that any other medicines you take are compatible [4].

Tadalafil can cause side effects such as headache, indigestion, back pain, muscle aches, flushing, or nasal congestion. These are usually mild and temporary. Rarely, tadalafil can cause a sudden drop in blood pressure, especially if combined with other blood-pressure-lowering medicines or alpha-blockers. If you feel dizzy or faint after taking tadalafil, sit or lie down and seek medical advice if symptoms persist.

Sulfasalazine has its own side effects, including nausea, headache, and (rarely) blood disorders or liver problems. There is no evidence that tadalafil worsens these side effects or vice versa. However, if you experience any new or unusual symptoms after starting tadalafil, contact your prescriber or GP. Always report all your current medicines during your consultation so the prescriber can give you personalised advice.

Practical advice for taking tadalafil and sulfasalazine

If your prescriber confirms that tadalafil is suitable for you, you can take it alongside sulfasalazine without any special timing requirements. Sulfasalazine is usually taken twice daily with food, and you should continue this routine as prescribed. Tadalafil on-demand (10mg or 20mg) is taken at least 30 minutes before sexual activity, with effects lasting up to 36 hours [4]. Daily tadalafil (2.5mg or 5mg) is taken once a day at the same time, regardless of when you plan to have sex.

Do not take more than one dose of tadalafil in 24 hours, and never combine it with another PDE5 inhibitor (such as sildenafil or vardenafil) or with nitrates, nicorandil, riociguat, or poppers—these combinations can cause a dangerous drop in blood pressure [4]. If you are prescribed a new medicine by another doctor, always tell them you are taking tadalafil.

Store both medicines as directed on the packaging, keep them out of reach of children, and do not share your tadalafil with anyone else. If you have any questions about your treatment, the pharmacist team at Cured Pharmacy is available to help. Prescription ED medicines are only supplied after an online consultation reviewed by a UK-registered prescriber, ensuring your safety and suitability for treatment.

When to seek urgent help

Seek immediate medical help (call 999 or go to A&E) if you experience an erection lasting more than four hours (priapism), sudden loss of vision or hearing, or chest pain during sex. Priapism is a medical emergency that requires urgent treatment to prevent permanent damage. If you feel unwell or experience severe side effects after taking tadalafil, contact NHS 111 or your GP for advice.

Scientific References

1. NHS. (n.d.). Erectile dysfunction (impotence). NHS website. https://www.nhs.uk/conditions/erection-problems-erectile-dysfunction/ [accessed 26 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 26 October 2026]
3. Joint Formulary Committee. (n.d.). Tadalafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/tadalafil/ [accessed 26 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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