Tadalafil and Fluoxetine: Can You Take Them Together?

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What is tadalafil and fluoxetine used for?

Tadalafil (often known by the brand name Cialis) is a prescription medicine used to treat erectile dysfunction 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 available as an on-demand treatment (10mg or 20mg taken at least 30 minutes before sex, with effects lasting up to 36 hours) or as a daily low-dose tablet (2.5mg or 5mg) [4].

Fluoxetine (commonly known by the brand name Prozac) is a selective serotonin reuptake inhibitor (SSRI) antidepressant. It is prescribed for depression, obsessive-compulsive disorder (OCD), bulimia nervosa, and some anxiety disorders. Fluoxetine works by increasing levels of serotonin, a chemical messenger in the brain that helps regulate mood. It is usually taken once daily and can take several weeks to show its full effect.

Both medicines are prescription-only in the UK. If you are taking fluoxetine and are considering treatment for erectile dysfunction, a prescriber will review your full medication list and medical history to ensure tadalafil is suitable and safe for you.

Can you take tadalafil and fluoxetine together?

Yes, tadalafil and fluoxetine can generally be taken together. There is no major direct drug interaction between these two medicines, and they are commonly prescribed at the same time [3][4]. Neither medicine significantly affects the way the other is broken down or works in the body, so the combination is usually considered safe when prescribed appropriately.

However, it is important to understand that fluoxetine itself can sometimes contribute to sexual side effects, including erectile dysfunction or delayed ejaculation, in some men. This is a known side effect of SSRI antidepressants. If you have noticed changes in your sexual function since starting fluoxetine, it is worth discussing this with your GP, as they may be able to adjust your dose or consider an alternative antidepressant.

Your prescriber will still need to check your full medical history, blood pressure, and all current medicines during the consultation. Even though tadalafil and fluoxetine do not interact directly, other factors—such as your heart health, other medicines you take, and any underlying conditions—must be assessed to ensure tadalafil is safe for you [2].

Why your prescriber needs to know about all your medicines

When you request tadalafil, you must declare every medicine you take, including fluoxetine and any over-the-counter or herbal products. This is because tadalafil has serious interactions with certain other medicines—particularly nitrates (such as GTN spray or isosorbide mononitrate), nicorandil, riociguat, and recreational drugs called poppers (amyl or alkyl nitrites). Taking tadalafil with any of these can cause a dangerous drop in blood pressure and must be avoided [3][4].

Your prescriber will also check for medicines that can raise tadalafil levels in your blood (such as some antifungals, antibiotics, or HIV medicines) or lower blood pressure further (such as alpha-blockers or other blood-pressure tablets). Even if fluoxetine itself is not a problem, the full picture of your health and medication is essential for safe prescribing.

How tadalafil and fluoxetine work in the body

Tadalafil works by blocking an enzyme called phosphodiesterase type 5 (PDE5). Normally, PDE5 breaks down a substance called cyclic GMP, which helps relax smooth muscle and widen blood vessels in the penis. By blocking PDE5, tadalafil allows cyclic GMP to build up, improving blood flow to the penis during sexual arousal and making it easier to get and keep an erection [4]. Tadalafil does not cause an erection on its own—you still need sexual stimulation for it to work.

Fluoxetine works in a completely different way. It blocks the reuptake (reabsorption) of serotonin in the brain, which means more serotonin is available to pass messages between nerve cells. This helps improve mood and reduce symptoms of depression and anxiety. Fluoxetine is broken down mainly by liver enzymes, but it does not significantly affect the enzymes that break down tadalafil, which is why the two medicines can usually be taken together without dose adjustment [12].

Because the two medicines act on different systems in the body, they do not interfere with each other's main effects. However, both can have an impact on blood pressure (tadalafil can lower it slightly, and fluoxetine rarely affects it), so your prescriber will check that your blood pressure is stable before prescribing tadalafil.

What you need to know

• Tadalafil and fluoxetine can usually be taken together with no major direct interaction
• Your prescriber will check your full medical history and all current medicines before prescribing
• Fluoxetine itself can sometimes cause sexual side effects in some men
• Never take tadalafil with nitrates, nicorandil, riociguat, or poppers
• See your GP if you have new erectile dysfunction, as it can signal underlying health problems

What your prescriber checks before prescribing tadalafil and fluoxetine

Before prescribing tadalafil to someone taking fluoxetine, a UK prescriber will review your full medical history and current medicines. They will check that you do not have any 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) [2][4].

Your prescriber will also confirm that you are not taking any medicines that interact dangerously with tadalafil. This includes nitrates (used for angina), nicorandil, riociguat (for pulmonary hypertension), or another PDE5 inhibitor. If you take an alpha-blocker (such as tamsulosin or doxazosin) for prostate symptoms or high blood pressure, you must be stable on that medicine and will usually start on the lowest dose of tadalafil, as the combination can cause dizziness or low blood pressure [3][4].

The prescriber will ask about your cardiovascular health, as sexual activity itself can put strain on the heart. If you have significant heart disease or your doctor has advised you to avoid strenuous activity, tadalafil may not be suitable [2]. They will also check for any other medicines that might raise tadalafil levels (such as certain antifungals or HIV medicines) or lower your blood pressure further.

Starting tadalafil while on fluoxetine

If you are already taking fluoxetine and your prescriber decides tadalafil is suitable, you will usually start on a standard dose—either 10mg on-demand or, if you prefer, a daily 2.5mg or 5mg dose [4]. There is no need to adjust the dose of tadalafil simply because you take fluoxetine, as the two medicines do not significantly affect each other's levels in the blood.

Your prescriber may advise you to take the first dose at a time when you can monitor how you feel, especially if you also take other medicines that can lower blood pressure. If you experience dizziness, light-headedness, or any other side effects, contact your prescriber or pharmacist for advice. Do not stop taking fluoxetine or change its dose without speaking to your GP, as stopping an antidepressant suddenly can cause withdrawal symptoms.

Practical advice for taking tadalafil and fluoxetine together

If you have been prescribed both tadalafil and fluoxetine, take each medicine exactly as directed. Fluoxetine is usually taken once a day, at the same time each day, with or without food. Tadalafil on-demand tablets (10mg or 20mg) should be taken at least 30 minutes before you plan to have sex, and the effect can last 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.

You can take tadalafil and fluoxetine at different times of the day if that suits your routine—there is no need to separate them by a specific number of hours. Swallow tadalafil tablets whole with water; they can be taken with or without food. Avoid drinking large amounts of alcohol when taking tadalafil, as alcohol can make erectile dysfunction worse and increase the risk of side effects such as dizziness or low blood pressure [3][4].

If you notice any new symptoms after starting tadalafil—such as persistent headache, flushing, indigestion, back pain, or muscle aches—these are common side effects and usually mild. However, if you experience chest pain during sex, an erection lasting more than four hours (priapism), or sudden loss of vision or hearing, stop taking tadalafil and seek urgent medical help [4]. Always tell any healthcare professional you see (including your dentist or a hospital doctor) that you are taking both tadalafil and fluoxetine.

When to get urgent help

• Erection lasting more than 4 hours (priapism) – go to A&E immediately
• Sudden loss of vision or hearing – stop tadalafil and seek urgent medical help
• Chest pain during or after sex – call 999 and do not take more tadalafil
• Severe dizziness or fainting – stop tadalafil and contact your GP or call 111

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

When to speak to your GP about tadalafil and fluoxetine

If you have recently developed erectile dysfunction, it is important to see your GP for a full assessment, even if you are already taking fluoxetine. Erectile dysfunction can be an early warning sign of underlying health problems such as heart disease, diabetes, or high blood pressure, and treating these conditions can improve your overall health and sexual function [1][2].

If you think fluoxetine may be contributing to your erectile difficulties, discuss this with your GP. They may be able to adjust your dose, switch you to a different antidepressant, or suggest other strategies. Do not stop taking fluoxetine suddenly without medical advice, as this can cause withdrawal symptoms and a return of depression or anxiety.

You should also speak to your GP if tadalafil does not work for you, if you experience troublesome side effects, or if your erectile dysfunction worsens. Your GP can review your treatment, check for other causes, and refer you to a specialist if needed. If you develop any new medical conditions or are prescribed new medicines while taking tadalafil and fluoxetine, let your prescriber know so they can check that everything remains safe and suitable for you [2].

Getting tadalafil through Cured Pharmacy

Cured Pharmacy is a GPhC-registered online pharmacy offering a confidential consultation service for erectile dysfunction treatment. After you complete an online health questionnaire, a UK-registered prescriber will review your answers, including all your current medicines such as fluoxetine, 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 ED treatments, including generic tadalafil from £7.95 and branded Cialis from £12.00 (first order with code Ednew: £6.36 and £9.60 respectively). All prices include the consultation, prescription, and delivery. Our service is designed to be convenient and supportive, but we always encourage you to see your GP if you have new or worsening erectile dysfunction, as a face-to-face assessment can identify important underlying health issues.

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