Tadalafil and Mirtazapine: Can They Be Taken Together?

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What Is Tadalafil and How Does It Work?

Tadalafil is a prescription medicine used to treat erectile dysfunction (ED). It belongs to a group of medicines called PDE5 inhibitors, which work by relaxing blood vessels in the penis, allowing more blood to flow in when you are sexually aroused [3][4]. Tadalafil is the active ingredient in branded Cialis and is also available as a generic medicine at a lower cost.

Tadalafil comes in two 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, which allow for more spontaneous sexual activity [4]. All PDE5 inhibitors, including tadalafil, require sexual stimulation to work—they do not cause an automatic erection.

Common side effects include headache, indigestion, back pain, muscle aches, flushing, and a blocked or runny nose [4]. These are usually mild and temporary. Tadalafil is only available on prescription in the UK after a clinical assessment by a registered prescriber, who will check whether it is safe and suitable for you.

What Is Mirtazapine and Why Is It Prescribed?

Mirtazapine is an antidepressant medicine used to treat depression and sometimes anxiety. It belongs to a class of medicines called noradrenergic and specific serotonergic antidepressants (NaSSAs). Mirtazapine works by increasing the levels of certain natural chemicals in the brain—noradrenaline and serotonin—which help to improve mood and emotional well-being.

Mirtazapine is usually taken once a day, often at bedtime, because it can cause drowsiness, especially when you first start taking it. Common side effects include increased appetite, weight gain, dry mouth, and feeling sleepy or tired. These effects often settle down after the first few weeks of treatment.

Interestingly, while some antidepressants (particularly SSRIs like sertraline or citalopram) are well known for causing sexual side effects including erectile dysfunction, mirtazapine is less likely to do so. In fact, some men find that switching to mirtazapine from another antidepressant can improve sexual function. However, depression itself is a common cause of ED, so treating the underlying condition is an important part of managing erectile problems [1][2].

Can Depression and Antidepressants Cause ED?

Yes, both depression and some antidepressant medicines can contribute to erectile dysfunction. Depression can reduce libido, energy, and interest in sex, while certain antidepressants—especially SSRIs—can directly affect sexual function [2]. Mirtazapine tends to have a lower risk of sexual side effects compared to SSRIs, but every person responds differently. If you are experiencing ED and take an antidepressant, it is important to discuss this with your GP, who can review your treatment and explore whether a change in medicine or an additional treatment like tadalafil might help.

Can You Take Tadalafil and Mirtazapine Together?

Yes, tadalafil and mirtazapine can generally be taken together. There is no major direct drug interaction between these two medicines that would make the combination unsafe or contraindicated. Many men who take mirtazapine for depression or anxiety are also prescribed tadalafil for erectile dysfunction without problems.

However, your prescriber will still need to check a few important things before confirming that the combination is suitable for you. Mirtazapine can sometimes cause drowsiness, dizziness, and a small drop in blood pressure, particularly when you first start taking it or if the dose is increased. Tadalafil can also lower blood pressure slightly, so taking both medicines together may add to this effect in some people.

During your online consultation at Cured Pharmacy, the prescriber will review your full medical history, current medicines, and any other health conditions to ensure that tadalafil is safe for you. This includes checking for any medicines that do interact dangerously with tadalafil, such as nitrates (GTN spray, isosorbide mononitrate), nicorandil, riociguat, or recreational drugs called poppers—these must never be taken with tadalafil [3][4]. If you are taking mirtazapine and no other contraindicated medicines, and your blood pressure is stable, tadalafil is usually a safe and effective option.

What you need to know

• Tadalafil and mirtazapine can usually be taken together safely with no major direct interaction
• Both medicines can lower blood pressure slightly, so your prescriber checks your history and symptoms
• Mirtazapine is less likely to cause sexual side effects compared to other antidepressants like SSRIs
• Always declare every medicine during your consultation, including mirtazapine and any over-the-counter products
• Never take tadalafil with nitrates, nicorandil, riociguat, poppers, or another PDE5 inhibitor

How the Interaction Between Tadalafil and Mirtazapine Works

Understanding how medicines interact can help you feel more confident about your treatment. Tadalafil works by blocking an enzyme called PDE5, which allows blood vessels in the penis to relax and widen, improving blood flow during sexual arousal [3]. Mirtazapine works on different pathways in the brain, affecting serotonin and noradrenaline receptors to improve mood.

Because these two medicines work on completely different systems in the body, they do not interfere with each other's main actions. Tadalafil is broken down in the liver by enzymes called CYP3A4, and mirtazapine does not significantly affect these enzymes, so it does not change the levels of tadalafil in your blood.

The main consideration is that both medicines can have a mild blood-pressure-lowering effect. Tadalafil relaxes blood vessels throughout the body (not just in the penis), which can cause a small drop in blood pressure. Mirtazapine can also cause dizziness or drowsiness, particularly when you stand up quickly (a condition called postural hypotension). For most people, these effects are mild and manageable, but your prescriber will check your blood pressure history and any symptoms you have experienced to ensure the combination is safe for you.

What Your Prescriber Will Check

Before prescribing tadalafil, your prescriber will ask about your current medicines, including mirtazapine, and any other health conditions. They will check whether you have a history of low blood pressure, dizziness, fainting, or heart problems. They will also ask about any other medicines you take that might interact with tadalafil, such as alpha-blockers (e.g. tamsulosin, doxazosin), other blood pressure medicines, or any of the contraindicated medicines mentioned earlier [3][4]. This careful review ensures that tadalafil is both safe and likely to be effective for you.

Practical Advice for Taking Tadalafil and Mirtazapine Safely

If you are prescribed tadalafil while taking mirtazapine, there are a few simple steps you can take to use both medicines safely and get the best results. First, take each medicine exactly as prescribed. Mirtazapine is usually taken once a day, often at bedtime, while tadalafil on-demand tablets are taken at least 30 minutes before sexual activity (or daily tablets are taken once a day at the same time) [4].

Be aware of how you feel when you stand up, especially in the first few days of taking tadalafil or if your mirtazapine dose has recently changed. If you feel dizzy or light-headed, sit or lie down until the feeling passes, and stand up slowly from sitting or lying positions. Avoid drinking large amounts of alcohol, as this can make dizziness worse and also reduce the effectiveness of tadalafil [3].

If you experience any unusual symptoms—such as severe dizziness, fainting, chest pain during sex, an erection lasting more than four hours, or sudden loss of vision or hearing—seek medical help immediately. These are rare but serious side effects that need urgent attention. Do not stop taking mirtazapine suddenly without speaking to your GP, as this can cause withdrawal symptoms. If you have any concerns about either medicine, contact your prescriber or pharmacist for advice.

When to get urgent help

• An erection lasting more than 4 hours (priapism) – go to A&E immediately
• Sudden loss of vision or hearing – seek urgent medical help
• Chest pain during sexual activity – stop and call 999 if pain does not go away
• Severe dizziness, fainting, or very low blood pressure – contact your GP or call 111
• 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.

Other Medicines and Interactions to Be Aware Of

While tadalafil and mirtazapine can be taken together, it is important to tell your prescriber about every medicine you take, including over-the-counter medicines, herbal remedies, and supplements. Some medicines can interact with tadalafil in ways that are dangerous or reduce its effectiveness [3][4].

Never take tadalafil with nitrates (such as GTN spray, isosorbide mononitrate, or isosorbide dinitrate), nicorandil, riociguat, or recreational drugs called poppers (amyl or alkyl nitrites). This combination can cause a dangerous drop in blood pressure and is absolutely contraindicated [3][4]. Do not take tadalafil with another PDE5 inhibitor (such as sildenafil or vardenafil) at the same time.

If you take alpha-blockers for an enlarged prostate (such as tamsulosin, doxazosin, or alfuzosin), your prescriber will usually start you on a lower dose of tadalafil and ensure you are stable on the alpha-blocker first, as the combination can increase the risk of dizziness and low blood pressure [4]. Some medicines that affect liver enzymes—such as ritonavir, ketoconazole, itraconazole, or clarithromycin—can raise tadalafil levels in your blood, so your prescriber may adjust the dose. Always declare every medicine during your consultation, and never stop or change a prescribed medicine without professional advice.

When to See Your GP

If you are experiencing erectile dysfunction for the first time, it is important to see your GP for a full assessment. 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, review your medicines (including mirtazapine), and discuss treatment options. If you are already under the care of a GP and your ED is well understood, an online consultation with a registered prescriber at Cured Pharmacy can be a convenient way to access treatment.

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