Sildenafil and Mirtazapine: Can They Be Taken Together?

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What is sildenafil and mirtazapine used for?

Sildenafil is a medicine used to treat erectile dysfunction (ED) in men. 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]. Sildenafil is the active ingredient in Viagra and is available in doses of 25mg, 50mg, and 100mg. You take it about one hour before sexual activity, and it works only when you are sexually stimulated.

Mirtazapine is an antidepressant used to treat depression and sometimes anxiety. It works by increasing levels of certain natural chemicals in the brain (noradrenaline and serotonin) that help improve mood and emotional wellbeing. Mirtazapine is usually taken once daily, often at bedtime because it can cause drowsiness. It is not a treatment for erectile dysfunction, but depression itself can contribute to ED, so treating the underlying condition may help improve sexual function over time [1].

How do sildenafil and mirtazapine interact?

There is no major pharmacological interaction between sildenafil and mirtazapine reported in standard drug references [3][12]. This means that mirtazapine does not significantly affect how your body processes sildenafil, and sildenafil does not interfere with the antidepressant action of mirtazapine. The two medicines work through different mechanisms in the body and are not known to directly block or enhance each other's effects.

However, both medicines can cause a small drop in blood pressure. Sildenafil lowers blood pressure as part of its mechanism of action by relaxing blood vessels, and mirtazapine can also cause low blood pressure, particularly when you first start taking it or when standing up quickly (postural hypotension). When taken together, there is a theoretical risk that the blood-pressure-lowering effects could add up, potentially causing dizziness, light-headedness, or fainting in some people. This is why your prescriber will review your medical history, current medications, and blood pressure during your consultation to ensure the combination is safe for you.

The mechanism explained simply

Sildenafil works by blocking an enzyme called PDE5, which allows blood vessels in the penis to stay relaxed and open during sexual arousal. Mirtazapine works in the brain by blocking certain receptors and increasing levels of mood-regulating chemicals. Because they act on different systems, they do not directly interfere with each other. The main consideration is the additive effect on blood pressure, which is usually manageable but must be assessed individually.

When to get urgent help

• Erection lasting longer than 4 hours (priapism) – go to A&E or call 999 immediately
• Sudden loss of vision or hearing – stop sildenafil and seek urgent medical advice
• Chest pain during or after sex – stop activity and seek medical help; do not take nitrates
• Severe dizziness, fainting, or unusually fast heartbeat – sit or lie down and call 111 or your GP
• New or worsening thoughts of self-harm – contact your GP, mental health team, or Samaritans on 116 123

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

What does your prescriber check before prescribing sildenafil and mirtazapine together?

When you request sildenafil through Cured Pharmacy's online consultation, a UK-registered prescriber will review your full medical history and all current medications, including mirtazapine. They will check your blood pressure history, any heart or circulation problems, and whether you have experienced dizziness or fainting. If you are stable on mirtazapine and have no significant cardiovascular issues, sildenafil is usually considered safe to prescribe.

Your prescriber will also ensure you are not taking any medicines that are absolutely contraindicated with sildenafil, such as nitrates (GTN spray, isosorbide mononitrate or dinitrate), nicorandil, riociguat, or recreational drugs known as 'poppers' (amyl or alkyl nitrites). These combinations can cause a dangerous drop in blood pressure and must never be used together [3]. If you take any other blood-pressure medicines, alpha-blockers, or medicines that affect liver enzymes, your prescriber will adjust the dose of sildenafil or advise accordingly.

It is important to declare all your current medicines, including over-the-counter products and supplements, during your consultation. Do not stop or change your mirtazapine or any other prescribed medicine without speaking to your GP or psychiatrist first, as this could affect your mental health.

Practical advice for taking sildenafil with mirtazapine

If your prescriber approves sildenafil, take it exactly as directed. Sildenafil is usually taken about one hour before sexual activity, with or without food, though a heavy or high-fat meal may delay its effect [3]. The usual starting dose is 50mg, but your prescriber may recommend 25mg if you have other medical conditions or take certain other medicines. Do not take sildenafil more than once in 24 hours.

Continue taking your mirtazapine as prescribed by your GP or psychiatrist. Mirtazapine is usually taken once daily, often at bedtime. Do not skip doses or stop taking it because you are using sildenafil; consistent treatment of depression is important for your overall wellbeing and may also improve erectile function over time [1]. If you experience unusual dizziness, light-headedness, or fainting after starting sildenafil, sit or lie down and contact your GP or pharmacist for advice.

Avoid drinking large amounts of alcohol when taking sildenafil, as alcohol can worsen erectile dysfunction and add to the blood-pressure-lowering effect, increasing the risk of dizziness [3]. Grapefruit juice can raise sildenafil levels in your blood and should be avoided. If you have any concerns or side effects, contact your prescriber or pharmacist promptly.

Starting sildenafil while on mirtazapine

If you are already stable on mirtazapine and your mood is well controlled, adding sildenafil is usually straightforward. Your prescriber may start you on a lower dose of sildenafil (25mg) to see how you tolerate it, particularly if you have noticed any dizziness with mirtazapine in the past. You can then increase the dose if needed and if well tolerated.

At a glance

Can mirtazapine cause erectile dysfunction?

Depression itself is a common cause of erectile dysfunction, and treating depression can improve sexual function [1]. However, some antidepressants, particularly SSRIs (selective serotonin reuptake inhibitors) such as sertraline or citalopram, are known to cause sexual side effects including reduced libido and difficulty achieving or maintaining an erection. Mirtazapine is generally considered to have a lower risk of sexual side effects compared to SSRIs, but it can still affect sexual function in some men.

If you have noticed erectile difficulties since starting mirtazapine, it is worth discussing this with your GP. Do not stop taking mirtazapine without medical advice, as stopping antidepressants suddenly can cause withdrawal symptoms and a return of depression. Your GP may be able to adjust your dose, switch you to a different antidepressant with fewer sexual side effects, or support you in using a treatment like sildenafil to manage the ED while continuing your mental health treatment [2].

In many cases, men find that once their depression is well controlled, their sexual function improves. Using sildenafil can provide effective short-term relief from ED while you and your doctor work on the underlying causes, whether they are psychological, related to medication, or a combination of factors.

When to seek urgent help and warning signs with sildenafil and mirtazapine

Sildenafil is generally well tolerated, but you should be aware of certain warning signs that require urgent medical attention. If you develop an erection that lasts longer than four hours (priapism), seek immediate help by attending A&E or calling 999, as this can cause permanent damage to the penis if not treated promptly [3]. Sudden loss of vision in one or both eyes or sudden decrease or loss of hearing (which may be accompanied by ringing in the ears or dizziness) are rare but serious side effects; stop taking sildenafil and seek urgent medical advice.

If you experience chest pain during or after sexual activity, stop and seek medical help. Do not take nitrate medicines (such as GTN spray) if you have used sildenafil in the past 24 hours, as this combination can cause a dangerous drop in blood pressure [3]. If you feel severely dizzy, faint, or have an unusually fast or irregular heartbeat, sit or lie down and contact your GP or call 111 for advice.

Regarding mirtazapine, if you experience new or worsening depression, thoughts of self-harm, or suicidal thoughts, contact your GP or mental health team urgently, or call the Samaritans on 116 123. These symptoms are not related to the interaction with sildenafil but are important to monitor when taking any antidepressant. Always keep your GP informed of all the medicines you are taking so they can provide the best care.

Common side effects to be aware of

Common side effects of sildenafil include headache, flushing, indigestion, and nasal congestion [3]. These are usually mild and temporary. Mirtazapine commonly causes drowsiness, increased appetite, and weight gain. If you experience dizziness or light-headedness when taking both medicines together, this may be due to the additive blood-pressure-lowering effect; stand up slowly from sitting or lying positions and avoid driving or operating machinery if affected. Most men tolerate the combination well, but report any persistent or troublesome side effects to your prescriber.

In summary

• Sildenafil and mirtazapine have no major direct interaction and can usually be taken together safely.
• Both medicines can lower blood pressure, so your prescriber checks your overall health during consultation.
• Do not stop taking mirtazapine without medical advice; sildenafil can be added to your treatment.
• Report dizziness, fainting, or any unusual symptoms to your GP or pharmacist promptly.
• Prescription required after online consultation reviewed by a UK-registered prescriber.

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