Tadalafil and Clozapine: Can They Be Taken Together?

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Key takeaways

• No major direct interaction between tadalafil and clozapine is commonly reported, but both can affect blood pressure.
• Your prescriber will review your heart health and all medicines before approving tadalafil.
• Start on the lowest tadalafil dose and watch for dizziness or light-headedness.
• Never take tadalafil with nitrates, nicorandil, riociguat, or poppers.
• Keep your GP, psychiatrist, and pharmacist informed about all your treatments.

What is tadalafil and clozapine used for?

Tadalafil is a phosphodiesterase type 5 (PDE5) inhibitor licensed in the UK to treat erectile dysfunction (ED) [4]. It works by relaxing blood vessels in the penis, allowing increased blood flow when you are sexually aroused. Tadalafil is available as an on-demand treatment (10 mg or 20 mg taken at least 30 minutes before sex, with effects lasting up to 36 hours) or as a daily low-dose tablet (2.5 mg or 5 mg) [4]. It requires sexual stimulation to work and does not cause an automatic erection.

Clozapine is an atypical antipsychotic medicine used to treat schizophrenia, particularly in people who have not responded to other antipsychotic treatments [12]. It works by affecting several brain chemicals, including dopamine and serotonin, to help manage symptoms such as hallucinations, delusions, and disordered thinking. Clozapine requires regular blood monitoring because it can affect white blood cell counts and carries a risk of serious side effects including heart problems and metabolic changes [12].

Both medicines are prescription-only and must be used under medical supervision. If you are taking clozapine and experiencing erectile dysfunction, it is important to discuss this with your GP or psychiatrist, as ED can sometimes be a side effect of antipsychotic medication or related to the underlying condition [1][2].

How do tadalafil and clozapine interact?

There is no well-documented direct pharmacological interaction between tadalafil and clozapine that would make the combination absolutely contraindicated [3][4]. However, both medicines can affect your cardiovascular system in ways that require careful consideration. Tadalafil lowers blood pressure slightly by dilating blood vessels, which is how it helps achieve an erection [4]. Clozapine can also cause low blood pressure (hypotension), particularly when standing up (orthostatic hypotension), and may affect heart rhythm [12].

When these blood-pressure-lowering effects are combined, there is a theoretical risk of dizziness, light-headedness, or fainting, especially when you first start tadalafil or if your clozapine dose has recently changed [2][4]. Clozapine is also associated with an increased risk of heart problems, including cardiomyopathy and myocarditis, so your prescriber will want to ensure your heart is healthy enough for sexual activity before approving any ED treatment [2][12].

Additionally, clozapine can cause metabolic side effects such as weight gain and diabetes, which are themselves risk factors for erectile dysfunction [1][2]. Your prescriber will take all of these factors into account during your consultation. It is essential that you declare clozapine (and any other medicines you take) when requesting tadalafil, so the prescriber can make a safe, informed decision.

What will my prescriber check before approving tadalafil?

When you request tadalafil through Cured Pharmacy, a UK-registered prescriber will review your online consultation carefully [2]. They will ask about all your current medicines, including clozapine, the dose you take, and how long you have been on it. They will also ask about your cardiovascular health, including blood pressure, any history of heart disease, chest pain, stroke, or heart rhythm problems [2][4].

Because clozapine is used for a serious mental health condition and requires specialist monitoring, your prescriber may want to confirm that your treatment is stable and that your psychiatrist or GP is aware you are considering ED treatment [12]. They will also check whether you have any conditions that make PDE5 inhibitors unsuitable, such as recent heart attack or stroke, severe heart failure, very low blood pressure, or a history of sudden vision loss [2][4].

If you are taking other medicines that can interact with tadalafil—such as nitrates (GTN spray, isosorbide mononitrate), nicorandil, riociguat, or alpha-blockers (e.g. doxazosin, tamsulosin)—your prescriber will need to assess whether tadalafil is safe or whether an alternative approach is better [3][4]. Never take tadalafil with nitrates, nicorandil, riociguat, or poppers, as this combination can cause a dangerous drop in blood pressure [4].

Starting on the lowest dose

If your prescriber approves tadalafil, they will usually start you on the lowest effective dose to minimise the risk of side effects, particularly dizziness or low blood pressure [4]. For on-demand tadalafil, this is typically 10 mg, which can be adjusted if needed. You should take it at least 30 minutes before sexual activity and no more than once a day [4]. If you experience dizziness, light-headedness, or any chest discomfort, stop and seek medical advice promptly.

Practical advice for using tadalafil and clozapine together

If your prescriber approves tadalafil while you are taking clozapine, there are several practical steps you can take to use it safely. First, take tadalafil exactly as prescribed and do not exceed the recommended dose [4]. Start with the lowest dose and see how you respond before considering any increase. Take it on an empty stomach or after a light meal, as a heavy or high-fat meal can delay its effect [4].

Be mindful of your blood pressure, especially when you stand up. Both clozapine and tadalafil can cause dizziness, so rise slowly from sitting or lying down, particularly in the first few hours after taking tadalafil [4][12]. Avoid drinking large amounts of alcohol, as this can worsen erectile dysfunction, increase the risk of low blood pressure, and make side effects more likely [4].

Do not stop or change your clozapine dose without consulting your psychiatrist, even if you experience side effects from tadalafil. If you think clozapine itself may be contributing to your erectile dysfunction, discuss this with your doctor—they may be able to adjust your treatment or suggest other strategies [1][2]. Keep all your healthcare professionals informed: your GP, psychiatrist, and pharmacist should all know you are using tadalafil.

When to seek help

Seek urgent medical help if you experience an erection lasting more than four hours (priapism), sudden loss of vision or hearing, or chest pain during sexual activity [4]. If you feel very dizzy, faint, or unwell after taking tadalafil, stop and contact your GP or NHS 111 for advice. Any new or worsening heart symptoms, such as palpitations or breathlessness, should be reported to your doctor promptly, as clozapine can affect the heart [12].

Are there alternatives to tadalafil if I take clozapine?

If tadalafil is not suitable or if you experience troublesome side effects, there are other licensed ED treatments available in the UK [1][2]. Sildenafil (generic Viagra) is another PDE5 inhibitor that works in a similar way but has a shorter duration of action—about four to six hours [3]. Vardenafil (generic Levitra) and avanafil (Spedra) are also PDE5 inhibitors with slightly different profiles [5][6]. All of these medicines have similar considerations regarding blood pressure and cardiovascular health, so the same precautions apply [2].

If oral PDE5 inhibitors are not appropriate, your GP may discuss other options such as vacuum erection devices, alprostadil cream (Vitaros), or alprostadil injections (Caverject) [7]. These treatments work differently and may be suitable in some cases where tablets are not [2][7]. Psychological support, such as cognitive behavioural therapy or psychosexual counselling, can also be helpful, especially if anxiety or relationship issues are contributing to ED [1][2].

It is important to see your GP if you are experiencing new or worsening erectile dysfunction, as it can be an early warning sign of cardiovascular disease or diabetes [1][2]. Your GP can also review whether any of your medicines, including clozapine, might be contributing to the problem and whether any adjustments are possible.

How Cured Pharmacy can help with tadalafil and clozapine

Cured Pharmacy is a GPhC-registered online pharmacy (GPhC 9012511) offering a convenient, confidential way to access erectile dysfunction treatment after a clinical consultation with a UK-registered prescriber [2]. When you complete your online consultation, you will be asked to list all your current medicines, including clozapine, and to provide details about your medical history. A prescriber will review your answers carefully and approve treatment only if it is safe and appropriate for you [2].

We offer a range of ED treatments, including generic and branded tadalafil, as well as sildenafil, vardenafil, and avanafil. Tadalafil (generic Cialis) is available from £7.95, or £6.36 for your first order with code Ednew. Sildenafil (generic Viagra) starts at £0.45 per tablet (£0.36 with code Ednew). All medicines are dispensed by our UK pharmacists and delivered discreetly to your door.

If you have any questions about using tadalafil with clozapine, our pharmacy team is here to help. You can contact us through the website or speak to a pharmacist for advice. Remember, never stop or change your clozapine without consulting your psychiatrist, and always declare all your medicines during your ED consultation to ensure safe, effective treatment.

Getting started

To request tadalafil, complete a short online consultation on our website. Be honest and thorough when listing your medicines and medical history—this helps the prescriber make the safest decision for you [2]. If approved, your treatment will be dispensed and dispatched quickly, usually within 24 hours. If the prescriber has any concerns, they may ask for more information or suggest an alternative approach.

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 or go to A&E
• Severe dizziness, fainting, or feeling very unwell—contact your GP or NHS 111 urgently
• New or worsening heart symptoms (palpitations, breathlessness)—speak to your doctor the same day

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

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