Tadalafil and Flecainide: 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 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 generic name for Cialis and is available in two forms: on-demand tablets (10mg or 20mg taken at least 30 minutes before sexual activity, with effects lasting up to 36 hours) and daily low-dose tablets (2.5mg or 5mg taken once a day) [4].

Unlike some other ED treatments, tadalafil has a longer duration of action, which is why it is sometimes called 'the weekend pill'. It only works when you are sexually stimulated and does not cause an automatic erection [1]. Tadalafil is also licensed to treat benign prostatic hyperplasia (an enlarged prostate) and pulmonary arterial hypertension, though at different doses [4].

What is flecainide and why is it prescribed?

Flecainide is a prescription medicine used to treat and prevent abnormal heart rhythms (arrhythmias), particularly atrial fibrillation and other supraventricular arrhythmias. It works by slowing down electrical signals in the heart, helping to restore and maintain a normal, steady heartbeat. Flecainide is usually prescribed by a cardiologist or GP after careful assessment, as it is reserved for people whose heart rhythm problems have not responded to other treatments or where other medicines are unsuitable.

Because flecainide affects the heart's electrical activity, it is important that anyone taking it is monitored regularly. Your doctor will check your heart function with an ECG (electrocardiogram) before starting treatment and at intervals during treatment. Flecainide is not suitable for everyone; it is generally avoided in people with certain types of heart disease, including significant structural heart problems or a history of heart attack [12].

Common side effects of flecainide

Flecainide can cause side effects such as dizziness, visual disturbances (blurred vision or seeing spots), tiredness, and palpitations. Some people may experience nausea or breathlessness. Rarely, flecainide can worsen heart rhythm problems or cause new arrhythmias, which is why close medical supervision is essential. If you experience chest pain, severe dizziness, fainting, or a very fast or irregular heartbeat while taking flecainide, seek urgent medical advice [12].

When to get urgent help

• Chest pain during or after sexual activity—call 999 immediately
• Erection lasting more than 4 hours (priapism)—go to A&E
• Sudden loss of vision or hearing—seek emergency medical help
• Severe dizziness, fainting, or very fast/irregular heartbeat—call 999 or go to A&E
• New or worsening breathlessness or palpitations—contact your GP or call 111 urgently

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

Can you take tadalafil and flecainide together?

Yes, tadalafil and flecainide can generally be taken together, as there is no major direct drug interaction between them reported in standard references [3][4]. Flecainide does not significantly affect the way tadalafil is broken down in the body, and tadalafil does not interfere with flecainide's action on heart rhythm. However, this does not mean the combination is automatically safe for everyone.

Both medicines can affect your cardiovascular system in different ways. Tadalafil can cause a mild drop in blood pressure, and flecainide is used specifically because you have a heart rhythm condition. Your prescriber will need to assess your overall heart health, the severity of your arrhythmia, and whether your heart condition is stable before approving tadalafil [2]. It is essential that you declare all your current medicines, including flecainide, during your online consultation so that the prescriber can make an informed decision about whether ED treatment is suitable and safe for you.

What does your prescriber check before approving tadalafil?

When you request tadalafil treatment and you are taking flecainide, the prescriber will review several important factors. They will ask about the type and severity of your heart rhythm problem, how well controlled it is, and whether you have any other heart conditions such as angina, heart failure, or a history of heart attack or stroke [2]. They will also check whether you take any other medicines that could interact with tadalafil, particularly nitrates, nicorandil, riociguat, alpha-blockers, or other blood pressure medicines.

The prescriber will assess whether sexual activity itself is safe for you. Sexual activity increases the workload on your heart, and if your heart condition is unstable or severe, your doctor may advise that you should not use ED treatment until your condition improves [1][2]. If your flecainide is controlling your arrhythmia well and you have no other significant heart problems, tadalafil may be considered safe at an appropriate dose. The prescriber may recommend starting with a lower dose and monitoring how you respond.

Medicines you must never take with tadalafil

Do not take tadalafil if you use nitrates (such as GTN spray, isosorbide mononitrate, or isosorbide dinitrate), nicorandil, riociguat, or recreational drugs called 'poppers' (amyl or alkyl nitrites). The combination can cause a dangerous, potentially life-threatening drop in blood pressure [4]. You must also not take tadalafil alongside another PDE5 inhibitor (such as sildenafil or vardenafil). Always tell your prescriber about every medicine you take, including over-the-counter products and herbal remedies.

At a glance

Practical advice for taking tadalafil and flecainide safely

If your prescriber approves tadalafil while you are taking flecainide, follow their instructions carefully. Take tadalafil exactly as prescribed—do not take more than the recommended dose or use it more frequently than once a day (for on-demand tablets) [4]. If you are prescribed the daily low-dose form, take it at the same time each day. Tadalafil can be taken with or without food, though a very large or high-fat meal may delay its effect slightly.

Be aware of how you feel when you first start tadalafil. Both flecainide and tadalafil can cause dizziness, so take care when standing up quickly, especially in the first few days. Avoid drinking large amounts of alcohol, as this can increase the risk of dizziness and low blood pressure, and can also make erectile dysfunction worse [1]. Do not drink grapefruit juice regularly, as it can raise tadalafil levels in your blood. If you experience chest pain, severe dizziness, fainting, palpitations, or any new or worsening symptoms, stop taking tadalafil and seek medical advice immediately.

When to seek urgent help and ongoing monitoring

Seek emergency medical help (call 999 or go to A&E) if you experience chest pain during or after sexual activity, a sudden loss of vision or hearing, or an erection that lasts longer than four hours (priapism) [1][4]. If you have a very fast, slow, or irregular heartbeat, severe dizziness, fainting, or breathlessness, seek urgent medical attention, as these could be signs of a heart rhythm problem or other serious condition.

Keep all your follow-up appointments with your cardiologist or GP to monitor your heart rhythm and overall heart health. If your flecainide dose changes, or if you are started on any new medicine, inform your prescriber before your next tadalafil order. Do not stop taking flecainide or any other prescribed medicine without medical advice. If you have any concerns about taking tadalafil and flecainide together, or if you experience side effects, contact your GP, pharmacist, or the Cured Pharmacy clinical team for advice. All ED treatments at Cured Pharmacy are supplied only after a consultation reviewed by a UK-registered prescriber, ensuring your safety and suitability for treatment.

Other ED treatment options

If tadalafil is not suitable for you, or if you would prefer a different option, other PDE5 inhibitors are available, including sildenafil (Viagra), vardenafil (Levitra), and avanafil (Spedra) [3][5][6]. Each has a slightly different duration of action and onset time, and your prescriber will discuss which may be most appropriate for your circumstances. Non-tablet treatments, such as alprostadil (Vitaros cream or Caverject injection) or the Eroxon gel, may also be considered if oral medicines are not suitable [7]. Always consult a healthcare professional to find the safest and most effective treatment for you.

In summary

• Tadalafil and flecainide have no major direct interaction and can often be taken together safely
• Your prescriber will check your heart health and arrhythmia stability before approving tadalafil
• Never take tadalafil with nitrates, nicorandil, riociguat, or poppers—this is dangerous
• Report dizziness, chest pain, palpitations, or fainting to a doctor immediately
• Declare all medicines during your consultation for a safe, personalised assessment

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