Tadalafil and Lamotrigine: Can You Take Them Together?

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At a glance

What is tadalafil and how does it work?

Tadalafil is a prescription medicine used to treat erectile dysfunction (ED) in men. It belongs to a group of medicines called phosphodiesterase type 5 (PDE5) inhibitors [4]. Tadalafil works by relaxing the blood vessels in the penis, which increases blood flow when you are sexually aroused, helping you to get and maintain an erection [1][4].

Tadalafil is available in two forms: on-demand tablets (usually 10 mg or 20 mg) taken at least 30 minutes before sexual activity, with effects lasting up to 36 hours, and daily low-dose tablets (2.5 mg or 5 mg) taken once a day at the same time [4]. Both require sexual stimulation to work. Tadalafil is the generic version of the branded medicine Cialis and is available at Cured Pharmacy following an online consultation with a UK-registered prescriber.

Common side effects include headache, indigestion, back pain, muscle aches, flushing, and nasal congestion [4]. Most side effects are mild and temporary. Tadalafil is not suitable for everyone, particularly men taking nitrates, nicorandil, riociguat, or those for whom sexual activity is inadvisable due to heart conditions [4].

What is lamotrigine and why is it prescribed?

Lamotrigine is an anticonvulsant (anti-epileptic) medicine primarily used to prevent seizures in people with epilepsy. It is also licensed as a mood stabiliser to prevent depressive episodes in adults with bipolar disorder. Lamotrigine works by stabilising electrical activity in the brain, reducing the likelihood of seizures or mood swings.

Lamotrigine is usually started at a low dose and increased gradually over several weeks to reduce the risk of serious skin reactions. It is taken once or twice daily, and the dose varies depending on the condition being treated and whether you are taking other medicines that affect how lamotrigine is broken down in the body.

Common side effects include headache, dizziness, drowsiness, blurred or double vision, nausea, and skin rash. A serious skin rash can occur, particularly in the first eight weeks of treatment, so any new rash should be reported to your doctor immediately. Lamotrigine does not usually cause erectile dysfunction directly, but some men with epilepsy or bipolar disorder may experience ED due to the underlying condition, psychological factors, or other medications they are taking.

Does lamotrigine cause erectile dysfunction?

Lamotrigine itself is not commonly associated with causing erectile dysfunction. However, ED can be more common in men with epilepsy or bipolar disorder for a variety of reasons, including the psychological impact of living with a chronic condition, the effects of other medications, or changes in hormone levels [1][10]. If you have noticed changes in your erections since starting lamotrigine or any other medicine, it is important to discuss this with your GP, as they can help identify the cause and suggest appropriate treatment options.

Is there an interaction between tadalafil and lamotrigine?

No major direct interaction between tadalafil and lamotrigine is commonly reported in clinical practice or listed in the British National Formulary [3][4]. Lamotrigine is not known to significantly affect the way tadalafil is broken down in the body, and tadalafil does not typically alter lamotrigine levels. This means that, for most men, taking tadalafil and lamotrigine together is not expected to cause problems.

However, it is essential to declare all your current medicines—including lamotrigine—during your online consultation. Your prescriber will review your full medication list, medical history, and any other conditions you have to ensure tadalafil is safe and appropriate for you. Some medicines can interact with tadalafil in important ways, so a thorough check is always carried out before treatment is approved.

If you are taking other medicines alongside lamotrigine, such as enzyme-inducing anticonvulsants (for example, carbamazepine or phenytoin), these can reduce the effectiveness of tadalafil by speeding up how quickly it is broken down in the body. Your prescriber will consider all these factors and may adjust your treatment plan accordingly. Never stop or change your prescribed medicine without speaking to your doctor or pharmacist first.

What you need to know

• No major interaction between tadalafil and lamotrigine is commonly reported in clinical practice.
• Always declare lamotrigine and all other medicines during your online consultation.
• Continue taking lamotrigine as prescribed; no dose adjustment is needed when starting tadalafil.
• Enzyme-inducing anticonvulsants like carbamazepine may reduce tadalafil effectiveness.
• See your GP if you experience ED for the first time, as it can signal underlying health conditions.

What does your prescriber check before approving tadalafil and lamotrigine together?

During your online consultation at Cured Pharmacy, you will be asked to list all the medicines you currently take, including lamotrigine, any other prescription medicines, over-the-counter treatments, and herbal supplements. The prescriber will review this information carefully to check for any interactions or contraindications [2][3][4].

The prescriber will also ask about your general health, including your heart and blood pressure, as tadalafil can lower blood pressure slightly and is not suitable for men taking nitrates, nicorandil, riociguat, or those with certain heart conditions [4]. They will check whether you have any history of stroke, heart attack, severe liver or kidney problems, or eye conditions such as non-arteritic anterior ischaemic optic neuropathy (NAION), as these may affect whether tadalafil is safe for you.

If you are taking other anticonvulsants or mood stabilisers alongside lamotrigine, the prescriber will consider whether these medicines might interact with tadalafil. For example, enzyme-inducing anticonvulsants can make tadalafil less effective. The prescriber may recommend starting with a lower dose or choosing a different ED treatment if needed. This thorough review ensures that tadalafil is both safe and likely to be effective for you.

Do you need to adjust your lamotrigine dose?

No, you do not need to adjust your lamotrigine dose when starting tadalafil. Tadalafil does not affect lamotrigine levels in the body, and there is no need to change the dose or timing of your epilepsy or mood stabiliser treatment [3][4]. Continue taking lamotrigine exactly as prescribed by your doctor. If you have any concerns about your lamotrigine treatment or experience any new symptoms, speak to your GP or specialist rather than making changes on your own.

Practical advice for taking tadalafil and lamotrigine safely

If your prescriber approves tadalafil, take it exactly as directed. For on-demand tadalafil (10 mg or 20 mg), take one tablet at least 30 minutes before sexual activity; do not take more than one dose in 24 hours [4]. For daily tadalafil (2.5 mg or 5 mg), take one tablet at the same time each day, whether or not you plan to have sex. Tadalafil can be taken with or without food, although a heavy meal may delay how quickly it works.

Continue taking your lamotrigine at the usual times and doses. There is no need to separate the timing of tadalafil and lamotrigine, as they do not interfere with each other. Avoid drinking large amounts of alcohol when taking tadalafil, as alcohol can make it harder to get an erection and may increase the risk of side effects such as dizziness or low blood pressure [4].

If you experience any side effects from tadalafil—such as headache, indigestion, back pain, or dizziness—these are usually mild and temporary. However, if you develop chest pain during or after sex, an erection lasting more than four hours, or sudden loss of vision or hearing, stop taking tadalafil and seek urgent medical help [4]. Always inform any healthcare professional treating you that you are taking both tadalafil and lamotrigine, especially if you are prescribed new medicines or have surgery.

When to get urgent help

• Erection lasting more than 4 hours (priapism) – go to A&E immediately
• Sudden loss of vision in one or both eyes – stop tadalafil and seek urgent medical help
• Sudden decrease or loss of hearing – stop tadalafil and contact your doctor immediately
• Chest pain during or after sexual activity – stop and call 999; do not take nitrates
• New or worsening skin rash while on lamotrigine – contact your doctor the same day

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

Other medicines and conditions to consider with tadalafil and lamotrigine

While tadalafil and lamotrigine can usually be taken together, it is important to be aware of other medicines that can interact with tadalafil. Never take tadalafil if you are using nitrates (such as GTN spray or isosorbide mononitrate), nicorandil, riociguat, or recreational drugs known as 'poppers' (amyl or alkyl nitrites), as the combination can cause a dangerous drop in blood pressure [3][4].

If you take alpha-blockers for an enlarged prostate or high blood pressure (such as tamsulosin or doxazosin), tell your prescriber, as these can also lower blood pressure when combined with tadalafil. You may need to start on a lower dose of tadalafil and be stable on your alpha-blocker before starting ED treatment [4]. Medicines that strongly inhibit the enzyme CYP3A4—such as ritonavir, cobicistat, ketoconazole, itraconazole, or clarithromycin—can increase tadalafil levels in the body, so your prescriber may reduce the maximum dose [4].

Some anticonvulsants, such as carbamazepine and phenytoin, can reduce the effectiveness of tadalafil by speeding up how quickly it is broken down. If you take these medicines alongside lamotrigine, your prescriber will consider this when recommending treatment. St John's wort, a herbal remedy sometimes used for low mood, can also reduce tadalafil's effectiveness and should be avoided [4]. Always declare every medicine and supplement you take during your consultation, even if you think it is unrelated.

When to see your GP about erectile dysfunction

If you are experiencing erectile dysfunction for the first time, it is important to see your GP for a full assessment [1][2]. ED can be an early warning sign of underlying health conditions such as heart disease, diabetes, or high blood pressure, and treating these conditions can improve your erections and overall health [1][10]. Your GP can also review all your medicines, including lamotrigine, to check whether any of them might be contributing to ED, and discuss treatment options with you. Online consultations at Cured Pharmacy are suitable for men who have already discussed their ED with a healthcare professional and are looking for convenient, discreet access to treatment.

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