Tadalafil and Mysimba: Can You Take Them Together?

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At a glance

What is tadalafil and how does it work?

Tadalafil (also known by the brand name Cialis) 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 the blood vessels in the penis, allowing more blood to flow in when you are sexually aroused [1]. Unlike some other ED treatments, tadalafil can remain effective in your body for up to 36 hours, which is why it is sometimes called the 'weekend pill' [4].

Tadalafil is available in two forms: on-demand tablets (usually 10 mg or 20 mg taken at least 30 minutes before sexual activity) and daily low-dose tablets (2.5 mg or 5 mg taken once a day) [4]. Both options require sexual stimulation to work—tadalafil will not cause an erection on its own. It is broken down in the liver by an enzyme called CYP3A4, which means other medicines that affect this enzyme can change how tadalafil works in your body [4].

Common side effects of tadalafil include headache, indigestion, back pain, muscle aches, flushing, and a blocked or runny nose [4]. Most side effects are mild and short-lived. Tadalafil is not suitable for everyone, particularly men taking nitrates for angina, those with severe heart or liver problems, or anyone who has had a recent stroke or heart attack [4]. Your prescriber will review your full medical history before prescribing tadalafil.

What is Mysimba and why is it prescribed?

Mysimba is a prescription medicine used for weight management in adults who are obese (BMI 30 or above) or overweight (BMI 27 or above) with weight-related health problems such as type 2 diabetes or high blood pressure [12]. It contains two active ingredients: naltrexone (an opioid receptor antagonist) and bupropion (an antidepressant and smoking-cessation aid). Together, these work on areas of the brain that control appetite and food cravings, helping you eat less and lose weight when combined with a reduced-calorie diet and increased physical activity [12].

Bupropion is the component most relevant when considering interactions with other medicines. It affects several brain chemicals, including dopamine and noradrenaline, and is broken down in the liver by enzymes including CYP2B6 [12]. Bupropion can also affect other liver enzymes, which means it may change the levels of some medicines in your body. Common side effects of Mysimba include nausea, constipation, headache, vomiting, dizziness, insomnia, dry mouth, and diarrhoea [12].

Mysimba is not suitable for everyone. It must not be used if you have uncontrolled high blood pressure, a history of seizures, an eating disorder, or if you are taking certain other medicines including monoamine oxidase inhibitors (MAOIs) [12]. Your prescriber will check your blood pressure regularly while you are taking Mysimba, as it can cause increases in blood pressure and heart rate in some people.

Why men taking Mysimba may also need ED treatment

Obesity and being overweight are known risk factors for erectile dysfunction [10]. Excess weight can damage blood vessels, reduce testosterone levels, and contribute to conditions such as type 2 diabetes and high blood pressure—all of which can affect erections [1]. Many men who are prescribed Mysimba for weight loss may also experience ED and seek treatment with medicines like tadalafil. Losing weight can improve erectile function over time, but ED treatment may still be needed in the short or medium term [2].

Is there an interaction between tadalafil and Mysimba?

No major direct pharmacological interaction between tadalafil and Mysimba (naltrexone/bupropion) is commonly reported in clinical practice or standard drug-interaction databases [2][4]. This means the two medicines do not directly interfere with each other's breakdown or action in the body in a way that would make the combination unsafe for most people. However, 'no major interaction' does not mean the combination is automatically suitable for everyone—it simply means your prescriber can consider both medicines together after a thorough review of your individual circumstances.

Both tadalafil and Mysimba can affect your cardiovascular system. Tadalafil lowers blood pressure slightly (because it relaxes blood vessels), while Mysimba can raise blood pressure and heart rate in some people [4][12]. If you have high blood pressure or heart disease, your prescriber will need to check that your blood pressure is well controlled before prescribing tadalafil, and will monitor it regularly if you are also taking Mysimba. The combination is not automatically ruled out, but it does require careful assessment.

Bupropion (one of the ingredients in Mysimba) is broken down by different liver enzymes to tadalafil, so it does not significantly change tadalafil levels in your blood [4][12]. Similarly, tadalafil does not affect how Mysimba is processed. This is reassuring from a drug-metabolism perspective. However, every person's medical history is unique, so your prescriber or pharmacist will review all your current medicines, health conditions, and any symptoms during your consultation before confirming that tadalafil is safe for you.

What you need to know

• No major direct interaction is reported between tadalafil and Mysimba in most people.
• Your prescriber will check your blood pressure and heart health before approving the combination.
• Always declare every medicine you take in your online consultation.
• Monitor for dizziness, chest pain, or severe headache and seek help if these occur.
• Losing weight on Mysimba may improve ED over time, but treatment may still be needed.

What will your prescriber check before approving tadalafil and Mysimba together?

When you request tadalafil through Cured Pharmacy's online consultation, a UK-registered prescriber will review your answers carefully, especially if you are taking Mysimba or any other medicine [2]. They will check your current blood pressure, because Mysimba can increase it and tadalafil can lower it—your blood pressure must be stable and within a safe range for sexual activity [4][12]. If your blood pressure is uncontrolled or very high, tadalafil may not be suitable until it is better managed.

Your prescriber will also ask about your heart health. Sexual activity itself places demands on your heart, and both ED and obesity are linked to cardiovascular disease [1][10]. If you have a history of heart attack, stroke, unstable angina, severe heart failure, or certain heart rhythm problems, tadalafil may not be safe regardless of whether you take Mysimba [4]. Your prescriber may ask you to see your GP for a cardiovascular check-up before starting ED treatment, particularly if you have not had one recently.

Finally, your prescriber will review all your other medicines to check for any that must not be taken with tadalafil. These include nitrates (such as GTN spray or isosorbide mononitrate), nicorandil, riociguat, and recreational drugs called 'poppers' (alkyl nitrites)—do not take tadalafil if you use any of these, as the combination can cause a dangerous drop in blood pressure [3][4]. Alpha-blockers (such as tamsulosin or doxazosin, often used for prostate symptoms) also require caution and a lower starting dose of tadalafil [4]. Always list every medicine, supplement, and recreational substance you use in your consultation.

The role of the online consultation

At Cured Pharmacy, every prescription medicine is supplied only after an online consultation reviewed by a UK-registered prescriber. You will be asked about your medical history, current medicines (including Mysimba), blood pressure, heart health, and any symptoms you have noticed. This is not a tick-box exercise—it is a clinical assessment to make sure tadalafil is safe and appropriate for you. If the prescriber has any concerns, they may ask for more information, suggest seeing your GP first, or recommend a different treatment.

Practical advice for taking tadalafil and Mysimba safely

If your prescriber approves tadalafil while you are taking Mysimba, follow the dosing instructions for both medicines carefully. Take tadalafil as directed—either on-demand (at least 30 minutes before sexual activity, no more than once a day) or as a daily low dose at the same time each day [4]. Do not take more than the prescribed dose, and do not combine tadalafil with another PDE5 inhibitor such as sildenafil or vardenafil. Take Mysimba exactly as your doctor has prescribed, usually building up gradually to two tablets twice a day [12].

Monitor your blood pressure if you have access to a home monitor, or arrange regular checks with your GP or pharmacist. If you notice symptoms such as severe headache, chest pain, shortness of breath, dizziness, or fainting, stop taking both medicines and seek medical advice immediately. These could be signs that your blood pressure is too high or too low, or that your heart is under strain. Remember that heavy alcohol can worsen erectile dysfunction, increase the risk of side effects from both medicines, and add to blood-pressure changes—limit your alcohol intake [1][4].

Be aware of the warning signs that require urgent help. If you develop an erection lasting more than four hours (priapism), sudden loss of vision or hearing, or chest pain during sexual activity, call 999 or go to A&E straight away [4]. These are rare but serious side effects of tadalafil. If you experience severe nausea, vomiting, seizures, or signs of an allergic reaction (such as swelling of the face or throat, difficulty breathing, or severe rash) while taking Mysimba, seek emergency medical help [12]. Never stop a prescribed medicine suddenly without advice—speak to your prescriber or GP if you have concerns.

When to get urgent help

• Erection lasting more than 4 hours (priapism) — call 999 or go to A&E immediately
• Sudden loss of vision or hearing — stop tadalafil and seek emergency medical help
• Chest pain during or after sexual activity — call 999; do not take more tadalafil
• Severe dizziness, fainting, or signs of very low blood pressure — seek urgent medical advice
• Seizure, severe allergic reaction (swelling, difficulty breathing), or signs of serotonin syndrome while on Mysimba — call 999

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

Other medicines and lifestyle factors to consider with tadalafil and Mysimba

In addition to the medicines already mentioned, some other drugs can interact with tadalafil or Mysimba. Potent CYP3A4 inhibitors—such as ritonavir, cobicistat (found in some HIV medicines), ketoconazole, itraconazole, and clarithromycin—can increase tadalafil levels in your blood, requiring a lower dose [4]. CYP3A4 inducers like rifampicin, carbamazepine, phenytoin, and St John's wort can reduce tadalafil's effectiveness [4]. Mysimba must not be taken with MAOIs (a type of antidepressant) or within 14 days of stopping one, and caution is needed with other medicines that affect serotonin or lower the seizure threshold [12].

Grapefruit juice can raise tadalafil levels and should be avoided or limited [4]. If you take other blood-pressure medicines (such as ACE inhibitors, calcium-channel blockers, or diuretics), the blood-pressure-lowering effect of tadalafil may be more noticeable—this is usually manageable but must be declared in your consultation [4]. Mysimba can interact with medicines broken down by the liver enzyme CYP2D6, including some antidepressants, antipsychotics, and beta-blockers; your prescriber will check these [12].

Lifestyle changes can support both weight loss and erectile function. A healthy diet, regular physical activity, stopping smoking, reducing alcohol, and managing stress all improve cardiovascular health and can enhance the effectiveness of both Mysimba and tadalafil [1][2]. Losing weight through Mysimba may improve your ED over time, but do not stop tadalafil without discussing it with your prescriber. If your ED is new or worsening, see your GP—it can be an early warning sign of heart disease or diabetes [1][2].

When to speak to your GP

If you have not seen your GP about your erectile dysfunction, make an appointment. ED can be an early sign of cardiovascular disease, diabetes, or hormonal problems, and your GP can arrange tests and address underlying causes [1][2]. If you are taking Mysimba and notice new or worsening ED, mention this to your doctor—it may be related to your weight, blood pressure, or another health issue that needs attention. Your GP can also review all your medicines and refer you to a specialist if needed.