Tadalafil and Chloroquine: Can They Be Taken Together?

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Key takeaways

• No major direct interaction is commonly reported between tadalafil and chloroquine, but both can affect the heart.
• Your prescriber will review your full medical history and current medicines during your consultation.
• Never take tadalafil with nitrates, nicorandil, riociguat, or another PDE5 inhibitor.
• Declare all medicines, including chloroquine, during your online consultation for safe prescribing.
• Seek urgent help if you experience chest pain, an erection lasting over four hours, or sudden vision loss.

What is tadalafil and how does it work?

Tadalafil is the generic name for Cialis, a prescription medicine licensed in the UK to treat erectile dysfunction (ED) [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. Tadalafil does not cause an erection by itself—sexual stimulation is still needed.

Tadalafil is available in two forms: on-demand tablets (10 mg or 20 mg) taken at least 30 minutes before sexual activity, with effects lasting up to 36 hours, and daily tablets (2.5 mg or 5 mg) taken once a day to allow more spontaneity [4]. The long duration of action is why tadalafil is sometimes called the 'weekend pill'. At Cured Pharmacy, tadalafil is available from £7.95 after an online consultation with a UK prescriber.

Like all medicines, tadalafil can interact with other drugs, particularly those that affect blood pressure or are metabolised by the same liver enzymes. Your prescriber will review all your current medicines, including over-the-counter treatments and supplements, to ensure tadalafil is safe and suitable for you.

What is chloroquine and what is it used for?

Chloroquine is a prescription medicine primarily used to prevent and treat malaria, a serious infection transmitted by mosquitoes in tropical and subtropical regions. It works by killing the malaria parasites inside red blood cells. Chloroquine is also occasionally prescribed for certain autoimmune conditions such as rheumatoid arthritis and lupus, although hydroxychloroquine is more commonly used for these purposes in the UK.

Chloroquine can affect the heart's electrical activity, particularly the QT interval on an electrocardiogram (ECG). A prolonged QT interval can, in rare cases, lead to a serious irregular heartbeat. This risk is higher in people who already have heart conditions, take other medicines that prolong the QT interval, or have low levels of potassium or magnesium in their blood.

Because chloroquine is used less frequently in the UK today—mainly for travellers to malaria-endemic areas—your GP or travel clinic will assess your individual risk factors before prescribing it. If you are taking chloroquine and are considering treatment for erectile dysfunction, it is essential to declare this during your consultation so your prescriber can review the combination carefully.

At a glance

Do tadalafil and chloroquine interact with each other?

There is no major direct pharmacological interaction commonly reported between tadalafil and chloroquine in standard UK prescribing references [4]. However, both medicines can have effects on the cardiovascular system that require careful consideration. Tadalafil lowers blood pressure slightly, and chloroquine can affect the heart's electrical rhythm, particularly the QT interval.

When two medicines both have potential effects on the heart or blood pressure, prescribers assess the overall risk to the individual patient. This includes checking your medical history, current heart health, other medicines you take, and any conditions that might increase the risk of side effects. For example, if you have a history of heart rhythm problems or take other medicines that prolong the QT interval, your prescriber may need to take extra precautions or consider alternative treatments.

During your online consultation at Cured Pharmacy, you will be asked to list all your current medicines, including chloroquine. A UK-registered prescriber will review your answers to ensure that tadalafil is safe and appropriate for you. If there are any concerns, the prescriber may request further information from your GP or suggest an alternative approach to managing your erectile dysfunction.

What your prescriber will check

Your prescriber will review your full medical history, including any heart conditions, recent heart attacks or strokes, blood pressure levels, and liver or kidney function. They will also check for medicines that are known to interact dangerously with tadalafil, such as nitrates, nicorandil, riociguat, or other PDE5 inhibitors [4]. If you are taking chloroquine, the prescriber will consider why you are taking it, how long you have been on it, and whether you have any risk factors for heart rhythm problems. This thorough review ensures that the combination is as safe as possible for your individual circumstances.

Practical advice for taking tadalafil and chloroquine together

If your prescriber approves tadalafil while you are taking chloroquine, follow the dosing instructions for both medicines carefully. Take tadalafil on-demand tablets at least 30 minutes before sexual activity, or take daily tablets at the same time each day. Do not take more than the prescribed dose, and never take tadalafil more than once in 24 hours [4]. Continue taking chloroquine exactly as your GP or travel clinic has instructed, and do not stop or change the dose without medical advice.

Be aware of how your body responds when you first start tadalafil. Common side effects include headache, indigestion, back pain, muscle aches, flushing, and a blocked or runny nose [4]. These are usually mild and temporary. If you feel dizzy or light-headed, sit or lie down until the feeling passes, and avoid driving or operating machinery. Heavy alcohol can make erectile dysfunction worse and increase the risk of dizziness, so limit your intake.

If you experience any unusual symptoms—such as a fast or irregular heartbeat, chest pain, fainting, or an erection lasting more than four hours—seek medical help immediately. These could be signs of a serious side effect. Always carry a list of your current medicines (including tadalafil and chloroquine) so that any healthcare professional treating you is fully informed.

Other medicines that interact with tadalafil

Tadalafil must never be taken with nitrates (such as GTN spray, isosorbide mononitrate, or isosorbide dinitrate), nicorandil, riociguat, or recreational drugs called 'poppers' (amyl or alkyl nitrites). Combining tadalafil with any of these can cause a dangerous drop in blood pressure [4]. Do not take tadalafil if you are already using another PDE5 inhibitor, such as sildenafil or vardenafil.

Alpha-blockers (for example, doxazosin, tamsulosin, alfuzosin) used to treat high blood pressure or prostate symptoms can also lower blood pressure. If you take an alpha-blocker, you should be stable on that medicine before starting tadalafil, and your prescriber will usually recommend the lowest dose of tadalafil to minimise the risk of dizziness [4].

Potent CYP3A4 inhibitors—medicines such as ritonavir, cobicistat, ketoconazole, itraconazole, and clarithromycin—can increase tadalafil levels in your blood, raising the risk of side effects. Your prescriber will adjust the tadalafil dose if you take any of these [4]. Conversely, CYP3A4 inducers like rifampicin, carbamazepine, phenytoin, and St John's wort can reduce tadalafil's effectiveness. Grapefruit juice may also increase tadalafil levels, so it is best avoided.

Declaring all your medicines

It is essential to list every medicine you take during your consultation, including prescription drugs, over-the-counter treatments, herbal remedies, and supplements. Even medicines you take occasionally—such as antibiotics, antifungals, or pain relief—can interact with tadalafil. Your prescriber relies on accurate information to make safe prescribing decisions, so never leave anything out, even if you think it is unimportant. If you are unsure about a medicine's name, bring the packet or patient information leaflet to your consultation.

When to seek medical advice about tadalafil and chloroquine

If you are already taking chloroquine and are considering treatment for erectile dysfunction, speak to your GP or use an online consultation service like Cured Pharmacy. Do not start tadalafil without a prescriber's approval, as they need to assess your individual risk factors. If you develop new symptoms after starting tadalafil—such as chest pain, palpitations, severe dizziness, or fainting—stop taking the medicine and contact your GP or call NHS 111 for advice.

Erectile dysfunction can be an early warning sign of underlying health conditions, including heart disease, diabetes, or high blood pressure [1]. If you have not already done so, see your GP for a full health check. Treating the underlying cause can sometimes improve ED without the need for medication. Your GP can also review your current medicines to see if any might be contributing to erectile dysfunction.

If you experience an erection lasting more than four hours (priapism), sudden loss of vision in one or both eyes, or sudden hearing loss or ringing in the ears, seek emergency medical help immediately [4]. These are rare but serious side effects that require urgent treatment. Always inform any healthcare professional treating you that you take both tadalafil and chloroquine, so they can provide the safest care.

How Cured Pharmacy can help

Cured Pharmacy is a GPhC-registered online pharmacy (GPhC 9012511) offering discreet, convenient access to erectile dysfunction treatments. After you complete an online consultation, a UK-registered prescriber reviews your answers and medical history to ensure the treatment is safe and suitable for you. If approved, your medicine is dispensed by our pharmacy team and delivered discreetly to your door. You can also message our pharmacists if you have questions about your treatment or any interactions with other medicines you are taking.

When to get urgent help

• An erection lasting more than four hours (priapism)—go to A&E immediately
• Sudden loss of vision in one or both eyes—call 999 or go to A&E
• Chest pain during or after sexual activity—stop and call 999
• Severe dizziness, fainting, or a fast or irregular heartbeat—seek same-day medical advice
• Sudden hearing loss or ringing in the ears—contact your GP urgently or call NHS 111

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

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