Tadalafil and Chlortalidone: 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 phosphodiesterase type 5 (PDE5) inhibitors, which work by relaxing the blood vessels in the penis, allowing increased blood flow when you are sexually aroused [1]. Tadalafil is the generic version of Cialis and is available in two forms: on-demand tablets (10mg or 20mg taken at least 30 minutes before sexual activity) and daily low-dose tablets (2.5mg or 5mg taken once a day) [4].

One of the key advantages of tadalafil is its long duration of action—the effects can last up to 36 hours, which is why it is sometimes called the 'weekend pill' [4]. This does not mean you will have an erection for 36 hours; rather, you may be able to achieve an erection during this window when sexually stimulated. Tadalafil requires sexual arousal to work and will not cause an erection on its own [1]. Like all prescription ED medicines, tadalafil is only supplied after an online consultation reviewed by a UK prescriber, who will check your medical history and current medications.

What Is Chlortalidone and Why Is It Prescribed?

Chlortalidone (sometimes spelled chlorthalidone) is a thiazide-like diuretic—a type of medicine commonly prescribed to treat high blood pressure (hypertension) and fluid retention (oedema). Diuretics are often called 'water tablets' because they help your kidneys remove excess salt and water from your body through urine. By reducing the volume of fluid in your blood vessels, chlortalidone helps to lower blood pressure and reduce the strain on your heart.

High blood pressure is a major risk factor for heart disease, stroke, and kidney problems, so controlling it is essential for long-term health. Chlortalidone is usually taken once a day in the morning, as it can increase urination. It is important to take it exactly as your GP has prescribed and to attend regular blood pressure checks. Some men with high blood pressure also experience erectile dysfunction, which can be related to the underlying cardiovascular condition itself or, occasionally, to the blood-pressure medicine [1]. If you think your blood pressure treatment is affecting your erections, speak to your GP—never stop taking prescribed medication without medical advice.

Can High Blood Pressure Cause Erectile Dysfunction?

Yes, high blood pressure can contribute to erectile dysfunction [1]. Over time, untreated hypertension can damage the lining of blood vessels and reduce blood flow to the penis, making it harder to achieve or maintain an erection [10]. This is one reason why ED can be an early warning sign of cardiovascular disease, and why it is important to see your GP if you develop new erection problems [2]. Treating high blood pressure effectively—with lifestyle changes and medication—can improve overall vascular health and, in some cases, help with erectile function.

When to get urgent help

• An 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; do not take nitrates if you have used tadalafil in the last 48 hours
• Severe dizziness, fainting, or collapse—call 999 or go to A&E
• Allergic reaction (swelling of face, lips, tongue, or difficulty breathing)—call 999

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

How Do Tadalafil and Chlortalidone Interact?

Tadalafil and chlortalidone can usually be taken together, but there is an interaction you and your prescriber need to be aware of. Both medicines can lower blood pressure: tadalafil causes mild vasodilation (widening of blood vessels) as part of its mechanism, and chlortalidone reduces blood pressure by removing excess fluid [3][4]. When taken together, the blood-pressure-lowering effects can add up, which may increase the risk of dizziness, light-headedness, or fainting, especially when you stand up quickly.

This interaction is generally manageable, and many men take a PDE5 inhibitor alongside a diuretic without problems. However, your prescriber will check your current blood pressure control, review all your medications, and may recommend starting tadalafil at a lower dose to minimise the risk of side effects [4]. It is essential to be honest during your consultation about all the medicines you take, including over-the-counter products and supplements, so that the prescriber can make a safe decision tailored to your health.

What Happens in Your Body?

In simple terms, chlortalidone lowers your blood pressure by reducing the amount of fluid in your blood vessels, while tadalafil relaxes and widens blood vessels to improve blood flow to the penis. Both actions can lead to a drop in blood pressure. For most men, this drop is small and well tolerated, but if your blood pressure falls too much, you may feel dizzy or faint. This is why your prescriber will assess your overall cardiovascular health and current blood pressure readings before approving tadalafil.

What Your Prescriber Will Check Before Approving Tadalafil

When you request tadalafil through an online consultation at Cured Pharmacy, a UK-registered prescriber will review your medical history and current medications carefully [2]. They will check whether you are taking chlortalidone or any other blood-pressure medicines, and they will ask about your blood pressure control. If your blood pressure is well controlled and stable on chlortalidone, tadalafil is usually considered safe, but the prescriber may recommend starting with a lower dose (such as 10mg on-demand or 2.5mg daily) to reduce the risk of dizziness [4].

The prescriber will also check for any contraindications—conditions or medicines that make tadalafil unsafe. For example, you must not take tadalafil if you use nitrates (such as GTN spray or isosorbide mononitrate), nicorandil, riociguat, or recreational drugs called 'poppers', because the combination can cause a dangerous drop in blood pressure [3][4]. If you take an alpha-blocker (such as doxazosin or tamsulosin) as well as chlortalidone, the prescriber will be especially cautious, as alpha-blockers also lower blood pressure and interact with PDE5 inhibitors. You should be stable on the alpha-blocker before starting tadalafil, and the lowest dose of the ED medicine will be recommended [4].

At a glance

Practical Advice for Taking Tadalafil and Chlortalidone Together

If your prescriber approves tadalafil while you are taking chlortalidone, there are some practical steps you can take to use both medicines safely. First, take tadalafil exactly as prescribed—do not take more than the recommended dose or take it more often than once a day (for on-demand tablets) [4]. If you are prescribed the daily low-dose version, take it at the same time each day. Continue taking your chlortalidone as your GP has directed; never stop or change your blood pressure medicine without medical advice.

Be aware of the signs of low blood pressure: dizziness, light-headedness, feeling faint, or blurred vision. These are more likely when you first start tadalafil or if you stand up quickly. If you feel dizzy, sit or lie down until it passes, and avoid driving or operating machinery until you know how the medicine affects you [4]. Limit alcohol, as heavy drinking can worsen erectile dysfunction and add to the blood-pressure-lowering effect of both medicines [1]. Stay well hydrated, especially in hot weather or if you are exercising, as chlortalidone increases urination. If you experience persistent dizziness, chest pain during sex, or an erection lasting more than four hours, seek medical help immediately.

When to Contact Your GP or Pharmacist

If you develop new symptoms after starting tadalafil—such as severe dizziness, fainting, swelling of the ankles, or worsening shortness of breath—contact your GP or pharmacist promptly. These could be signs that your blood pressure is too low or that your heart condition needs review. Your GP may want to check your blood pressure and adjust your medications. Remember, erectile dysfunction can be an early sign of heart disease or diabetes, so if you have not already discussed your ED with your GP, it is worth doing so [1][2].

Other Medicines and Lifestyle Factors to Consider

In addition to chlortalidone, you should tell your prescriber about all other medicines you take. If you are on other blood-pressure medicines—such as ACE inhibitors (ramipril, lisinopril), angiotensin receptor blockers (losartan, candesartan), beta-blockers (bisoprolol, atenolol), or calcium-channel blockers (amlodipine, felodipine)—these can also add to the blood-pressure-lowering effect of tadalafil [3][4]. This does not mean you cannot take tadalafil, but your prescriber will assess the overall picture and may start you on a lower dose.

Certain other medicines can affect how tadalafil works. Potent CYP3A4 inhibitors (such as ritonavir, ketoconazole, itraconazole, or clarithromycin) can increase tadalafil levels in your blood, so your prescriber may reduce the maximum dose [4]. CYP3A4 inducers (such as rifampicin, carbamazepine, phenytoin, or St John's wort) can make tadalafil less effective. Grapefruit juice can also raise tadalafil levels, so it is best to avoid it [4]. Lifestyle factors matter too: stopping smoking, losing weight if needed, exercising regularly, and managing stress can all improve erectile function and cardiovascular health [1][2]. If you have diabetes, keeping your blood sugar well controlled is also important for erection quality.

What About Other ED Medicines?

If tadalafil is not suitable for you, there are other PDE5 inhibitors available, such as sildenafil (Viagra), vardenafil (Levitra), and avanafil (Spedra) [3][5][6]. All of these can interact with blood-pressure medicines in a similar way to tadalafil, so the same precautions apply. Your prescriber will help you choose the most appropriate option based on your health, preferences, and how quickly you want the medicine to work. Never take more than one PDE5 inhibitor at the same time, as this can be dangerous [3].

In summary

• Tadalafil and chlortalidone can usually be taken together safely with prescriber approval.
• Both medicines can lower blood pressure; the prescriber may start you on a lower tadalafil dose.
• Watch for dizziness or light-headedness and report any concerns to your GP or pharmacist.
• Never stop chlortalidone without medical advice; your prescriber will check all your medicines.
• Do not take tadalafil with nitrates, nicorandil, riociguat, or poppers—this is dangerous.

Frequently Asked Questions