Sildenafil and Candesartan: Can They Be Taken Together?

Takes less than 2 minutes to complete 100% online

What is Candesartan and Why is it Prescribed?

Candesartan is a medicine used to treat high blood pressure (hypertension) and heart failure. It belongs to a group of medicines called angiotensin-II receptor blockers, or ARBs for short. These medicines work by blocking the action of a hormone called angiotensin-II, which normally causes blood vessels to narrow. By blocking this hormone, candesartan allows your blood vessels to relax and widen, which lowers your blood pressure and reduces the strain on your heart.

High blood pressure is very common in the UK and often has no symptoms, but over time it can increase your risk of serious problems such as heart attacks, strokes, and kidney disease. Candesartan helps to protect against these complications by keeping blood pressure at a healthier level. It is usually taken once a day, and many people take it for the long term to manage their blood pressure effectively.

What is Sildenafil and How Does it Work?

Sildenafil is a medicine used to treat erectile dysfunction (ED), the difficulty in getting or keeping an erection firm enough for sex. It is the active ingredient in Viagra and is also available as a lower-cost generic medicine. Sildenafil belongs to a group of medicines called PDE5 inhibitors, which work by increasing blood flow to the penis when you are sexually aroused [3].

When you are sexually stimulated, your body releases a chemical called nitric oxide in the penis, which triggers a chain reaction that relaxes the blood vessels and allows more blood to flow in. An enzyme called PDE5 normally breaks down the chemicals involved in this process. Sildenafil blocks PDE5, which means the blood vessels stay relaxed for longer and blood flow is improved, making it easier to get and maintain an erection. It is important to understand that sildenafil only works when you are sexually aroused; it does not cause an automatic erection and it does not increase sexual desire [1].

Sildenafil is typically taken about one hour before sexual activity, and its effects can last for around four to five hours. The usual starting dose is 50 mg, but your prescriber may adjust this to 25 mg or 100 mg depending on how well it works for you and whether you experience any side effects [3].

Licensed Doses and Timing

In the UK, sildenafil is available in 25 mg, 50 mg, and 100 mg tablets. The recommended starting dose for most men is 50 mg, taken approximately one hour before sexual activity, and no more than once in a 24-hour period. Your prescriber may lower the dose to 25 mg if you experience side effects, or increase it to 100 mg if the 50 mg dose is not effective enough. Sildenafil needs sexual stimulation to work, so simply taking the tablet will not cause an erection on its own [3].

When to get urgent help

• Chest pain during or after sex – call 999 immediately
• An erection lasting more than 4 hours (priapism) – go to A&E
• Sudden loss of vision or hearing – seek urgent medical help
• Severe dizziness, fainting, or very low blood pressure – contact your GP or call 111
• Allergic reaction (swelling of face, lips, tongue, difficulty breathing) – call 999

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

How Do Sildenafil and Candesartan Interact?

Sildenafil and candesartan can both lower blood pressure, so when taken together there is a potential for an additive effect, meaning your blood pressure might drop more than it would with either medicine alone. This is not the same as the dangerous interaction that occurs with nitrate medicines (such as GTN spray), where the combination is absolutely contraindicated. With candesartan, the interaction is generally manageable, but it does require careful assessment by your prescriber.

Candesartan lowers blood pressure by relaxing and widening your blood vessels throughout the body. Sildenafil also has a mild blood-pressure-lowering effect because it relaxes blood vessels, although its main action is focused on the blood vessels in the penis. When you take both medicines together, the combined effect on your blood pressure can sometimes cause symptoms such as dizziness, light-headedness, or feeling faint, especially when you stand up quickly [3].

For most men whose blood pressure is well controlled on candesartan, taking sildenafil is safe and effective. However, your prescriber will check your current blood pressure readings, review your full medication list, and assess your overall cardiovascular health before approving sildenafil. If your blood pressure is very low or poorly controlled, or if you have other heart conditions, sildenafil may not be suitable, or your prescriber may recommend starting with a lower dose and monitoring you closely.

The Mechanism in Plain English

Think of your blood vessels as a network of flexible tubes. Candesartan keeps these tubes relaxed and open by blocking a hormone that would normally make them tighten. Sildenafil also relaxes blood vessels, particularly in the penis, by blocking an enzyme called PDE5. When both medicines are working at the same time, the relaxation effect can add up, which means your blood pressure may drop a bit more than usual. For most people this is not a problem, but it is why your prescriber needs to check that your blood pressure is stable and not already too low before prescribing sildenafil.

What Your Prescriber Checks Before Approving Sildenafil and Candesartan Together

When you request sildenafil through an online consultation at Cured Pharmacy, a UK-registered prescriber will review your medical history and current medications to ensure the treatment is safe for you. If you are taking candesartan, the prescriber will pay particular attention to several key factors.

First, they will check your current blood pressure readings. If your blood pressure is well controlled and not too low, sildenafil is usually safe to use. However, if your blood pressure is very low (for example, systolic below 90 mmHg), sildenafil may not be suitable because it could lower it further and cause symptoms such as dizziness or fainting. Second, the prescriber will review your full list of medicines to check for any other interactions. For example, if you are also taking an alpha-blocker such as doxazosin or tamsulosin (often used for prostate symptoms), this adds another layer of blood-pressure-lowering effect, and the prescriber will need to ensure you are stable on the alpha-blocker and may start you on a lower dose of sildenafil.

Third, the prescriber will assess your cardiovascular health more broadly. Erectile dysfunction can be an early warning sign of heart disease or diabetes, so if you have not seen your GP recently, the prescriber may recommend a check-up [1]. They will also ask about any history of heart attack, stroke, angina, or heart failure, because sexual activity itself places demands on your heart, and sildenafil is not suitable if sexual activity is inadvisable for you. Finally, the prescriber will check that you are not taking any medicines that are absolutely contraindicated with sildenafil, such as nitrates (GTN spray, isosorbide mononitrate), nicorandil, or riociguat [3].

At a glance

Practical Advice for Taking Sildenafil and Candesartan Safely

If your prescriber approves sildenafil while you are taking candesartan, there are some practical steps you can take to minimise the risk of side effects and get the best results from your treatment. First, take both medicines exactly as prescribed. Do not increase the dose of sildenafil without consulting your prescriber, and do not skip doses of candesartan or adjust the timing without medical advice.

Be aware of the symptoms of low blood pressure, which can include dizziness, light-headedness, feeling faint, or blurred vision. These symptoms are more likely to occur when you stand up quickly, so take your time when getting up from sitting or lying down, especially in the first few hours after taking sildenafil. If you do feel dizzy, sit or lie down until the feeling passes. Avoid drinking large amounts of alcohol when taking sildenafil, as alcohol can lower your blood pressure further and also make it harder to get an erection [3].

It is also a good idea to monitor your blood pressure at home if you have a monitor, especially when you first start taking sildenafil. Keep a record of your readings and share them with your GP or prescriber if you have any concerns. If you experience persistent dizziness, fainting, chest pain during sex, or an erection lasting more than four hours, seek medical help immediately. Finally, remember that sildenafil is most effective when you are relaxed and sexually aroused, so try to reduce stress and create a comfortable environment for intimacy.

When to Seek Medical Advice

You should contact your GP or prescriber if you experience persistent dizziness, fainting, or very low blood pressure readings while taking sildenafil and candesartan together. Seek urgent medical help (call 999 or go to A&E) if you develop chest pain during sex, an erection lasting more than four hours (priapism), or sudden loss of vision or hearing. These are rare but serious side effects that require immediate attention [3]. If you have any concerns about how the medicines are working together, or if you want to adjust your dose, always speak to a healthcare professional rather than making changes on your own.

Other Blood Pressure Medicines and Sildenafil: What You Need to Know

Candesartan is just one of many medicines used to treat high blood pressure, and it is helpful to understand how sildenafil interacts with other common blood pressure treatments. Most blood pressure medicines, including ACE inhibitors (such as ramipril or lisinopril), calcium channel blockers (such as amlodipine), and diuretics (such as bendroflumethiazide), can be taken safely with sildenafil, but the same principle applies: both types of medicine can lower blood pressure, so your prescriber will check that the combination is safe for you.

Alpha-blockers, such as doxazosin, tamsulosin, alfuzosin, and terazosin, require special caution. These medicines are often used to treat symptoms of an enlarged prostate, but they also lower blood pressure. When combined with sildenafil, there is a higher risk of dizziness and fainting, so your prescriber will ensure you are stable on the alpha-blocker before starting sildenafil, and will usually recommend the lowest effective dose of sildenafil [3].

Beta-blockers, such as bisoprolol or atenolol, are another common type of blood pressure medicine. They can be taken with sildenafil, but beta-blockers themselves can sometimes contribute to erectile dysfunction, so if you have developed ED since starting a beta-blocker, it is worth discussing this with your GP, as there may be alternative treatments available. Whatever blood pressure medicine you are taking, always declare it during your online consultation, as the prescriber needs a complete picture of your medications to assess safety [2].

Medicines That Must Not Be Taken with Sildenafil

There are some medicines that you must never take with sildenafil because the combination can cause a dangerous drop in blood pressure. These include nitrate medicines such as glyceryl trinitrate (GTN) spray, isosorbide mononitrate, and isosorbide dinitrate, which are used to treat angina. You must also not take sildenafil with nicorandil (another angina medicine) or riociguat (used for pulmonary hypertension). Recreational drugs known as 'poppers' (amyl nitrite or alkyl nitrites) are also absolutely contraindicated with sildenafil. Never take more than one PDE5 inhibitor at the same time (for example, do not combine sildenafil with tadalafil or vardenafil) [3].

In summary

• Sildenafil and candesartan can usually be taken together if your blood pressure is well controlled.
• Both medicines can lower blood pressure, so your prescriber will check your readings and heart health.
• Symptoms of low blood pressure include dizziness and light-headedness; sit down if you feel faint.
• Never take sildenafil with nitrates, nicorandil, or riociguat – this combination is dangerous.
• Declare all your medicines during the online consultation so the prescriber can assess safety.

Faq