Sildenafil and Dapagliflozin: Can You Take Them Together?

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Key takeaways

• No major direct interaction is reported between sildenafil and dapagliflozin in clinical practice.
• Both medicines can lower blood pressure slightly, so your prescriber checks your overall health carefully.
• Never take sildenafil with nitrates, nicorandil, riociguat, poppers, or another PDE5 inhibitor.
• Stay hydrated, avoid heavy alcohol, and report dizziness or chest pain to your doctor.
• All prescription ED treatments at Cured Pharmacy require a consultation with a UK prescriber.

What is sildenafil and dapagliflozin?

Sildenafil is a medicine used to treat erectile dysfunction (ED), the difficulty in getting or keeping an erection firm enough for sex [1]. It belongs to a group of medicines called PDE5 inhibitors, which work by relaxing blood vessels in the penis, allowing more blood to flow in when you are sexually aroused [3]. Sildenafil is the active ingredient in Viagra and is available in doses of 25mg, 50mg, and 100mg. You take it about one hour before sexual activity, and it works only when you are sexually stimulated.

Dapagliflozin is a type 2 diabetes medicine from a class called SGLT2 inhibitors. It works by helping your kidneys remove excess sugar from your blood through your urine. Dapagliflozin is also used to treat heart failure and chronic kidney disease because it has protective effects on the heart and kidneys. Common brand names include Forxiga and Edistride. It is usually taken once a day, with or without food.

Both medicines are prescription-only in the UK. If you are taking dapagliflozin for diabetes or heart conditions and are considering treatment for ED, your prescriber will review your full medical history and all your current medicines to ensure sildenafil is safe and appropriate for you.

Do sildenafil and dapagliflozin interact with each other?

No major direct interaction between sildenafil and dapagliflozin is commonly reported in clinical practice. These medicines work through different mechanisms in the body: sildenafil affects blood flow to the penis by inhibiting an enzyme called PDE5, while dapagliflozin works on the kidneys to remove sugar from the blood [3]. They do not interfere with each other's metabolism or effectiveness in a clinically significant way.

However, both medicines can have an effect on blood pressure. Sildenafil can cause a small drop in blood pressure, which is usually mild and temporary [3]. Dapagliflozin can also lower blood pressure slightly, particularly when you first start taking it or if you are dehydrated. When taken together, these effects could add up, potentially causing dizziness or light-headedness, especially when you stand up quickly.

This does not mean the combination is unsafe, but it does mean your prescriber needs to check your blood pressure, your overall cardiovascular health, and any other medicines you are taking. If you are already stable on dapagliflozin and your blood pressure is well controlled, adding sildenafil is usually manageable. Your prescriber may start you on a lower dose of sildenafil to minimise any risk.

How the combination affects blood pressure

The main consideration when taking sildenafil and dapagliflozin together is the potential for additive blood pressure lowering. Sildenafil relaxes blood vessels, which can reduce blood pressure temporarily, particularly in the first few hours after taking it [3]. Dapagliflozin can also lower blood pressure because it reduces fluid volume in the body by increasing urination. If you are taking other blood pressure medicines, such as ACE inhibitors, ARBs, or diuretics, the effect may be more noticeable. Your prescriber will review all your medicines and may adjust doses or advise you to monitor for symptoms such as dizziness, fainting, or feeling light-headed. Staying well hydrated and avoiding heavy alcohol can help reduce these risks.

At a glance

What does your prescriber check before prescribing sildenafil and dapagliflozin?

Before prescribing sildenafil to someone already taking dapagliflozin, your prescriber will carry out a thorough assessment. They will ask about your medical history, including any heart or blood vessel problems, recent heart attack or stroke, blood pressure, kidney or liver function, and any history of eye or blood disorders [2]. They will also check all the medicines you are currently taking, including over-the-counter medicines, herbal supplements, and recreational drugs.

Your prescriber will specifically check whether you are taking any medicines that must not be combined with sildenafil. These include nitrates (such as GTN spray, isosorbide mononitrate, or isosorbide dinitrate), nicorandil, riociguat, or amyl/alkyl nitrites (poppers). Combining sildenafil with any of these can cause a dangerous drop in blood pressure [3]. You must never take sildenafil with another PDE5 inhibitor, such as tadalafil, vardenafil, or avanafil.

If you are taking alpha-blockers (such as doxazosin or tamsulosin) for prostate problems, your prescriber will ensure you are stable on that medicine and will start you on the lowest dose of sildenafil [3]. They will also check for medicines that can raise sildenafil levels in the blood, such as ritonavir, cobicistat, ketoconazole, itraconazole, or clarithromycin, and adjust the dose accordingly. Your prescriber will also ask about your blood pressure control, any symptoms of dehydration, and whether you have had any episodes of low blood pressure or dizziness.

Practical advice for taking sildenafil with dapagliflozin

If your prescriber approves the combination of sildenafil and dapagliflozin, there are some practical steps you can take to use both medicines safely. Take sildenafil about one hour before you plan to have sex, on an empty stomach or after a light meal, as a heavy or high-fat meal can delay how quickly it works [3]. Continue taking your dapagliflozin exactly as prescribed, usually once a day at the same time each day.

Stay well hydrated, especially if you are taking dapagliflozin, as it increases urination and can lead to dehydration. Dehydration can make low blood pressure worse. Avoid drinking large amounts of alcohol, as this can worsen erectile dysfunction, increase the risk of dizziness, and add to the blood pressure-lowering effects of both medicines [1]. Grapefruit juice can raise sildenafil levels in the blood, so it is best to avoid it.

If you feel dizzy or light-headed, especially when standing up, sit or lie down until the feeling passes. If you experience chest pain during sex, stop immediately and seek urgent medical help. Do not take a nitrate medicine (such as GTN spray) if you have taken sildenafil within the last 24 hours, as this combination can be dangerous [3]. Always tell any healthcare professional treating you that you are taking both sildenafil and dapagliflozin.

Monitoring and follow-up

Your GP or diabetes specialist will usually monitor your blood pressure and kidney function regularly while you are on dapagliflozin. If you start taking sildenafil, it is a good idea to mention this at your next review so your healthcare team can check that your blood pressure remains stable. If you notice any new symptoms, such as persistent dizziness, fainting, swelling of the ankles, or changes in urination, contact your GP. If sildenafil does not work well for you, or if you experience side effects, your prescriber can consider alternative ED treatments, such as tadalafil, vardenafil, or avanafil, or adjust the dose.

Warning signs and when to seek help with sildenafil and dapagliflozin

Most men can take sildenafil and dapagliflozin together without problems, but it is important to know the warning signs that need urgent attention. If you have an erection that lasts longer than four hours (priapism), go to A&E immediately, as this can cause permanent damage if not treated quickly [3]. Sudden loss of vision in one or both eyes, or sudden decrease or loss of hearing, are rare but serious side effects of sildenafil and require urgent medical help [3].

If you experience chest pain, severe dizziness, or fainting during or after sex, stop what you are doing and call 999. Do not take a nitrate medicine if you have used sildenafil in the last 24 hours [3]. If you develop symptoms of diabetic ketoacidosis while taking dapagliflozin—such as feeling very thirsty, passing urine more often, feeling sick, being sick, stomach pain, fast or deep breathing, confusion, or unusual tiredness—seek urgent medical advice, even if your blood sugar is not very high.

If you notice signs of a genital infection (such as itching, redness, swelling, or unusual discharge), contact your GP, as SGLT2 inhibitors like dapagliflozin can increase the risk of these infections. If you have any concerns about side effects or how the medicines are working, speak to your GP or pharmacist. Never stop taking dapagliflozin suddenly without medical advice, as it is an important medicine for managing your diabetes or heart condition.

Other erectile dysfunction treatments and dapagliflozin

If sildenafil is not suitable for you, or if you would prefer a different option, there are other licensed ED treatments available in the UK. Tadalafil (Cialis) is another PDE5 inhibitor that can be taken on-demand or as a lower daily dose; its effects can last up to 36 hours, which some men find more convenient [4]. Vardenafil (Levitra) and avanafil (Spedra) are also PDE5 inhibitors with slightly different onset times and durations [5][6]. The same considerations about blood pressure and drug interactions apply to all PDE5 inhibitors when taken with dapagliflozin.

All PDE5 inhibitors must not be taken with nitrates, nicorandil, riociguat, poppers, or another PDE5 inhibitor [3][4][5][6]. Your prescriber will check your full medication list and medical history before recommending any ED treatment. If oral medicines are not suitable or effective, other options include Vitaros (alprostadil cream applied to the tip of the penis) or Caverject (alprostadil injection), both of which are prescription-only [7].

Eroxon is a topical gel medical device that can be bought without a prescription and works by creating a cooling then warming sensation to increase blood flow. Viagra Connect (sildenafil 50mg) and Cialis Together (tadalafil 10mg) are available from pharmacies after a consultation with a pharmacist, but you should still tell the pharmacist about your dapagliflozin and any other medicines you take. At Cured Pharmacy, all prescription ED treatments are supplied only after an online consultation reviewed by a UK-registered prescriber, ensuring your safety and suitability.

Why erectile dysfunction matters in diabetes

Erectile dysfunction is more common in men with diabetes, affecting around half of men with the condition [1]. High blood sugar over time can damage blood vessels and nerves, including those needed for erections. ED can also be an early warning sign of heart disease, so it is important to see your GP if you are experiencing new or worsening erection problems [2]. Managing your diabetes well—through medication like dapagliflozin, healthy eating, regular physical activity, and not smoking—can help improve ED and reduce your risk of complications. Treating ED can improve quality of life and confidence, and modern treatments like sildenafil are effective and well-tolerated in most men with diabetes [9].

When to get urgent help

• Erection lasting more than 4 hours (priapism) — go to A&E immediately
• Sudden loss of vision or hearing — seek urgent medical help
• Chest pain during or after sex — call 999; do not take nitrates if you have used sildenafil in the last 24 hours
• Severe dizziness, fainting, or feeling very unwell — call 999 or go to A&E
• Symptoms of diabetic ketoacidosis (very thirsty, frequent urination, nausea, stomach pain, confusion) — seek urgent medical advice

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