Tadalafil and Hydralazine: Can They Be Taken Together?
Learn about the interaction, what your prescriber checks, and how to use them safely together.
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Tadalafil and Hydralazine: Understanding the Interaction
Published: 21 October 2026
Many men wonder whether tadalafil and hydralazine can be taken together safely. Tadalafil is a PDE5 inhibitor used to treat erectile dysfunction (ED), while hydralazine is a vasodilator prescribed for high blood pressure and heart failure. Both medicines lower blood pressure, so combining them requires careful assessment by your prescriber to avoid excessive blood pressure drops and dizziness. This page explains how the two medicines interact, what checks your doctor or pharmacist will carry out, and practical steps to use them safely if appropriate for you.
Key takeaways
- Tadalafil and hydralazine both lower blood pressure, so combining them increases the risk of dizziness and fainting.
- The combination is not contraindicated but requires prescriber assessment and often a lower starting dose of tadalafil.
- Stand up slowly, avoid heavy alcohol, and stay hydrated to reduce the risk of low blood pressure symptoms.
- Never take tadalafil with nitrates, nicorandil, riociguat, or poppers—these combinations are dangerous.
- Every tadalafil prescription at Cured Pharmacy follows a UK prescriber consultation to check your medicines and suitability.
What is tadalafil and how does it work?
Tadalafil is a prescription medicine used to treat erectile dysfunction in men. It belongs to a group of medicines called PDE5 inhibitors, which work by relaxing blood vessels in the penis, allowing increased blood flow when you are sexually aroused [3][4]. Tadalafil does not cause an erection on its own—sexual stimulation is still needed.
In the UK, tadalafil is available in two forms: on-demand tablets (10mg or 20mg) taken at least 30 minutes before sexual activity, with effects lasting up to 36 hours, and daily low-dose tablets (2.5mg or 5mg) for men who prefer spontaneity [4]. Tadalafil is the generic name for Cialis. Because it relaxes blood vessels throughout the body, tadalafil can also lower blood pressure slightly, which is why interactions with other blood-pressure medicines matter [4].
What is hydralazine and why is it prescribed?
Hydralazine is a vasodilator medicine used to treat high blood pressure (hypertension) and heart failure. It works by relaxing and widening the blood vessels, which reduces the resistance against which the heart has to pump and lowers blood pressure. Hydralazine is usually prescribed when other blood-pressure medicines have not been effective enough on their own, or as part of combination therapy.
Common brand names in the UK include Apresoline, though many patients receive generic hydralazine. Because hydralazine lowers blood pressure by dilating blood vessels, it can cause side effects such as dizziness, headache, flushing, and a fast heartbeat, especially when standing up quickly. Your doctor will monitor your blood pressure regularly while you are taking hydralazine to ensure it is working safely and effectively.
At a glance
How do tadalafil and hydralazine interact?
Tadalafil and hydralazine both lower blood pressure, so taking them together can add to each other's blood-pressure-lowering effects. This is known as an additive interaction. When two medicines that reduce blood pressure are combined, there is a greater risk of symptoms such as dizziness, light-headedness, fainting, or feeling unsteady—particularly when standing up from sitting or lying down [4].
The interaction is not an absolute contraindication (unlike the dangerous combination of tadalafil with nitrates or nicorandil), but it does require careful assessment and monitoring. Your prescriber will check your current blood pressure, how well controlled it is on hydralazine, and whether you have experienced dizziness or fainting episodes. If your blood pressure is stable and well managed, tadalafil may still be prescribed, often starting at a lower dose to minimise the risk of a sudden drop in blood pressure [4].
Why this interaction matters
A sudden or excessive drop in blood pressure can reduce blood flow to vital organs, including the brain and heart. Symptoms can include dizziness, blurred vision, confusion, fainting, or—in rare cases—chest pain. These effects are more likely if you are dehydrated, have been drinking alcohol, or stand up quickly. While most men tolerate the combination well under medical supervision, it is essential that your prescriber knows about all your blood-pressure medicines before starting tadalafil [4].
What your prescriber will check before combining tadalafil and hydralazine
Before prescribing tadalafil to someone taking hydralazine, your doctor or pharmacist will carry out a thorough assessment. They will ask about your current blood pressure readings, whether you have experienced dizziness or fainting, and how long you have been stable on hydralazine. They will also check for other medicines you are taking that might lower blood pressure further, such as alpha-blockers, other antihypertensives, or nitrates (which are absolutely contraindicated with tadalafil) [2][4].
Your prescriber will review your cardiovascular health, including any history of heart attack, stroke, angina, or heart failure, because sexual activity itself places demands on the heart. If your blood pressure is very low or poorly controlled, tadalafil may not be suitable until your condition is stabilised. In many cases, starting with the lowest effective dose of tadalafil (such as 10mg on-demand or 2.5mg daily) and monitoring your response is the safest approach [4].
At Cured Pharmacy, every prescription for tadalafil follows an online consultation reviewed by a UK-registered prescriber, who will check your full medical history and current medicines to ensure treatment is safe and appropriate for you.
Stand up slowly after taking tadalafil
When you take tadalafil with hydralazine, stand up slowly from sitting or lying down—especially in the first few hours—to give your body time to adjust and reduce the risk of dizziness or fainting.
Practical advice for taking tadalafil with hydralazine
If your prescriber approves the combination of tadalafil and hydralazine, there are several practical steps you can take to reduce the risk of side effects. 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). Avoid heavy alcohol, which can worsen dizziness and make erectile dysfunction worse [4].
Stand up slowly from sitting or lying down, especially in the first few hours after taking tadalafil, to give your body time to adjust to any blood pressure changes. Stay well hydrated, but avoid grapefruit juice, which can raise tadalafil levels in your blood. If you feel dizzy, light-headed, or faint, sit or lie down immediately and contact your doctor if symptoms do not improve quickly [4].
Never stop or change the dose of hydralazine or any other prescribed medicine without speaking to your doctor first. If you experience chest pain during sexual activity, stop immediately, do not take nitrate medicines (such as GTN spray), and seek urgent medical help. Keep all your follow-up appointments so your prescriber can monitor your blood pressure and adjust treatment if needed.
When to seek medical advice
Contact your GP or pharmacist if you develop new or worsening dizziness, fainting episodes, persistent headache, or any other side effects after starting tadalafil. Seek urgent help (call 999 or go to A&E) if you experience chest pain, an erection lasting more than four hours (priapism), sudden loss of vision or hearing, or severe dizziness with confusion or loss of consciousness [1][4].
Other blood-pressure medicines and tadalafil interactions
Hydralazine is just one of many blood-pressure medicines that can interact with tadalafil. Alpha-blockers (such as doxazosin, tamsulosin, alfuzosin) carry a higher risk of low blood pressure and dizziness when combined with PDE5 inhibitors; patients must be stable on the alpha-blocker and start tadalafil at the lowest dose [4]. ACE inhibitors (such as ramipril, lisinopril), angiotensin receptor blockers (such as losartan, candesartan), calcium-channel blockers (such as amlodipine, nifedipine), and diuretics (such as bendroflumethiazide, furosemide) can all add to the blood-pressure-lowering effect of tadalafil, though the interaction is usually manageable with careful monitoring [4].
Nitrates (GTN spray, isosorbide mononitrate or dinitrate), nicorandil, and riociguat are absolutely contraindicated with all PDE5 inhibitors, including tadalafil—do not take these medicines together, as the combination can cause a dangerous, life-threatening drop in blood pressure [3][4]. Amyl or alkyl nitrites (poppers) must also be avoided. Always declare every medicine you are taking, including over-the-counter products and herbal remedies, during your consultation [4].
If you are taking a medicine not listed here, do not assume the combination is safe or unsafe. Your prescriber or pharmacist will check every current medicine during your consultation and advise you accordingly. Never stop or change a prescribed medicine without professional advice.
Tadalafil and hydralazine: the bottom line
Tadalafil and hydralazine can often be taken together under medical supervision, but the combination requires careful assessment because both medicines lower blood pressure. Your prescriber will check your blood pressure control, cardiovascular health, and other medicines before deciding whether tadalafil is suitable for you. If approved, starting at a lower dose and following practical precautions can help you use tadalafil safely and effectively while continuing your hydralazine treatment [4].
When to get urgent help
- Chest pain during or after sexual activity—stop immediately, do not take nitrates, and call 999
- An erection lasting more than 4 hours (priapism)—go to A&E immediately
- Sudden loss of vision or hearing—seek urgent medical help
- Severe dizziness, fainting, or confusion after taking tadalafil—call 999 or go to A&E
- Persistent or worsening symptoms of low blood pressure—contact your GP or call 111 the same day
Call 999 or go to A&E in an emergency, or contact NHS 111 for urgent advice.
Scientific References
- NHS. (n.d.). Erectile dysfunction (impotence). NHS website. https://www.nhs.uk/conditions/erection-problems-erectile-dysfunction/ [accessed 21 October 2026]
- National Institute for Health and Care Excellence. (n.d.). Erectile dysfunction. Clinical Knowledge Summaries. https://cks.nice.org.uk/topics/erectile-dysfunction/ [accessed 21 October 2026]
- Joint Formulary Committee. (n.d.). Sildenafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/sildenafil/ [accessed 21 October 2026]
- Joint Formulary Committee. (n.d.). Tadalafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/tadalafil/ [accessed 21 October 2026]
Information on this page is for educational purposes only and is not medical advice. Prescription treatments require clinical assessment by a UK-registered prescriber. Always consult a qualified healthcare professional before starting or changing any medication.
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Your Questions Answered
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Can I take tadalafil if I am on hydralazine for high blood pressure?
Tadalafil can often be prescribed for men taking hydralazine, but only after a thorough assessment by your prescriber to check your blood pressure is stable and you are not at high risk of dizziness or fainting.
Will tadalafil make my blood pressure drop too low if I take hydralazine?
Both medicines lower blood pressure, so there is a risk of an excessive drop, especially when standing up. Your prescriber will start you on a lower dose and monitor your response to minimise this risk.
What should I do if I feel dizzy after taking tadalafil with hydralazine?
Sit or lie down immediately and avoid standing up quickly. If dizziness persists or you feel faint, contact your GP or pharmacist for advice.
Can I drink alcohol while taking tadalafil and hydralazine together?
Heavy alcohol can worsen dizziness and low blood pressure, and it can also make erectile dysfunction worse. It is best to limit alcohol or avoid it when taking tadalafil.
Are there any blood-pressure medicines I absolutely cannot take with tadalafil?
Yes—do not take tadalafil with nitrates (GTN spray, isosorbide), nicorandil, riociguat, or poppers, as the combination can cause a dangerous drop in blood pressure.
How long after taking tadalafil should I watch out for low blood pressure?
The blood-pressure-lowering effect is most noticeable in the first few hours after taking tadalafil, but because tadalafil can stay in your system for up to 36 hours, caution is needed throughout this period.
Do I need to stop hydralazine before starting tadalafil?
No—never stop or change your prescribed blood-pressure medicine without advice from your doctor. Your prescriber will assess whether tadalafil can be added safely to your current treatment.
Can I get tadalafil from Cured Pharmacy if I take hydralazine?
Yes, if clinically appropriate. Every order requires an online consultation reviewed by a UK-registered prescriber, who will check your full medical history and current medicines, including hydralazine, before approving treatment.
Medically reviewed by
Tarun Kumar, Superintendent Pharmacist (GPhC 2233073)