Tadalafil and Indoramin: Can You Take Them Together?
Learn how these medicines interact and what your prescriber checks during a UK pharmacist-led consultation.
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Tadalafil and Indoramin: Understanding the Interaction
Published: 22 October 2026
Many men wonder whether tadalafil and indoramin can be taken together safely. The short answer is yes, but only under careful medical supervision, because both medicines can lower blood pressure and the combination may increase the risk of dizziness or fainting. Indoramin is an alpha-blocker used to treat high blood pressure or urinary symptoms from an enlarged prostate, while tadalafil is a PDE5 inhibitor used for erectile dysfunction. Your prescriber will check that you are stable on indoramin and will usually start you on the lowest dose of tadalafil to minimise the risk of a sudden drop in blood pressure.
Take it slowly
When you first start tadalafil while on indoramin, sit on the edge of the bed for a moment before standing up in the morning. This simple step can help prevent dizziness and reduce the risk of falls.
What is tadalafil and how does it work?
Tadalafil is a prescription medicine used to treat erectile dysfunction (ED) in men. 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 on its own—you still need sexual stimulation for it to work [3][4].
Tadalafil is available in two forms: on-demand tablets (usually 10 mg or 20 mg) taken at least 30 minutes before sex, with effects lasting up to 36 hours, and daily low-dose tablets (2.5 mg or 5 mg) taken once a day to allow for more spontaneity. Because tadalafil can also relax blood vessels elsewhere in the body, it has a mild blood-pressure-lowering effect, which is why interactions with other blood-pressure medicines need to be carefully managed [4].
At Cured Pharmacy, tadalafil is available after an online consultation reviewed by a UK-registered prescriber. Generic tadalafil starts from £7.95, or £6.36 for your first order with code Ednew. Branded Cialis is also available at £12.00 (£9.60 with code Ednew).
What is indoramin and why is it prescribed?
Indoramin is an alpha-blocker, a type of medicine that relaxes certain muscles in the body. It is most commonly prescribed to treat high blood pressure (hypertension) or to relieve urinary symptoms caused by an enlarged prostate gland (benign prostatic hyperplasia, or BPH). Indoramin works by blocking alpha-1 receptors in the smooth muscle of blood vessels and the prostate, causing them to relax [12].
When blood vessels relax, blood pressure falls, which is helpful for managing hypertension. In the prostate and bladder neck, relaxation of the muscle makes it easier to pass urine. However, because indoramin lowers blood pressure, it can cause side effects such as dizziness, light-headedness (especially when standing up quickly), and tiredness, particularly when you first start taking it or if the dose is increased [12].
Other alpha-blockers you may have heard of include doxazosin, tamsulosin, alfuzosin, terazosin, prazosin, and silodosin. All of these medicines work in a similar way and share the same potential interaction with tadalafil and other PDE5 inhibitors.
When to get urgent help
- Erection lasting longer 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; tell paramedics you have taken tadalafil (do not use GTN)
- Severe dizziness, fainting, or feeling faint when standing – sit or lie down and seek medical advice
- Swelling of face, lips, or tongue, or difficulty breathing – stop tadalafil and call 999 or 111
Call 999 or go to A&E in an emergency, or contact NHS 111 for urgent advice.
How do tadalafil and indoramin interact?
The interaction between tadalafil and indoramin is pharmacodynamic, meaning both medicines have an effect on blood pressure and those effects can add together. Tadalafil relaxes blood vessels in the penis and also has a mild effect on blood vessels throughout the body, which can lower blood pressure slightly. Indoramin also lowers blood pressure by relaxing blood vessels. When you take both medicines together, the combined effect on blood pressure can be greater than either medicine alone [3][4][12].
This does not mean the combination is unsafe, but it does mean there is an increased risk of symptoms such as dizziness, light-headedness, or fainting, especially when you stand up quickly (a condition called postural or orthostatic hypotension). In most men who are already stable on indoramin, the risk can be managed by starting tadalafil at the lowest effective dose and monitoring how you feel [3][4].
It is important to note that this interaction applies to all PDE5 inhibitors (sildenafil, tadalafil, vardenafil, and avanafil) and all alpha-blockers. Your prescriber will take a full medication history during your consultation to check for this and other interactions, and will only prescribe tadalafil if it is safe and appropriate for you.
Why the interaction matters
A sudden drop in blood pressure can make you feel dizzy, weak, or cause you to faint, which can be dangerous, especially if you are driving, operating machinery, or standing on stairs. The risk is highest when you first start tadalafil, when your dose is increased, or if you take tadalafil and indoramin close together in time. Your prescriber will give you specific advice on timing and dosing to minimise this risk [3][4][12].
What will your prescriber check before prescribing tadalafil and indoramin together?
Before prescribing tadalafil to someone taking indoramin, a UK prescriber will carry out a thorough assessment. They will ask about your current dose of indoramin, how long you have been taking it, and whether your blood pressure is well controlled and stable. It is important that you are already established on a stable dose of the alpha-blocker before starting a PDE5 inhibitor, as this reduces the risk of a sudden blood-pressure drop [2][3][4].
Your prescriber will also ask about any symptoms of low blood pressure you may already experience, such as dizziness when standing up, and will check for other medicines or health conditions that might increase the risk. They 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 and some conditions make PDE5 inhibitors unsuitable [2][3].
If tadalafil is appropriate, your prescriber will usually start you on the lowest dose (often 10 mg on-demand, or 2.5 mg daily) and advise you to take it at a time when you are not also taking your indoramin dose, if possible, to spread out the blood-pressure-lowering effects. They will also give you clear advice on warning signs to watch for and when to seek help [3][4].
Declaring all your medicines
It is essential to tell your prescriber about every medicine you take, including over-the-counter medicines, herbal remedies (such as St John's wort), and recreational drugs. Some medicines can interact dangerously with tadalafil—for example, nitrates (GTN spray, isosorbide mononitrate), nicorandil, riociguat, and poppers (amyl or alkyl nitrites) must never be taken with tadalafil, as the combination can cause a life-threatening drop in blood pressure [3][4].
At a glance
Practical advice for taking tadalafil and indoramin safely
If your prescriber has approved tadalafil while you are taking indoramin, follow their instructions carefully. 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). If you are on daily tadalafil, take it at the same time each day. Try to avoid taking both medicines at exactly the same time; your prescriber may suggest spacing them out during the day [3][4].
Be cautious when you first start tadalafil or if your dose is increased. Avoid sudden changes in posture—for example, sit on the edge of the bed for a moment before standing up in the morning. If you feel dizzy or light-headed, sit or lie down until the feeling passes. Avoid heavy alcohol, as it can make dizziness worse and may also make it harder to get an erection [3][4].
Do not drive or operate machinery if you feel dizzy or unwell. If you experience chest pain during or after sex, do not take nitrate medicines (such as GTN spray) without telling the doctor or paramedic that you have taken tadalafil, as the combination is dangerous. Keep a list of all your medicines with you, or use the NHS app to share your medication record with healthcare professionals [3][4].
Warning signs and when to seek help with tadalafil and indoramin
Most men taking tadalafil and indoramin together do not experience serious 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 to the penis. Sudden loss of vision in one or both eyes, or sudden decrease or loss of hearing (sometimes with ringing in the ears or dizziness), requires urgent medical assessment—stop taking tadalafil and seek help straight away [3][4].
If you experience severe dizziness, fainting, or feel like you are about to faint, especially when standing up, sit or lie down and seek medical advice. If you develop chest pain, shortness of breath, or an irregular heartbeat during or after sexual activity, call 999 and tell the paramedics you have taken tadalafil—do not use GTN or other nitrate medicines [3][4].
Less urgent but still important: if you develop a rash, swelling of the face, lips, or tongue, or difficulty breathing, stop taking tadalafil and contact your GP or call 111, as these may be signs of an allergic reaction. If tadalafil does not work for you, or if you experience troublesome side effects such as headache, indigestion, back pain, or muscle aches, speak to your prescriber—they may adjust your dose or suggest an alternative treatment [3][4].
Ongoing monitoring
Your GP or prescriber may want to review your blood pressure and overall health periodically, especially if you are taking multiple medicines that affect blood pressure. Do not stop taking indoramin or tadalafil, or change the dose, without discussing it with your prescriber first. If you start any new medicine, including over-the-counter or herbal products, check with your pharmacist or prescriber whether it is safe to take with tadalafil [3][4][12].
In summary
- Tadalafil and indoramin can be taken together, but only under medical supervision and at the lowest effective dose.
- Both medicines lower blood pressure, so the combination may increase the risk of dizziness or fainting.
- You must be stable on indoramin before starting tadalafil, and your prescriber will assess your suitability carefully.
- Watch for warning signs such as severe dizziness, fainting, chest pain, or an erection lasting over four hours.
- Always declare all your medicines during your consultation, including over-the-counter and herbal products.
Scientific References
- National Institute for Health and Care Excellence. (n.d.). Erectile dysfunction. Clinical Knowledge Summaries. https://cks.nice.org.uk/topics/erectile-dysfunction/ [accessed 22 October 2026]
- Joint Formulary Committee. (n.d.). Sildenafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/sildenafil/ [accessed 22 October 2026]
- Joint Formulary Committee. (n.d.). Tadalafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/tadalafil/ [accessed 22 October 2026]
- Electronic Medicines Compendium. (n.d.). Summaries of Product Characteristics and Patient Information Leaflets. https://www.medicines.org.uk/emc/ [accessed 22 October 2026]
- NHS. (n.d.). Erectile dysfunction (impotence). https://www.nhs.uk/conditions/erection-problems-erectile-dysfunction/ Accessed 22 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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