Vardenafil and Terazosin: Can They Be Taken Together?

Vardenafil and Terazosin: Understanding the Interaction

Published: 4 November 2026

Vardenafil and terazosin can be taken together, but only under careful medical supervision because both medicines lower blood pressure and the combination increases the risk of dizziness or fainting. Terazosin is an alpha-blocker used to treat high blood pressure or an enlarged prostate, while vardenafil is a PDE5 inhibitor used for erectile dysfunction. If you're already stable on terazosin, your prescriber will typically start you on the lowest dose of vardenafil and monitor you closely to ensure the combination is safe for you.

What Is Vardenafil and How Does It Work?

Vardenafil (also known by the brand name Levitra) is a prescription medicine used to treat erectile dysfunction in men [5]. 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. This increased blood flow helps you get and maintain an erection suitable for sexual activity.

Vardenafil is available in 5mg, 10mg, and 20mg tablets and is usually taken about 25 to 60 minutes before sexual activity [5]. The medicine only works when you are sexually stimulated—it does not cause an automatic erection. The effect can last for several hours, but you should not take more than one dose in a 24-hour period. Like all PDE5 inhibitors, vardenafil also has a mild blood-pressure-lowering effect, which is important when considering interactions with other medicines.

Common side effects of vardenafil include headache, flushing, indigestion, nasal congestion, and dizziness [5]. Most side effects are mild and short-lived, but the dizziness can be more pronounced if you are also taking medicines that lower blood pressure, such as terazosin.

What Is Terazosin and Why Is It Prescribed?

Terazosin is an alpha-blocker medicine prescribed to treat two main conditions: high blood pressure (hypertension) and the symptoms of an enlarged prostate gland (benign prostatic hyperplasia or BPH). It works by relaxing the smooth muscle in blood vessel walls and in the prostate and bladder neck, which lowers blood pressure and makes it easier to pass urine.

Alpha-blockers like terazosin are effective treatments, but they can cause side effects related to their blood-pressure-lowering action, particularly dizziness or light-headedness when you stand up quickly (called postural hypotension). This effect is usually most noticeable when you first start taking terazosin or when the dose is increased. Your doctor will often start you on a low dose at bedtime and gradually increase it to minimise these side effects.

Because terazosin lowers blood pressure, combining it with other medicines that have the same effect—including vardenafil—requires careful consideration. The risk is that the blood-pressure-lowering effects can add together, leading to excessive drops in blood pressure that cause dizziness, fainting, or falls. This is why your prescriber needs to know about all your current medicines before prescribing vardenafil.

How Do Vardenafil and Terazosin Interact?

The interaction between vardenafil and terazosin occurs because both medicines lower blood pressure, though they do so through different mechanisms. When taken together, their blood-pressure-lowering effects can add up, increasing the risk of symptomatic hypotension—a drop in blood pressure that causes noticeable symptoms such as dizziness, light-headedness, fainting, or feeling weak, particularly when standing up [5].

Vardenafil relaxes blood vessels throughout the body as part of its action, which causes a mild reduction in blood pressure. Terazosin, as an alpha-blocker, also relaxes blood vessels to lower blood pressure and improve urine flow. When you take both medicines, the combined effect on your blood vessels can be greater than either medicine alone, especially in the first few hours after taking vardenafil.

This interaction is well recognised and does not mean the combination is unsafe for everyone—many men take alpha-blockers and PDE5 inhibitors together successfully [2][5]. However, it does mean that your prescriber must assess your individual situation carefully, ensure you are stable on your terazosin dose, and usually start you on the lowest dose of vardenafil (typically 5mg). You should also be aware of the warning signs of low blood pressure and know what to do if they occur.

Why Timing and Dose Matter

The timing of when you take each medicine can influence the interaction. Terazosin is usually taken once daily, often at bedtime to minimise dizziness. Vardenafil is taken on demand, 25 to 60 minutes before sexual activity. If you take vardenafil several hours after your terazosin dose, the peak blood-pressure-lowering effects may not coincide as much, potentially reducing the risk of symptomatic hypotension.

Starting on the lowest dose of vardenafil (5mg) is the standard approach when you are taking an alpha-blocker [5]. Your prescriber may increase the dose only if the lower dose is well tolerated and not fully effective. Never increase the dose yourself or take vardenafil more frequently than prescribed, as this increases the risk of side effects and interactions.

What Your Prescriber Will Check Before Prescribing Vardenafil and Terazosin Together

Before prescribing vardenafil to someone taking terazosin, a UK prescriber will conduct a thorough assessment to ensure the combination is safe for you. They will ask about your current dose of terazosin, how long you have been taking it, and whether you have experienced any side effects such as dizziness or fainting. It is important that you are stable on your alpha-blocker before starting a PDE5 inhibitor [2][5].

Your prescriber will also review your blood pressure readings and ask about any history of low blood pressure or symptoms such as dizziness when standing. They will check for other medicines you are taking that might also lower blood pressure, such as other antihypertensives, and assess your overall cardiovascular health. Conditions such as recent heart attack, stroke, unstable angina, or severe heart failure may mean that sexual activity itself is not advisable, regardless of the interaction [2].

The prescriber will also ensure you are not taking any medicines that are absolutely contraindicated with vardenafil, such as nitrates (GTN spray, isosorbide mononitrate), nicorandil, riociguat, or recreational drugs called poppers (amyl or alkyl nitrites). These combinations can cause a dangerous, potentially life-threatening drop in blood pressure and must never be used together [5]. Additionally, potent CYP3A4 inhibitors (such as ritonavir, ketoconazole, or clarithromycin) can raise vardenafil levels significantly; vardenafil is contraindicated or requires dose adjustment with these medicines [5].

Declaring All Your Medicines

It is essential to declare every medicine you take during your consultation, including prescription medicines, over-the-counter products, herbal remedies (such as St John's wort), and recreational drugs. Even medicines you take occasionally or 'as needed' must be mentioned. Your prescriber cannot assess safety accurately without a complete picture of what you are taking.

If you start a new medicine after being prescribed vardenafil, or if your terazosin dose changes, contact your prescriber or pharmacist to check whether your vardenafil dose needs adjusting. Do not stop taking terazosin or any other prescribed medicine without medical advice, as this could worsen your blood pressure or prostate symptoms.

Practical Advice for Taking Vardenafil and Terazosin Safely

If your prescriber has determined that vardenafil and terazosin are safe for you to take together, there are several practical steps you can take to minimise the risk of side effects. First, always start with the lowest prescribed dose of vardenafil (usually 5mg) and do not increase it without consulting your prescriber. Take vardenafil only as needed, about 25 to 60 minutes before sexual activity, and never more than once in 24 hours [5].

Be particularly cautious when standing up, especially in the first few hours after taking vardenafil. Stand up slowly from sitting or lying positions to give your body time to adjust and reduce the risk of dizziness or fainting. Avoid heavy alcohol consumption, as alcohol can worsen erectile dysfunction, add to the blood-pressure-lowering effect, and increase the risk of side effects. Limit yourself to one or two units of alcohol if you plan to take vardenafil.

If you experience dizziness, light-headedness, or feel faint after taking vardenafil, sit or lie down immediately until the symptoms pass. Do not drive or operate machinery if you feel dizzy. If the symptoms are severe, persistent, or you actually faint, seek medical advice promptly. Keep well hydrated, but avoid grapefruit juice, as it can increase vardenafil levels in your blood and raise the risk of side effects [5].

Warning Signs and When to Seek Help with Vardenafil and Terazosin

While most men tolerate the combination of vardenafil and terazosin well when properly prescribed, it is important to recognise warning signs that need urgent attention. If you experience severe dizziness, fainting, or a feeling that you might pass out, stop what you are doing, sit or lie down, and seek medical help if the symptoms do not resolve quickly. Fainting can lead to falls and injury, so take these symptoms seriously.

Seek urgent medical help (call 999 or go to A&E) if you develop chest pain during or after sexual activity, as this could indicate a heart problem. Also seek emergency help if you have an erection that lasts longer than four hours (priapism), even if it is not painful—this is a medical emergency that requires immediate treatment to prevent permanent damage [5]. Sudden loss of vision in one or both eyes, or sudden decrease or loss of hearing (sometimes with ringing in the ears or dizziness), are rare but serious side effects that require immediate medical attention [5].

If you develop new symptoms or side effects after starting vardenafil, or if your existing symptoms worsen, contact your prescriber or pharmacist for advice. Do not simply stop taking either medicine without guidance, as stopping terazosin suddenly could cause your blood pressure to rise or your prostate symptoms to return. Your prescriber can adjust doses, suggest alternative timings, or consider a different ED treatment if needed.

Regular Monitoring and Follow-Up

If you are taking vardenafil and terazosin long-term, regular follow-up with your GP or prescriber is important. They can monitor your blood pressure, review how well the medicines are working, and check for any new interactions if other medicines are added. Erectile dysfunction can sometimes be an early warning sign of cardiovascular disease or diabetes, so ongoing monitoring of your overall health is valuable [1][2].

If vardenafil is not effective or causes troublesome side effects even at the lowest dose, discuss alternatives with your prescriber. Other PDE5 inhibitors such as sildenafil or tadalafil may be better tolerated in combination with terazosin, or non-tablet treatments may be considered. The goal is to find a safe, effective treatment that works for your individual circumstances.

Scientific References

1. NHS. (n.d.). Erectile dysfunction (impotence). NHS website. https://www.nhs.uk/conditions/erection-problems-erectile-dysfunction/ [accessed 4 November 2026]
2. National Institute for Health and Care Excellence. (n.d.). Erectile dysfunction. Clinical Knowledge Summaries. https://cks.nice.org.uk/topics/erectile-dysfunction/ [accessed 4 November 2026]
3. Joint Formulary Committee. (n.d.). Vardenafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/vardenafil/ [accessed 4 November 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.