Vardenafil Side Effects: What to Expect and When to Call Your Doctor

If your doctor has prescribed vardenafil (brand names Levitra and Staxyn) for erectile dysfunction, it helps to know what to expect before your first dose. Vardenafil side effects are generally predictable — headache, flushing, and a stuffy nose are the most common — but the issue that matters most is the strict contraindication against combining it with nitrate medications, which can cause a dangerous, potentially fatal drop in blood pressure. Here’s a clear look at what the evidence shows, including the interactions worth knowing about if you’re already taking a blood pressure medication for an enlarged prostate.

How Vardenafil Works

Vardenafil belongs to a class of medications called PDE5 inhibitors, the same category as sildenafil and tadalafil. It works by blocking an enzyme called phosphodiesterase type 5, which allows blood vessels in the penis to relax and fill with blood in response to sexual stimulation, producing and sustaining an erection. Vardenafil doesn’t cause an erection on its own — sexual stimulation is still required — and it doesn’t increase sexual desire. Because PDE5 inhibitors relax blood vessels throughout the body to some degree, not just in the penis, that same mechanism is what’s behind both the flushing and headache side effects and the more serious blood-pressure interactions with nitrates and alpha-blockers.

Common Side Effects

Based on FDA prescribing information from placebo-controlled clinical trials (placebo n=1,199; vardenafil n=2,203, across the 5, 10, and 20 mg doses), here’s how vardenafil’s side effect rates compared to placebo:

• Headache. About 15% on vardenafil versus 4% on placebo — the single most commonly reported side effect.
• Flushing. About 11% versus 1% on placebo, from the same vessel-dilating effect that helps treat ED.
• Nasal congestion or rhinitis. About 9% versus 3% on placebo — a stuffy or runny nose.
• Indigestion (dyspepsia). About 4% versus 1% on placebo.
• Dizziness. Reported commonly, though at a lower rate than headache or flushing.
• Back pain and muscle aches. Reported in clinical data, generally mild and temporary.

Most of these effects are mild to moderate and tend to resolve on their own without needing to stop the medication. They’re also dose-related to some degree, meaning a lower dose may cause fewer or milder side effects if the higher dose isn’t necessary for an adequate response.

The Nitrate Interaction: An Absolute Contraindication

This is the single most important safety rule for anyone taking vardenafil. The FDA label states plainly that administering vardenafil with nitrates — whether taken regularly or only occasionally — is contraindicated, and that no safe time interval between the two has been established. Nitrate medications include nitroglycerin and isosorbide, commonly prescribed for angina (chest pain related to heart disease), as well as recreational “poppers” that contain amyl or butyl nitrate. Combining either with vardenafil can cause a severe, unpredictable drop in blood pressure that can be life-threatening. If you have heart disease and are ever prescribed a nitrate medication for chest pain — including in an emergency room, where this history might not be immediately on hand — it’s critical that the treating doctor knows you’ve taken vardenafil and roughly when, since there’s no established safe gap between the two.

The Alpha-Blocker Interaction

Many men managing an enlarged prostate (BPH) take an alpha-blocker such as tamsulosin, doxazosin, or terazosin, all of which also lower blood pressure to varying degrees. Because vardenafil can further lower blood pressure, combining it with an alpha-blocker can lead to symptomatic hypotension — dizziness, lightheadedness, or fainting, especially when standing up. The FDA label recommends starting at the lowest vardenafil dose in patients already stable on alpha-blocker therapy, and suggests considering some time interval between doses, though it doesn’t specify an exact number of hours. If you’re prescribed both a PDE5 inhibitor and an alpha-blocker, your doctor will typically want you established and stable on one before starting the other, and may recommend monitoring for lightheadedness as you adjust.

Vision and Hearing Changes: A Rare but Real Concern

PDE5 inhibitors as a class, including vardenafil, have been associated with rare but serious reports of sudden vision loss (including a condition called non-arteritic anterior ischemic optic neuropathy, or NAION) and sudden hearing loss, sometimes accompanied by dizziness and ringing in the ears. These events are uncommon, and it isn’t entirely clear whether the medication directly causes them or whether they occur in people who already had underlying risk factors for these conditions, such as certain eye or cardiovascular conditions. Even so, because the onset can be sudden and the window for effective treatment of some causes of vision loss is narrow, any sudden change in vision or hearing after taking vardenafil warrants stopping the medication and seeking prompt medical evaluation rather than waiting to see if it passes on its own.

Serious Side Effects That Need Prompt Attention

• An erection lasting 4 hours or longer (priapism). This is a medical emergency that can cause permanent damage if not treated promptly.
• Sudden vision loss or changes. A sudden decrease or loss of vision in one or both eyes needs immediate medical attention.
• Sudden hearing loss. Especially if accompanied by dizziness or ringing in the ears, this needs prompt evaluation.
• Chest pain, irregular heartbeat, or shortness of breath. These warrant emergency evaluation, particularly in anyone with existing heart disease.
• A severe allergic reaction. Swelling of the face, lips, tongue, or throat, or difficulty breathing, requires emergency care.
• Fainting or a significant, sudden blood pressure drop. Especially when combined with a nitrate or alpha-blocker.

Who Should Use Extra Caution

• Anyone taking any form of nitrate medication. This combination is contraindicated outright, not just a caution.
• Anyone taking an alpha-blocker for BPH or blood pressure. Dose adjustments or timing considerations may be needed.
• Anyone with a history of heart disease, recent heart attack, or stroke. Sexual activity itself carries some cardiovascular demand, and this should be discussed with a doctor before starting any ED medication.
• Anyone with a personal or family history of QT prolongation, or taking Class IA or Class III antiarrhythmic medications. These should generally avoid vardenafil due to an additive effect on heart rhythm.
• Anyone with significant liver or kidney impairment. Dose adjustments may be needed, since these organs affect how the medication is processed and cleared.

Vardenafil Compared to Other ED Medications

Vardenafil is one of several PDE5 inhibitors used for erectile dysfunction, alongside sildenafil (Viagra) and tadalafil (Cialis). All three share the same core mechanism and the same absolute nitrate contraindication, but they differ in how quickly they take effect and how long they last. Vardenafil generally takes effect within about 30 to 60 minutes and lasts several hours, similar to sildenafil, while tadalafil is notable for a much longer window of effectiveness, up to 36 hours, which is part of why some men and their doctors prefer it for spontaneity rather than timed dosing. Vardenafil’s QT-prolongation caution is somewhat more specific in its labeling than sildenafil’s or tadalafil’s, which is relevant mainly for people already taking certain heart rhythm medications. For a broader look at erectile dysfunction and its many underlying causes beyond medication choice, see this site’s overview of erectile dysfunction causes.

What to Expect When Starting Vardenafil

Vardenafil is typically prescribed on an as-needed basis, taken roughly 25 to 60 minutes before sexual activity, rather than as a daily medication. A high-fat meal can delay how quickly it’s absorbed, so taking it on an emptier stomach tends to make the onset more predictable. It’s common for a doctor to start at a middle dose and adjust up or down after a few attempts, based on how well it worked and how much side effects like headache or flushing bothered you. Because side effects like flushing and headache are tied to the dose, finding the lowest effective dose for you specifically — rather than defaulting to the highest one — often strikes the best balance between reliable effectiveness and tolerability. If three or four attempts at a given dose, with adequate sexual stimulation, don’t produce a satisfactory result, that’s worth discussing with your doctor rather than assuming the medication simply doesn’t work for you.

Tips for Taking Vardenafil Safely

• Never combine it with nitrate medications, in any form, at any interval. This is the one absolute rule.
• Tell every doctor you see that you take vardenafil, especially before any emergency chest pain treatment. This can be lifesaving information if nitrates are being considered.
• If you also take an alpha-blocker, confirm the timing and dose with your doctor. Don’t assume it’s fine to combine them without guidance.
• Avoid a heavy, high-fat meal right before taking it. This can delay how quickly it starts working.
• Limit alcohol when taking vardenafil. Alcohol can worsen dizziness and blood-pressure-related side effects.
• Seek care immediately for an erection lasting 4 hours or more. Waiting can lead to permanent damage.

When to Call Your Doctor

Contact your doctor if headache, flushing, or congestion is bothersome or doesn’t improve, or if the medication doesn’t seem to be working after several attempts with adequate stimulation. Seek emergency care immediately for an erection lasting 4 hours or longer, sudden vision or hearing changes, chest pain, or a severe allergic reaction.

Frequently Asked Questions

Can I drink alcohol while taking vardenafil?

In moderation, it’s generally considered acceptable, but heavy drinking can increase dizziness and blood-pressure-related side effects, and can also affect your ability to achieve an erection on its own.

How long does vardenafil last?

Its effects generally last several hours, with onset around 30 to 60 minutes after taking it. This is shorter than tadalafil, which can remain effective for up to 36 hours.

Why can’t I take vardenafil with nitrates?

Both relax blood vessels, and combining them can cause a severe, potentially life-threatening drop in blood pressure. The FDA label describes this as an absolute contraindication with no established safe time gap.

I take tamsulosin for my prostate — can I also take vardenafil?

Possibly, but it requires caution and your doctor’s guidance, since both can lower blood pressure and the combination raises the risk of dizziness or fainting. Your doctor will likely want you stable on one before starting the other.

What should I do if an erection doesn’t go away?

Seek emergency medical care if it lasts 4 hours or longer. This is a true medical emergency (priapism) that can cause lasting damage if not treated promptly.

This article is for general educational purposes and isn’t a substitute for personalized medical advice. Never start, stop, or change a prescription medication without talking to your doctor first.

Vardenafil’s everyday side effects — headache, flushing, a stuffy nose — are common but generally mild and manageable, often improving once you’ve found the right dose for you. The real safety story is the absolute nitrate contraindication and the need for caution if you’re also taking an alpha-blocker for an enlarged prostate. Being upfront with every doctor you see about taking vardenafil, especially in any situation where a nitrate might be considered, is the single most important safety habit to carry forward.