Vardenafil: what it treats, how to take it, side effects
Last updated September 3, 2026.
Vardenafil (brand name Levitra, now mostly generic) is a prescription pill for erectile dysfunction. It is a PDE5 inhibitor, the same family as sildenafil (Viagra), taken as needed about an hour before sexual activity.
What does it treat?
It treats erectile dysfunction in adult men: difficulty getting or keeping an erection firm enough for sex. It improves the blood-flow response to sexual stimulation, so it only works when you are actually aroused. It does not raise desire, does not cure the cause of ED, and does not protect against sexually transmitted infections.
How do you take it?
The usual starting dose is 10 mg by mouth about 60 minutes before sexual activity, adjusted by your doctor between 5 mg and 20 mg, and never more than once a day. It works with or without food, though a high-fat meal can blunt the effect. Sexual stimulation is required; the tablet alone does nothing. On certain interacting medicines, the allowed dose drops sharply (for example, no more than 2.5 mg with strong CYP3A4 inhibitors like ketoconazole 400 mg), which is why your prescriber needs your full medication list. Grapefruit and grapefruit juice are also on the discuss-with-your-doctor list.
Side effects to know
- Common: headache, flushing, stuffy or runny nose, upset stomach, heartburn, and dizziness.
- Serious: a dangerous blood-pressure crash with nitrates, an erection lasting more than 4 hours (priapism), sudden vision loss in one eye (NAION), sudden hearing loss, and QT-related heart rhythm effects in susceptible patients.
Who should not take it?
Never combine vardenafil with nitrates in any form (nitroglycerin tablets, sprays, patches, isosorbide) or with riociguat; the combination can drop blood pressure to dangerous levels. That includes the recreational drug "poppers" (amyl nitrite). Caution applies with heart disease, recent heart attack or stroke, very low or uncontrolled high blood pressure, inherited retinal disease, and QT prolongation or the medicines that cause it. Alpha-blockers for prostate or blood pressure need dose coordination. It is not for women or children.
When is it an emergency?
Call 911 for chest pain after taking it (and tell responders you took a PDE5 inhibitor, because nitroglycerin may be off the table), an erection lasting over 4 hours, sudden vision or hearing loss, or fainting. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
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Common questions
Vardenafil vs Viagra: what is the actual difference?
Both are PDE5 inhibitors with similar effectiveness. Vardenafil kicks in at a median of about 60 minutes and lasts roughly 4 to 5 hours, similar to sildenafil. The practical differences are individual: side-effect profile, cost as generics, and how each interacts with your other medicines. Some men respond better to one than the other.
Why can't I take vardenafil with nitroglycerin?
Both dilate blood vessels, and together they can crash blood pressure to dangerous, even fatal, levels. The rule covers every nitrate form: sprays, patches, pastes, isosorbide pills, and recreational "poppers." If you take a PDE5 inhibitor and later need emergency cardiac care, tell the team what you took and when.
Does vardenafil work without sexual stimulation?
No. It amplifies the natural blood-flow response that sexual arousal starts. Taking a tablet and waiting on the couch accomplishes nothing; arousal is the on-switch, the drug just removes a bottleneck.
Can I drink alcohol with vardenafil?
Modest amounts are generally tolerated, but alcohol itself worsens erections and adds to the blood-pressure-lowering and dizziness effects. Heavy drinking with any ED drug is a bad combination both for safety and for the outcome you are taking it for.
Is it safe to buy vardenafil online without a prescription?
That is where counterfeit pills live. ED drugs are among the most faked medications sold online, with wrong doses and wrong ingredients. The safe path is a prescription filled at a licensed pharmacy, and legitimate telehealth services do prescribe ED medication after a real evaluation.
What if 10 mg does not work?
Tell your doctor rather than doubling up. The dose can be adjusted between 5 mg and 20 mg, and several attempts on different days are fair before judging, since anxiety and timing both affect results. If the top dose still fails, that is a reason to look for underlying causes like low testosterone, diabetes, or circulation problems.