Vardenafil is sold under its generic name and the brand names Levitra and Staxyn. It falls into a group of drugs called phosphodiesterase-5 (PDE5) inhibitors.

PDE5 inhibitors are taken orally to treat erectile dysfunction (ED). They help your blood vessels relax, and allow you to more easily get an erection when sexually stimulated. Studies have found vardenafil to be generally safe and effective for treating erectile dysfunction.

But vardenafil can cause side effects in some people. Side effects are usually mild, but rare symptoms like an erection lasting more than 4 hours need immediate medical attention.

Keep reading to learn about the potential side effects of vardenafil, as well as possible drug interactions.

Vardenafil and other PDE5 inhibitors help you achieve an erection by reducing the action of the enzyme PDE5. This enzyme is found in a high concentration in your penis, but it’s also found in blood vessels throughout your body.

Because PDE5 inhibitors don’t specifically act on your penis, they can cause a wide range of side effects.

The most common short-term side effects of vardenafil reported in clinical trials include:

The only symptoms reported in more than 10 percent of people were headaches (15 percent) and facial flushing (11 percent).

The following side effects are less common but are reported by a small number of people after taking vardenafil:

This isn’t a comprehensive list of all possible symptoms. If you notice anything else concerning after taking vardenafil, it’s a good idea to call a doctor.

Taking more than the recommended dosage of vardenafil can increase your risk of developing mild and serious side effects.

The maximum dose that researchers have evaluated in humans is 120 milligrams at one time in healthy male individuals. At this daily dose, the majority of study participants experienced either back pain, muscle pain, or abnormal vision. Daily doses up to 40 milligrams have been tolerated for 4 weeks without causing serious side effects.

The recommended starting dose of vardenafil is 10 milligrams taken 1 hour before sexual activity. However, the amount that’s best for you can be higher or lower. A doctor can advise you how much you should take daily.

Vardenafil and other PDE5 inhibitors have the potential to interact with other medications you’re taking. Before you start taking vardenafil, it’s important to talk to a doctor about whether it’s safe for you.

Medications known to interact with vardenafil include:

  • nitrates and nitric oxide donors
  • guanylate cyclase stimulators like riociguat
  • alpha-blockers
  • other medications used to control blood pressure
  • medications that regulate your heartbeat
  • other PDE5 inhibitors
  • HIV protease inhibitors

In some cases, it may be possible to take vardenafil with a modified dose of your current medications. However, in other cases, a doctor may deem it unsafe.

Although Levitra and other forms of vardenafil have the potential to be effective ED treatments, it’s important to discuss your medical history with a doctor before taking it. Vardenafil isn’t a suitable treatment option for some groups of people.

If you have a heart condition that could be made worse by sexual activity, you should avoid vardenafil. Some heart conditions that exclude you from being able to safely take vardenafil include:

People with hereditary degenerative retinal disorders, liver failure, or who are on renal dialysis should also avoid vardenafil because of a lack of long-term research.

Vardenafil isn’t approved by the FDA to treat any conditions in women.

If you experience an erection that lasts more than 4 hours, seek medical assistance as soon as possible. A prolonged erection is called priapism and can lead to permanent damage to your penis if not treated immediately.

If you notice a sudden decrease or loss in your hearing you should also contact a doctor immediately. Often, hearing loss is paired with dizziness and a ringing in your ear.

Vision loss in one or both eyes is another emergency symptom that requires prompt attention. It can be a sign of a serious condition affecting your optic nerve, called non-arteritic anterior ischemic optic neuropathy.

It’s a good idea to contact a doctor as soon as possible if you notice anything else concerning you.

Vardenafil is generally safe, and serious side effects are uncommon. But in rare cases, vardenafil can contribute to conditions that require a doctor’s attention.

If you experience vision loss, hearing loss, or an erection that lasts more than 4 hours, it’s important to seek medical attention right away.