Erectile dysfunction: Viagra and other oral medications

By Mayo Clinic Staff

Viagra, Levitra or Cialis is often the first oral medication tried for erectile dysfunction. For most men who have trouble keeping an erection firm enough for sex (erectile dysfunction), these medications work well and cause few side effects.

Sildenafil (Viagra), vardenafil (Levitra or Staxyn) and tadalafil (Cialis) are all medications that reverse erectile dysfunction by increasing nitric oxide, a chemical naturally produced by your body. Nitric oxide opens and relaxes blood vessels in the penis, helping you get and keep an erection. These erectile dysfunction medications don't increase your sex drive and only cause erections when you are sexually stimulated.

Viagra, Levitra and Cialis — How they're different

Although they work in similar ways, each of these medications has a slightly different chemical makeup. These minor differences affect the way each medication works, such as how quickly it takes effect and wears off, and the potential side effects. Your doctor will consider these factors when deciding if one of these medications is a good choice for you. Your doctor will also consider any health problems you have and possible interactions with other medications you take.

 Viagra, LevitraCialis (small dose daily)Cialis (36-hour)
How to take it Without food, no more than once a day With or without food, once a day With or without food, no more than once a day
When to take it About 30-60 minutes before sex Anytime About 30 minutes before sex
How long it's effective Up to 5 hours Anytime between doses Up to 36 hours

Vardenafil (Levitra) can also be prescribed in a tablet that dissolves on the tongue (Staxyn).

A new medication, avanafil (Stendra), was approved in April 2012 by the Food and Drug Administration for treating erectile dysfunction. Stendra works similarly to Viagra, Levitra and Cialis.

When these medications may not be safe

Not all men can safely take erectile dysfunction medications. They can be dangerous if you have certain health problems or you're taking particular medications. Erectile dysfunction medications may not be safe if you have:

  • Heart problems, including reduced blood flow (aortic stenosis or left ventricular outflow obstruction), heart pain (angina), abnormal heart rhythms (arrhythmia) or a recent heart attack
  • High or low blood pressure that isn't controlled
  • A history of stroke within the last six months
  • Eye problems, such as retinitis pigmentosa, or if you have a family history of certain eye problems
  • Severe liver disease, including cirrhosis
  • Kidney disease that requires dialysis

Never take Viagra, Levitra or Cialis if you take nitrate drugs to treat heart pain (angina). Like Viagra, Levitra and Cialis, nitrate drugs dilate blood vessels. Their combined effects can cause dangerously low blood pressure and loss of consciousness. Medications that contain nitrates include:

  • Nitroglycerin (Nitro-Bid, Minitran, others)
  • Isosorbide (Dilatrate-SR, Isordil, Monoket, others)
  • Illegal drugs such as amyl nitrite or "poppers"

Tell your doctor about any medications you're taking. A number of other drugs can also interact with Viagra, Levitra or Cialis. They include:

  • Alpha blockers
  • Antibiotics
  • Anti-seizure medications
  • Blood thinners
  • Anti-arrhythmic heart medications

Side effects

Most men who take Viagra, Levitra and Cialis aren't bothered by side effects. When side effects do occur, they can include:

  • Headache
  • Flushing (with Viagra and Levitra)
  • Indigestion
  • Stuffy or runny nose
  • Back pain and muscle aches (with Cialis)
  • Temporary vision changes, including "blue vision" (with Viagra and Levitra)
  • Dizziness or fainting (rare)

In a small number of cases, men taking Viagra, Levitra or Cialis have reported more serious side effects:

  • Hearing loss or vision loss. Some men have had sudden loss of hearing or loss of vision after taking one of these medications. However, it isn't clear whether vision or hearing loss was directly caused by taking the medication or by a pre-existing condition. If you're taking one of these medications for erectile dysfunction and have sudden loss of hearing or vision, seek medical help right away.
  • An erection that doesn't go away on its own. Called priapism, this rare condition can be painful and requires medical treatment to avoid damage to your penis. If you have an erection that lasts more than four hours, seek medical attention.
Jun. 06, 2012 See more In-depth