Please note: This information was current at the time of publication. But medical information is always changing, and some information given here may be out of date. For regularly updated information on a variety of health topics, please visit, the AAFP patient education website.

Information from Your Family Doctor

Using Viagra


Am Fam Physician. 1999 Sep 15;60(4):1172.

  See related article on erectile dysfunction.

What is Viagra?

Viagra is the brand name for sildenafil. It's a medicine that helps men with erectile dysfunction have sex again.

What is erectile dysfunction?

Erectile dysfunction is the inability of the penis to become rigid, or to stay rigid long enough to complete the sex act.

How should I take Viagra?

Take one tablet one hour before you plan to have sex. Don't take more than one tablet in 24 hours. The medicine comes in tablets of 25 mg, 50 mg and 100 mg. Most patients start with 50 mg.

Even if you take Viagra, you still need physical and mental stimulation and desire to have an erection. If your first dose of Viagra doesn't help, call your doctor. Your doctor may want to change your tablet size.

What are the side effects of Viagra?

Viagra has some common side effects:

  • Headache

  • Flushing (face and upper body turning red and warm)

  • Stomach upset

  • Runny nose (sniffles)

  • Vision changes (things look blue)

Headache is the most common side effect. Vision changes are the least common. Talk to your doctor if you have any side effect that bothers you.

Can everyone use Viagra?

You shouldn't use Viagra if you take any of these forms of nitroglycerin or any other nitrates:

  • Isosorbide mononitrate (brand names: Ismo, Monoket, Imdur)

  • Isosorbide dinitrate (brand names: Isordil, Sorbitrate)

  • Sublingual nitroglycerin tablets or spray (brand names: Nitrostat, Nitrolingual Spray)

  • Transdermal nitroglycerin patches or paste (brand names: Minitran, Nitro-Dur, Transderm-Nitro TTS)

If you use Viagra and get chest pains, be sure to tell the paramedics, nurses or doctors at the hospital how long ago it was that you last took Viagra.

This handout is provided to you by your family doctor and the American Academy of Family Physicians. Other health-related information is available from the AAFP online at

This information provides a general overview and may not apply to everyone. Talk to your family doctor to find out if this information applies to you and to get more information on this subject.


Copyright © 1999 by the American Academy of Family Physicians.
This content is owned by the AAFP. A person viewing it online may make one printout of the material and may use that printout only for his or her personal, non-commercial reference. This material may not otherwise be downloaded, copied, printed, stored, transmitted or reproduced in any medium, whether now known or later invented, except as authorized in writing by the AAFP. Contact for copyright questions and/or permission requests.

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