Please note: This information was current at the time of publication but now may be out of date. This handout provides a general overview and may not apply to everyone. 

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Am Fam Physician. 1999;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.

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