Erectile dysfunction: Viagra and other oral medications

Oral medications are often the first line of treatment 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, Staxyn), tadalafil (Cialis) and avanafil (Stendra) are oral medications that reverse erectile dysfunction by enhancing the effects of nitric oxide, a natural chemical your body produces that relaxes muscles in the penis. This increases blood flow and allows you to get an erection in response to sexual stimulation.

How oral medications differ

Although they work in similar ways, each oral medication 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 as well as any health problems you have and possible interactions with other medications you take.

• Sildenafil (Viagra). This medication is most effective when taken on an empty stomach one hour before sex. It's effective for up to six hours.
• Vardenafil (Levitra, Staxyn). This medication also is most effective when taken one hour before sex and can be taken with or without food. It's effective for up to seven hours.
• Tadalafil (Cialis). This medication is taken with or without food about one to two hours before sex. It's effective for 36 hours. It can be taken in a small dose daily or in a larger dose as needed.
• Avanafil (Stendra). This medication is taken with or without food 15 to 30 minutes before sex, depending on the dose. It lasts up to six hours.

When oral medications might not be safe

Before taking any medication for erectile dysfunction, get your doctor's OK. Medications for erectile dysfunction might not work or might be dangerous if you:

• Take nitrate drugs — commonly prescribed for chest pain (angina) — such as nitroglycerin (Minitran, Nitro-Dur, Nitrostat, others), isosorbide mononitrate (Monoket) and isosorbide dinitrate (Dilatrate-SR, Isordil)
• Have very low blood pressure (hypotension) or uncontrolled high blood pressure (hypertension)
• Have severe liver disease
• Have kidney disease that requires dialysis

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