The information provided here is meant to give you a general idea of what to expect from each of these medications. Only the most common side effects are included, so ask your healthcare provider if there are any precautions specific to your case. Use each of these medications as recommended by your healthcare provider or according to the instructions provided with the medication. If you have further questions about usage or side effects, contact your healthcare provider.

There are three medical treatments available for erectile dysfunction—pills, urethral inserts, and injections.

Prescription Medications


Sildenafil (Viagra)

Viagra was developed to treat heart disease, but during its clinical trials the subjects noticed they were having erections. Viagra works best between one and two hours after taking it. Sexual function improves by a factor of three to four; 4 out of 5 patients taking the drug report improvement. Viagra has been shown to be effective in ED associated with diabetes, spinal cord injury, and SSRIs.

In contrast to the other agents listed below, sildenafil does not produce an erection in the absence of sexual stimulation. It merely enhances the response. Take sildenafil about an hour before planned sexual activity.

Viagra should not be used in the following conditions:

  • Recent heart attack]]> or ]]>stroke]]>
  • Heart failure
  • Concurrent use of nitrate
  • Concurrent use of other medications for erectile dysfunction
  • Hereditary retinal disorders, such as ]]>retinitis pigmentosa]]>

Viagra should be used with caution in the following:

  • Liver or kidney failure
  • Bleeding disorders
  • Ulcer disease
  • Heart disease
  • Concurrent use of blood pressure medicines, especially alpha-blockers
  • The elderly

Viagra must be obtained by prescription. There is important information your doctor needs to know about your health before the medication is prescribed.

Possible side effects include:

  • Headache
  • Flushing
  • Indigestion
  • Visual disturbances, a condition known as nonarteritic anterior ischemic optic neuropathy (NAION) that can cause sudden blindness
  • Drug interactions

Vardanafil (Levitra) and Tadalafil (Cialis)

These newer drugs have the same efficacy, safety profile, and cost effectiveness as Viagra. However, the following are major differences you should be aware of:

  • Food, especially fatty food, can delay the absorption of sildenafil and vardanafil, but not tadalafil.
  • The duration of action of these drugs are different:
    • 4-5 hours for sildenafil and vardanafil
    • Up to 36 hours for tadalafil


There are two types of alprostadil:

  • Transurethral alprostadil (MUSE)
  • Intracavernosal alprostadil (Caverject, Edex)

Alprostadil acts directly on the blood vessels in the penis to cause an erection. It can be inserted into the urethra (urinary tube in the penis) with a special device or injected with a small needle. Erection occurs in 8-10 minutes and lasts 30-60 minutes. The injection is effective in about 65%-85% of users; the insert is effective in about 65%. The maximal number of injections per week is three.

Possible side effects include:

  • Dizziness
  • Low blood pressure
  • Pain in the penis
  • Problems from the injecting needle
  • Prolonged, painful erection (priapism) (0.4% of users)
  • Bleeding in patients on blood thinners

Special Considerations

Whenever you are taking a prescription medication, take the following precautions:

  • Take them as directed—not more, not less, not at a different time.
  • Do not stop taking them without consulting your healthcare provider.
  • Don’t share them with anyone else.
  • Know what effects and side effects to expect, and report them to your healthcare provider.
  • If you are taking more than one drug, even if it is over-the-counter, be sure to check with a physician or pharmacist about drug interactions.
  • Plan ahead for refills so you don’t run out.

When to Contact Your Healthcare Provider

Contact your healthcare provider if any of the following occur:

  • A side effect that troubles you
  • Priapism (prolonged, painful erection)—This condition can be dangerous. If four hours have passed and your penis still hasn't relaxed, seek emergency medical care.