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 doctor or according to the instructions provided with the medication. If you have further questions about usage or side effects, contact your doctor.

Erectile dysfunction medications may be in the form of pill, urethral inserts, or injections.

Prescription medications



Sildenafil was developed to treat heart disease, but during its clinical trials the subjects noticed they were having erections. Sildenafil works best 1-2 hours after taking it. It has been shown to be effective in men with diabetes, spinal cord injury, and medications used to treat depression.

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.

Sildenafil should not be used in the following conditions:

Sildenafil should be used with caution in the following:

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

Sildenafil 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


Vardenafil, tadalafil, and avanafil

Newer drugs have the same efficacy, safety profile, and cost effectiveness as sildenafil. However, major differences from sildenafil exist and include:

  • Delayed absorption after eating food, especially fatty food, with sildenafil, vardenafil, and avanafil, but not tadalafil
  • The duration of action:
    • 4-5 hours for sildenafil, vardenafil, and avanafil
    • Up to 36 hours for tadalafil



There are 2 types of alprostadil:

  • Transurethral alprostadil
  • Intracavernosal alprostadil

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 and the insert is effective in about 65%. The maximal number of injections per week is 3.

Possible side effects include:

  • Lightheadedness
  • Low blood pressure
  • Pain in the penis
  • Problems from the injecting needle
  • Prolonged, painful erection—priapism
  • Bleeding in those on blood thinners

Special considerations

If you are taking medications, follow these general guidelines:

  • Take the medication as directed. Do not change the amount or the schedule.
  • Ask what side effects could occur. Report them to your doctor.
  • Talk to your doctor before you stop taking any prescription medication.
  • Do not share your prescription medication.
  • Medications can be dangerous when mixed. Talk to your doctor or pharmacist if you are taking more than one medication, including over-the-counter products and supplements.
  • Plan ahead for refills as needed.

When to contact your doctor

If 4 hours have passed and your penis still has not relaxed, seek emergency medical care.

Warning about medications not prescribed by your doctor

Use caution and talk to your doctor before taking any over-the-counter medications for erectile dysfunction. Some of them may be unsafe.