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What is Erectile Dysfunction?

Erectile dysfunction (ED), also known as impotence, occurs when a man is unable to obtain or maintain an erection firm enough for sexual intercourse.  It is the most common sexual disorder in men, occurring in over half of men aged 40-70.  Younger men are also affected but prevalence increases with age.  This disorder can be psychological, physical or a combination of the two.

In order to get and keep an erection, many factors are involved:

  • Brain and emotions
  • Hormones and chemicals
  • Nerves, muscles and blood vessels

Problems with any of the above may lead to erectile dysfunction

What are the physical causes of Erectile Dysfunction?

  • Heart disease or clogged blood vessels (these are the most common causes)
  • High blood pressure or cholesterol levels
  • Diabetes
  • Thyroid disease
  • Being overweight
  • Low testosterone
  • Certain over the counter or prescription drugs
  • Tobacco, alcohol or illegal drug use
  • Prostate problems
  • Surgery, injury or diseases (e.g. Multiple Sclerosis and Parkinson’s) affecting the nerves involved in the mechanics of an erection

What are the emotional causes of Erectile Dysfunction?

  • Mental illness such as depression or anxiety
  • Stress
  • Problems with partner
    • Communication issues
    • Conception issues
    • Stress and anxiety as a result of erectile dysfunction or other factors

What are the Symptoms of Erectile Dysfunction?

The three common symptoms of ED are problems with:

  • Getting an erection
  • Keeping an erection
  • The desire to have sex

Most men will experience these symptoms occasionally in their lifetime but those who experience such symptoms on a frequent basis should seek treatment.  Seeking help is important because the underlying cause of ED could be related to heart disease. Also men with ED often develop an unhealthy sexual pattern that over time could lead to premature ejaculation (PE).

What is the treatment for Erectile Dysfunction?

The first step is to identify and treat any of the physical or emotional causes of ED as some can lead to more serious conditions if they go ignored or untreated.

Available treatments consist of:

  • Phosphodiesterase type 5 (PDE-5) inhibitors such as Viagra (sildenafil), Cialis (tadalafil), Levitra (vardenafil) and Spedra (avanafil) are very effective in treating erectile dysfunction.  Success with each varies from patient to patient.  A table has been included below to summarise some differences between these drugs.
  • Alprostadil which can be injected into the penis or inserted into the urethra is ideal for certain patients, especially those who can not take the previously mentioned oral drugs
  • Vacuum erection devices (penis pumps)
  • Penile implants or other surgery (when nothing else has helped)
  • Counseling works well alone and in combination with other therapies to address the psychological causes of ED

How do the PDE-5 inhibitors compare?

Spedra, Viagra, Levitra and Cialis are all PDE-5 inhibitors.  Although they are different drugs with different chemical structures and doses, they work in the same way to produce an erection.  A major difference between these drugs is the time they take to work (onset) and how long they last in the body (duration of action). 

There is no “best” drug for ED because one might work better in one person than in another.  Sometimes a trial of multiple drugs (using one at a time) is needed to see which one works best for you.  It makes sense to consider if onset or duration of action matters to you.  In addition, if you do experience side effects, a shorter acting or lower dose could be the answer.


Onset (Minutes)

Duration of action (Hours)


Spedra (avanafil)

15-30 minutes
Take 30 minutes in advance

4-6 hours

Fast onset
Shorter duration of side effects


30-60 minutes
Take 45-60 minutes in advance

4 hours

Effective with mild side effects.  First, most widely recognized and popular as a result.

(Viagra’s generic)

30-60 minutes
Take 45-60 minutes in advance

4 hours

Less expensive than Viagra

Levitra (vardenafil)

Within 30 minutes
Take 30 minutes in advance

4-6 hours

Fast onset
Shorter duration of side effects

Cialis (tadalafil)
36 hour

30-45 minutes
Take 45 minutes in advance

24-36 hours

Long acting

Cialis (tadalafil)

Once daily dosing is initiated there is no wait time because a constant low dose is always present

Any time sexual arousal occurs

Long acting
As long as it is taken daily, there is no need to remember to take right before sexual activity