Erectile dysfunction is defined as the consistent inability to maintain an erect penis. Many factors can contribute to the onset of ED. The problem can be physical or psychological in nature. Psychological causes could be fatigue, stress, performance anxiety etc... Physical abnormalities are classified as follows:

  • Urological: congenital or infection-induced condition of some uncircumcised males in which the foreskin prevents the maintenance of erections.
  • Vascular: This is an impairement of the blood circulation to the penis which can be seen in men with hypertension and/or diabetes mellitus. Problems can be from arterial inflow or venous outflow.
  • Neural: Degraded neural pathways to the lower body will impair erection.
  • Endocrine: Excessive release of hormones can lead to erectile dysfunction, mainly through the decrease of sexual interest.
  • Iatrogenic: This condition is caused by medical or surgical therapy for other disorders. The most frequent one is the removal of the prostate gland. It is also estimated that about 25% of all cases of ED are due to the side effects of other drugs.
  • Dietary: ED has been linked to the deficiency in zinc.

Before Viagra, there were already quite a few products out on the market to help those suffering from ED. These are summerised below.

Other products available:
Therapeutic Option
Vacuum constriction devise (for venous disorders) Reliable, safe, cost-effective Interruption of sexual act
Penile prosthetic implants (rigid, malleable, hinged or inflated) Cosmetically satisfactory Multiple surgical procedures usually necessary
Surgery (arterial balloon dilation, arterial bypass, or venous ligation) It is a semi-permanent solution if ED is mostly due to vascular problems Risks of surgical procedure

In addition to these solutions, various injectable drugs are available. These are injected into the base of the penis about 5-15 minutes before an erection is desired. Two examples of these are shown below, alprostatil is thought to cause vasodilation of the penis by causing the increase of cAMP which contributes to penile arterial dilation. Papaverine inhibits PDE enzymes.

With these examples, the advantages of Viagra are made clear. It is taken orally, which means it is much easier to use than the drugs which have to be injected. It does not interfere with the sexual act which also explains its appeal to people. It does not involve any surgery and therefore eliminates all the dangers due to that. Viagra does not have any of the problems which are associated with the therapeutic options shown in the table above. However, it can be noticed that Viagra acts in the same way as papaverine, it inhibits PDE enzymes.