Introduction
Definitions of ED
"Erectile Dysfunction is the consistent or recurrent inability of a man to attain and/or maintain a penile erection sufficient for sexual performance." (1st International Consultation on ED sponsored by the World Health Organization, July 1999)
"Erectile Dysfunction is the persistent or repeated inability, for at least 3 months duration, to attain and/or maintain an erection sufficient for satisfactory sexual performance." (Process of Care Consensus Guidelines Panel; December 1997)
"Erectile Dysfunction is the inability of the male to attain and maintain erection of the penis sufficient to permit satisfactory sexual intercourse." (National Institutes of Health Consensus Development Conference on Impotence; December 1992).
Some statistics about ED
Scientists have discovered that erectile dysfunction is much more prevalent than they ever expected. It is age-related, chronic, prograssive and it is also greatly under-treated. The scenarios described in this overview provide a concise look at some reasons why many men and their spouses falter at the thought of seeking help. Compared to many other societies, America is still embarrassed and bashful about sex. However, that view is changing. Sex is becoming more openly discussed on television, in the movies, on the Internet and in private. This new-found openness is encouraging more and more individuals to seek medical treatment.
The medical consensus is that erectile dysfunction is prevalent in about 10 million to 20 million men. Up to 30 million men suffer at least partial erectile dysfunction. The medical community also agrees that about 80% of all erectile dysfunction has a physiological component or cause, and is not psychological.
The Massachusetts Male Aging Study showed very clearly that ED was highly prevalent with 52% of the sample of men 40-70 years old reporting ED Figure 1 . Age was the strongest correlate of both the total prevalence of ED and the prevalence of complete ED. At age 40, the total prevalence of ED was 39% and the prevalence of complete ED was 5%. At age 70, the total prevalence of ED was 67% and the prevalence of complete ED was 15%. In all age groups minimal ED remained the same, but the moderate and complete categories increased with age.
Statistically speaking, the vast majority of men for one reason or another refuse to seek a medical professional. The medical community approximates that less then 25 % of men with this ailment seek medical help. While the introduction of Viagra has increased the percentage of men seeking treatment from about 5% to around 25%, this percentage is still small compared with the number of men who actually
The Mystery of an Erection
Simply stated, an erection is a result of an increased flow of blood into the penis and a decreased outflow. Clearly, this is the simplest of definitions. However, in order to study how oral medications work, we must look at a more appropriate and complex definition.
When a man is sexually stimulated, either physically or mentally, two nerve pathways are activated Figure 2. The first pathway causes a reflex erection through the sacral spinal cord (lower end of spinal cord). No connection to the brain needs to occur, which explains why a man with a spinal cord injury is often still capable of producing an erection. The second nerve pathway occurs between the brain and the multitude of nerves within the penis. When stimulated, these nerve cells create nitric oxide, which causes the penis to form a chemical called cyclic guanosine monophosphate, commonly referred to as cyclic GMP or simply cGMP.
Cyclic GMP dilates (opens and broadens) the blood vessels within the penis allowing it to engorge with blood. The result is a rigid and erect penis. In normal circumstances, a man continues to produce abundant amounts of cGMP for the duration of the sexual stimulation in order to maintain sufficient rigidity for penetration. Simultaneously, another chemical known as Phosphodiesterase-5, or PDE-5, diminishes the effects of cGMP and creates an equilibrium between the two chemicals. This balancing act allows the erection to continue Figure 3.
Once a man's sexual arousal dies down, or stimulation ceases, cGMP production comes to a halt. With PDE 5 as the predominant chemical, the penis returns to its flaccid state.
Knowing the chemistry of what causes an erection helps with understanding how PDE-5 inhibitors, such as Viagra, Cialis and Vardenafil work in the body. These medications block or hinder PDE-5 production, so that the opposing chemical cGMP continues its role in keeping the penis rigid. Remember that cGMP is the chemical produced during arousal in response to stimulation. With PDE-5 hindered, the faucet is left open, so to speak. The blood vessels remain broadened and engorged within the penis, and the erection is more easily maintained. The chances of an erection ending prematurely are significantly reduced.
Another discovery researchers made while studying PDE-5 inhibitors is that it works so well because it is a very specific medicine. In other words, Viagra, Cialis and Vardenafil have an effect on the physiology of the penis but has little or limited side effects on the rest of the body |
