THE VIRILITY: NO CONNECTION
Now it was acknowledged that an erection was a multistep chemical process which began with an increase of blood flow through the penile arteries. Nitric oxide, the critical messenger in the muscles, must be present. And, according to the Pfizer researchers, so too must cyclic GMP (guanosine monophosphate), which is the “message” within the muscles that directs them to relax and allow blood to flow.
Sildenafil amplifies this entire process. When it is taken before a romantic encounter, and then followed by sexual stimulation, the entire chemical sequence kicks in without interference. According to Dr. Ian Osterloh, the Pfizer researcher who directed the ensuing sildenafil clinical trials throughout Europe, the drug is an extremely effective inhibitor. What sildenafil does—and does so well—is block a subtype of phosphodiesterase called phosphodiesterase type 5, which is a specific enzyme that hinders the effects of NO. As nature arranged it, this enzyme happens to be in large supply in the penis. Sildenafil prevents the breakdown of cyclic GMP by phosphodiesterase type 5, thereby allowing NO to do its job of relaxing the penile arteries and allowing blood to flow into the corpora cavernosa. And by preventing blood from flowing out of the penis, sildenafil helps provide a firm erection.
The amazing quality of the drug was described by Dr. Osterloh. In the past,” he says, “the major reason we had trouble finding a drug that would cause an erection is that the penis contains blood vessels, sinusoids (the three spongy chambers essential to erection: the two corpora cavernosa and the corpus spongiosum), blood spaces, and smooth muscle cells. But so do a lot of other organs in the body. So, if a man took a drug that caused an erection by dilating blood vessels in the penis, it always caused dilation in other parts of the body as well— many times with some very undesirable side effects.”
Finally, with the discovery of sildenafil, there appeared to be a solution for ED that worked specifically where it was needed, and nowhere else in the body.
The next step was to set up clinical trials in order to see just how effective a drug sildenafil was. This was a crucial process because the history of medicine is full of stories about promising medications that worked beautifully on a handful of test subjects. However, when tested scientifically on hundreds of people in double-blind, randomized, two-way, crossover studies, many have failed miserably. Some weren’t all that effective. Others produced severe side effects—and sometimes they caused death. At that awful point, the trials would be halted. But with sildenafil there would be dramatically positive results.
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