Sildenafil citrate (VIAGRA)

After reading an article about ED that had a questionnaire to see if I fit the profile, I was surprised to find that I did. I had thought that ED was for guys that couldn’t get erect at all, but while I could, I didn’t always successfully maintain it. And once lost I couldn’t get hard again for many hours. Pretty disconcerting when after 30 minutes of hot foreplay, the wife is revved up and I only have a limp noodle to work with. So I ordered Viagra and didn’t tell the wife.

Just like others have written I experienced a mild headache and nasal congestion. But and once prompted, it didn’t take much, I got a rock hard erection that lasts longer than I’ve ever had. I stayed hard longer than ever and gave her quite a workout. And if I can keep her interested, I can get hard again in about 15-20 minutes after I cum. I still haven’t told her which makes spontaneous sex a little tricky. I’ve been ready to go more than once and we’ve been interrupted, which can be uncomfortable. Now I don’t worry about be able to perform and look forward to those many romantic weekend getaways where we never leave our room. - Kevin, Age 49

In 1991, healthy volunteers took part in clinical trials to test the safety of Viagra and how the body metabolised the compound.

These showed that it was safe. In trials over 10 days, the healthy volunteers reported some unexpected side effects. Male volunteers reported more frequent erections after taking the Angina medicine!

Erectile dysfunction

Following the unusual side effects seen in the volunteer trials, researchers switched to looking into using Viagra to treat Erectile dysfunction (ED). This serious condition causes psychological and emotional problems that affects many families.

Research into using Viagra to treat angina continued but the medicine did not prove powerful enough to be really useful.

Sexual stimulation leads to the local release of nitric oxide (NO) from nerve endings and endothelial cells in the spongy erectile tissue — the corpus cavernosum — of the penis. NO switches on the enzyme guanylate cyclase, which converts guanosine triphosphate into cyclic guanosine monophosphate (cGMP). This key second messenger is a vasodilator — it relaxes the vascular smooth muscle of the blood vessels of the corpus cavernosum, so that the blood flows more strongly leading to an erection. However, at the same time cGMP is hydrolysed by phosphodiesterase type 5 enzyme (PDE5), to inactive GMP.

Men who have erectile dysfunction (ED) are often producing insufficient amounts of NO. So although they are producing a small amount of cGMP, it is being broken down at the same rate. Viagra works by blocking part of the cycle. It selectively inhibits the PDE5, by binding with PDE5’s active site. This prevents the hydrolysis of cGMP to inactive GMP, allowing cGMP to accumulate and prolong the vasodilation effect.

Because of this mechanism of action, Viagra works regardless of the underlying cause of ED. It is effective in men with ED associated with a variety of medical conditions, including vascular and neural disease, diabetes, prostate surgery, depression and spinal injury (providing sufficient nerve has been left intact). Whatever the cause of reduced NO formation, Viagra still works. However, Viagra is not an aphrodisiac. Because the drug is potentiating the natural effects of cGMP rather than stimulating its production, it only works in response to sexual stimulation.