Viagra became a smashing success almost immediately upon its release. The success of Viagra was quickly evident in the level of popular interest it generated, and then in the big profits it brought in. The initial profit margin for Viagra was millions of dollars. Move forward a few years, and Viagra is now a billion dollar profit seller.

Viagra's success is rather a surprise, because Viagra is only available to one part of the population -- men -- and is a treatment for what was thought to be a fairly limited condition: erectile dysfunction. Compare this profile to a drug for depression, for example: a depression drug is available to an entire population and treats a condition that's fairly common. How does Viagra's limited profile generate so much profit?

Viagra's profit success may be attributed to one of two things. Explanation number one is that a considerable amount of men have erectile dysfunction. Men who were older and sickly, what would have to be a small percentage of the male population, were thought to be typical candidates for erectile dysfunction. Viagra's big sales numbers, however, indicate that older and sickly aren't the only ones who may have erectile dysfunction. Perhaps erectile dysfunction is epidemic?

The second possibility for explaining Viagra's huge sales is men without erectile dysfunction are using Viagra. Why? Viagra has developed a reputation for being a male aphrodisiac, and a section of men could be using Viagra for male enhancement. Though Viagra is a prescription drug -- in the US at least -- could a man with a claim of erectile dysfunction have that claim somehow disproved? Possibly. Possibly not.

The open secret about Viagra, and some other drugs, is that it's available without having to go to one's personal physician for a prescription. Online sources, often referring to themselves as pharmacies, will either arrange for an online prescription to be obtained, or will sell Viagra without a prescription outright. Authorities are clamping down on these so-called online pharmacies, however, so they may not be the viable option they once were.

Viagra's overwhelming success has, not surprisingly, encouraged competition. There are now two other prescription drug alternatives to Viagra: Cialis and Levitra. Both of these drugs -- and Viagra -- have massive marketing campaigns that include prime time television commercials. (The fact that treatments for erectile dysfunction are now advertised on prime time television in the United States is a story in itself.)

Viagra's success has also produced competition from nonprescription products, products different from Viagra in they are designed specifically for intimacy enhancement and not erectile dysfunction. These latest competitors to Viagra are becoming increasingly popular and a new niche -- nonprescription enhancers -- is developing as a result.