"Pfizer has two patents for Viagra, one for its chemical, expiring in 2012, and the other for its use against impotence, expiring in 2019.

The chemical patent expires on March 27, 2012. Pfizer may be able to extend it another six months, to September 2012, under a federal law called the Best Pharmaceuticals for Children Act. The law is meant to encourage drug companies to study children’s uses, often a difficult and unprofitable area.

In this case, what would be studied is not Viagra for children, but Revatio, a formulation of the same chemical, sildenafil, which is approved for pulmonary arterial hypertension, a rare and dangerous condition affecting hundreds of children in the United States. Mr. Jimeson said the company was working closely with the Food and Drug Administration to discuss the pediatric studies of Revatio and the potential for an extension on the chemical patent, which would also protect Viagra and its prices.

Many men, though, have waited years for a lower-priced Viagra and their wish may come true next year."

Unless Pfizer is successful in finding a use for Revatio in children, generic versions can be marketed (after approval) after  March 27, 2012. The only difference in Viagra and Revatio is the dosage, Revatio is 20 mg tablet taken three times a day (60mg). Viagra recommended is 50mg. It also comes in 100mg & 25mg. It can be taken in 25mg for some; some even need more that 100mg.

From Pfizer's website "VIAGRA should not be used with REVATIO as REVATIO contains sildenafil, the same medicine found in VIAGRA."

Pfizer is busy modifying Viagra (Viagra Jet sold in Mexico) and establishing more brand strength. That is because they will soon lose the chemical patent. They can protect Viagra until 2019 in the US (even though they have lost that patent in other countries.)

When the chemical patent for sildenafil expires, other manufactures can produce generics when dosed and labeled for appropriate usage other than erectile disfunction. Many drugs are prescribed and used off label. While you insurance company would not approve and cover generic Revatio for you unless you have PAH, the low cost will make it unnessesary to use insurance. It is very easy to find a doctor who will prescribe 'off label' but for good reason. In general, doctors loath insurance companies and the games that Big Pharma play.

By summer, you just might be able to go to Walmart and get your $4 bottle of generic Via... sildenafil.