If Pfizer conducted clinical trials and got Viagra approved for a new indication, they could extend their exclusivity two different ways: either through a use patent or through market exclusivity as provide by the FDA.
However, if their patent is around the use of the drug, i.e. erectile dysfunction and that patent runs out, another company could make a generic. That company would not be able to promote the drug for the new indication, but doctors would know the two were the same and could prescribe the generic.
If Pfizer conducted clinical trials and got Viagra approved for a new indication, they could extend their exclusivity two different ways: either through a use patent or through market exclusivity as provide by the FDA.
However, if their patent is around the use of the drug, i.e. erectile dysfunction and that patent runs out, another company could make a generic. That company would not be able to promote the drug for the new indication, but doctors would know the two were the same and could prescribe the generic.