For some types of inventions, such as new and nonobvious pharmaceutical compositions, securing a patent from the federal government is only half the battle. In addition to obtaining patent rights, pharmaceuticals and other compositions that might be consumed by humans are required to undergo a review process conducted by the Federal Food and Drug Administration.
Patent rights prevent others from making, using, selling or importing the patented invention. But patent rights are only enforceable for a set amount of time (twenty years from their filing date), and the prosecution of the patent application can take a number of years on its own. But even if a patent is issued for a novel pharmaceutical composition, that does not mean that the pharmaceutical company can immediately go sell the product. New pharmaceuticals cannot go to market without FDA approval.