A generic drug is a medication that has exactly the same active ingredient as the brand name drug and yields the same therapeutic effect. It is the same in dosing, safety, strength, quality, the way it works, the way it is taken, and the way it should be used. Generic drugs do not need to contain the same inactive ingredients as the brand name product.
However, a generic drug can only be marketed after the brand name drug's patent has expired, which may take up to 20 years after the patent holder’s drug is first filed with the U.S. Food and Drug Administration (FDA).
Generic drugs are usually much less expensive than brand name drugs once they reach the market.
A drug company develops new drugs as brand name drugs under patent protection. This protects their investment in drug research by giving the drug company the sole right to manufacture and sell the brand name drug while the patent is in effect.
When patents or other periods of exclusivity expire, other manufacturers can submit an abbreviated new drug application (ANDA) to the FDA for approval to market a generic version of the brand name drug.