generic drug

A generic drug is a copy of a brand-name medicine that other manufacturers are allowed to make once the original's patent has expired. The active ingredient is the same molecule, in the same strength and dosage form, doing the same job in the body. The familiar difference is the price: without the long original development costs to recoup, generics are usually far cheaper.

When a company invents a new drug it gets a patent giving it years of exclusive selling rights, which lets it charge a high price to recoup the enormous cost of development. When the patent runs out, that monopoly ends and rivals may sell the same active substance under its plain chemical or nonproprietary name rather than the original brand. Competition then typically drives the price down sharply.

A generic must contain the same active ingredient at the same dose as the original, but it does not repeat the full clinical trial program. Instead the maker must show bioequivalence: that the generic delivers the active drug into the bloodstream at essentially the same rate and extent as the reference product, so it can be expected to work the same way. Inactive ingredients such as fillers, dyes, or coatings may differ.

For most medicines a quality-assured generic is interchangeable with the brand. A few exceptions deserve care, particularly drugs with a narrow therapeutic window where small swings in blood level matter, since even bioequivalent products are allowed to vary slightly. Differences in inactive ingredients can also matter to a patient with a specific allergy.