When a pharmaceutical company first develops a new drug it takes out a patent (exclusive rights) to ensure that no other company can manufacture or sell the drug. The patent normally lasts around 20 years but can be extended under special circumstances.

It can take about 10 to 15 years of this period to develop the medicine and obtain regulatory approval. Then they will produce and sell it, or give permission for others to do so. Also, the brand name of an original medicine is usually protected as a trade mark and cannot be used by anyone else.