You mean patent not patient right? The drug cos extend patent status by getting FDA approval for new indications. e.g. risperdal getting labeled for irritability in autistic kids in 2007. If that fails, they just roll out the new drug that they’ve had waiting in the pipeline. There really isn’t a huge investment or cutting edge technology involved to develop the new drug. It is just a minor variation of the old drug. As long as it can be argued that it is unique, it will get a new patent.