Here is a link to an article from the pharmaceutical business review online about a generic version of a treatment for high blood pressure. The patent on medecine in question has expired so it is not protected generic versions are legally allowed to be distributed. Interestingly, it seems that the producer of the generic version has exclusivity on the product for 180 days. This protection seems to be given directly by the FDA.

http://www.pharmaceutical-business-review.com/article_news.asp?guid=9058A990-8D4D-4202-947F-F4FDD767AA23