These are some of the most-prescribed medicines in the U.S., drugs that are so commonplace they are responsible for a huge chunk of the $300 billion spent on brand-name pharmaceuticals each year. That is about to change as patents on these pricey pills begin to expire, opening the door for generic competition. And that can translate to savings of up to 90%, analysts say, making these drugs affordable to more consumers. Americans will see cheaper copies of some of the biggest drug names starting this fall. Out-of-pocket costs of the generic form of Lipitor, a widely used and advertised cholesterol drug that loses its patent protection in November, will be reduced to as little as $4 for a month's supply. Even for a person with health insurance, Lipitor can cost $25 to $40 — or more — each month.