Patents are about to expire on two of the world's best-selling prescription drugs. Prices for cholesterol-fighter Lipitor and the blood-thinner Plavix are likely to drop by 80 percent when they're replaced by generics. But that's not all. The drug industry will be faced with an unprecedented wave of expiring patents in the next few years. What will the expiration of patents on many other drugs mean for Big Pharma? How is the industry fighting back? Will consumers get the benefits they deserve?