The pharmaceutical industry will need to cast aside its business model of relying on a handful of "blockbuster" drugs for the bulk of its revenue, a recent report from PricewaterhouseCoopers warned. To capitalize on the opportunities that lie ahead, the industry will have to shift its investment priorities from sales to research and development. The situation is hardly dire: the global pharmaceutical market is expected to more than double to more than $1.3 trillion by 2020, according to the accounting giant. Still, pharmaceutical companies are facing a host of challenges including weak pipelines, poor financial performance, rising sales and marketing expenditures, increased legal and regulatory challenges and tarnished reputations. At the same time, healthcare payers and providers have recognized that current healthcare spending is also unsustainable unless they deliver more demonstrable care and cost benefits over the long term. The loss of revenue from blockbusters drugs coming off patent will be the source of a significant amount of pressure on leading companies. The major pharmaceutical companies will lose between 14 percent and 41 percent of their existing revenues as a result of patent expirations in the next few years. Below is a list of selected pharmaceutical companies, the year key products will come off market and their annual revenue from those products.