Sales growth of prescription drugs in the U.S. slowed for the second straight year, with the economic downturn playing a key role, according to IMS Health Inc.

Market research firm IMS cites lower demand for less-expensive generic drugs, lagging new product sales, and reduced consumer demand. Sales rose just 1.3 percent to $291 billion in 2008. That about matches IMS' prior outlook of 1 percent to 2 percent growth.

In 2007, U.S. sales rose 3.8 percent to $286.5 billion, while they gained 8 percent in 2006.

Anti-psychotic drugs were the lead sales drivers, followed by cholesterol drugs and treatments for heartburn and related conditions.