IMS Health’s annual US Pharmaceutical Market Performance Review showed that the sales of Rx drugs in the United States only grew 3.8% in 2007, compared with 8% seen in 2006. It is the lowest growth rate since 1961.

The total US Rx drug sales hit $286.5 billion last year, with the declining growth rate partly attributed to expirations of patents on lucrative medicines, which paved the way for cheaper generic versions. IMS Health also cited fewer new product approvals, safety concerns, and the leveling of year-to-year growth from the Medicare Part D program.

The brand name drugs with approximately $17 billion in sales lost patent protection in 2007, opening the door to a 10% growth for generic medicines. IMS Health found that generic drugs were responsible for 67% of US prescription drugs dispensed in 2007. The company predicts compound annual US pharmaceutical sales growth of 3% to 6% through 2012. The group noted that new biotech drugs and vaccines as well as the estimated launch of a small group of drugs with a potential of at least $1 billion a year will help offset major patent expirations.