PARSIPPANY, N.J. — U.S. prescription drug spending rose in 2010 but grew at less than half the rate in 2009, according to a new report from the IMS Institute for Healthcare Informatics.

The IMS Health unit said in its “Use of Medicines in the United States: Review of 2010” report that spending for prescription medications edged up 2.3% to $307.4 billion last year, down from 5.1% growth in 2009.

Total spending on prescription drugs via retail channels rose 2% in 2010, and chain drug retailers saw an increased share of that gain.

“Of the 3.99 billion prescriptions filled through retail channels, chain drug stores increasingly were chosen by patients, reflecting both the convenience of these pharmacies and the availability of discounted generics,” the report said. “In addition, chain drug stores continued to acquire independent stores and overall increased their market share by 0.5% last year.”

By dispensed prescriptions, chain drug stores saw the largest gain among retail channels in 2010 with over 2.17 billion prescriptions filled, up 2.1% from 2009, according to the IMS report. Also seeing increases in dispensed prescriptions were mail service (up 1.1% to 264.2 million), long-term care facilities (up 0.9% to 318.8 million) and food stores (up 0.5% to 490.3 million). Prescriptions filled at independent pharmacies dipped 0.8% last year to 748.3 million.

Drug chains were the only retail channel to show share growth of dispensed prescriptions in 2010. Chain drug stores accounted for 54.4% of prescriptions filled last year, up from 53.9% in 2009. Share of dispensed prescriptions slipped to 18.7% from 19.1% for independent pharmacies and to 12.3% from 12.4% for food stores. Share of prescriptions filled held steady for mail service (6.6%) and long-term care facilities (8%) in 2010.

Still, the overall volume of prescription medicines consumed in 2010 rose at historically low levels, IMS pointed out, as the 2.3% rise in prescription sales continued the trend of 5% or lower growth per year since 2007.