April 20, 2011 -- The 10 most prescribed drugs in the U.S. aren't the drugs on which we spend the most, according to a report from the IMS Institute for Healthcare Informatics.

The institute is the public face of IMS, a pharmaceutical market intelligence firm. Its latest report provides a wealth of data on U.S. prescription drug use.

Continuing a major trend, IMS finds that 78% of the nearly 4 billion U.S. prescriptions written in 2010 were for generic drugs (both unbranded and those still sold under a brand name). In order of number of prescriptions written in 2010, the 10 most-prescribed drugs in the U.S. are: