Hospitals that replace doctors' hastily written prescriptions with electronic records reduce medication errors 66 percent, researchers say.

Tatyana Shamliyan, who led a study for the University of Minnesota, said that transcription errors cause as much as 61 percent of medication errors. Decimal points can be misplaced, and common medications -- such as pain medication Celebrex and antidepressant Celexa -- can be confused.

The problem is widespread, with studies showing that nearly 25 percent of hospital patients experience an error. The rate was thought to be 5 percent in 1992.

That means that more than 500,000 people a year have an adverse effect from a prescription error, which is generally the only way problems are noticed.

Currently, only about 9 percent of hospitals have computerized prescription systems. Some hospitals have stand-alone systems, while others have computerized prescriptions as part of an electronic medical record system.