June 28 (HealthDay News) -- U.S. hospitals that switched from using doctors' handwritten prescriptions to computerized drug ordering systems had a 66 percent drop in medication errors, say the authors of a review that looked at the results of 12 studies.

The findings are published online in the journal Health Services Research.

Almost 25 percent of U.S. hospital patients experience medication errors, such as receiving an incorrect dosage, the wrong drug, medication at the wrong time, or no medication at all. Each year, medication errors injure or kill more than 500,000 U.S. hospital patients, according to background information in the review.

Illegible handwriting on prescriptions and transcription mistakes cause as many as 61 percent of medication errors, the experts said.

"These medication errors are very painful for doctors, as well as the patients. Nobody wants to make a mistake," lead author Tatyana Shamliyan, a research associate at the University of Minnesota School of Public Health, said in a prepared statement.

She and her colleagues found that hospitals with the highest rate of medication errors -- more than 12 percent -- showed the most improvement when they switched to computerized drug ordering systems.

They also found that while the use of computerized systems reduced medication errors overall, there was no decrease in one type of error -- prescribing the wrong drug.

Currently, only about 9 percent of U.S. hospitals have computerized prescription systems, which can take 12 to 36 months to implement.

SOURCE: Center for the Advancement of Health, news release, June 27, 2007