Between 2005 and 2010, 113 primary care doctors wrote more than 250,000 prescriptions for just over 50,000 patients. Eleven percent of those prescriptions were considered "off-label" by the standards of the Health Canada drug database. The researchers didn't have information on how well those drugs ended up working for the patients who took them. But they determined that four out of five off-label prescriptions didn't have strong evidence suggesting they were likely to be effective.