By the numbers below in this article 20-33% of drugs approved for use in humans are unsafe. Even though this article is about Canada, similar or worse statistics will be found in the US and elsewhere - http://www.sciencedaily.com/releases/2012/10/121008161852.htm
Drugs streamed into Health Canada's accelerated review process are more likely to be withdrawn from the market or earn a serious safety warning than those that undergo the standard review, according to a recent paper out of York University.
"I found that drugs that went through the standard process had a 1 in 5 chance of either having a serious safety warning issued or being withdrawn from the market for being unsafe," says study author Dr. Joel Lexchin, Professor in York's Faculty of Health. "However, if the drug goes through the priority process, it has a greater than 1 in 3 chance of having the same outcome."