Morphine substitute is just as strong, without side effects (in rats)

Morphine is a highly effective painkiller, but it comes at a price -- it's also extremely addictive. It's incredibly easy to build up a tolerance to the drug too, meaning patients need higher and higher doses to achieve the same pain-killing effect they had previously experienced. 
But now researchers at the Tulane University School of Medicine have developed a new drug that they say is as effective a painkiller as morphine but without any of the side effects. By: Emily