Last spring Canada became the first and only country to approve a drug called Sativex to treat the chronic pain endured by most of the 2.5 million people with multiple sclerosis. The announcement caused, ahem, quite a buzz. Sativex is a whole-plant extract of high-grade Cannabis sativa, a.k.a. marijuana, and is the first prescription drug to contain all 60-plus of the plant's cannabinoids, those compounds that include the psychoactive chemical THC. Although the drug packs a pain-numbing punch, its mouth-spray formulation slows its release into the body, thus diminishing those consciousness-altering side effects associated with smoking marijuana.