demand has been growing for handheld tobacco vaporizers like those made by Ploom (which charges $250 for its "premium loose-leaf vaporizer"). "There's a rush now to make the ideal vaporizer," Dayton says. "There's still room for a kingmaker in this space." In the meantime, at least one drug company is directly selling medical marijuana to patients around the world. GW Pharmaceuticals /quotes/zigman/286334 /quotes/nls/gwprf GWPRF +0.19% , based in London, markets Sativex, billed as the world's first marijuana-based medicine. With a market cap of around $137 million, it's listed on the Alternative Investment Market, a submarket of the London Stock Exchange. Sativex is currently sold as a mouth spray to help alleviate symptoms of multiple sclerosis in several countries, including the U.K., New Zealand, Germany, Spain, Denmark and Canada, a spokesman says, and it is currently seeking FDA approval in the U.S. for use as a pain reliever in late-stage cancer patients.