“Drug” is a word with two very different meanings. On the one hand, it can mean a chemical angel of mercy that may save life or relieve pain. On the other, it can mean a chemical that gives you a good time without the need for human interactions. People tend to approve of the first but, with strictly limited exceptions such as alcohol and nicotine, disapprove of the second.    Some substances, though, fall into both categories. Morphine, for instance, is regarded as fine for those suffering extreme pain but not for those who have merely run out of heroin. At the moment, cannabis is not seen by most authorities around the world as fitting into this dual-use category. And in America, at least, the government seems to be taking fairly effective measures to make sure that nobody does the research that might prove otherwise. But the British government has just proved itself more open-minded. It has issued a license to a small drug company called GW Pharmaceuticals, allowing it to investigate the medical uses of the dreaded weed.   Many doctors believe that cannabis does, indeed, have legitimate medical uses. It reduces nausea and vomiting in cancer patients undergoing chemotherapy. It stimulates the appetites of AIDS sufferers. And it may also help those with glaucoma―an eye disease that can lead to blindness. To test the details of those claims, GW plans to make standardized extracts of the plant, so that dose-controlled trials can be carried out. For that it needs to grow the stuff. And for that it needs the special cultivations and storage license which the Home Office has been pleased to grant.   To prevent patients from developing illness to which they were not previously prone, part of GW 's task is to establish the best delivery method into patients other than smoking. This may not go down well with those in genuine need. What evidence there is from America suggests that smoking cannabis is more medically effective than taking pills containing its active ingredient,THC though whether this is because smoking is a better way to deliver that ingredient, or because the whole plant contains other chemicals that boost the effects of THC, is unclear. If the former is more effective, then the no-smoking signs in hospital wards may have to be modified slightly to make it clear that they only apply to tobacco.