Scientists May Use Drugs to Stop Addiction By MALCOLM RITTER    NEW YORK (AP) -- Can Prozac help you kick cocaine? Can Ritalin? How about a blood pressure pill or medicine for muscle spasms? If you're an alcoholic, could you get help staying sober by taking an anti-nausea drug used by cancer patients?    Scientists are exploring those questions right now. In fact, in the field of addiction medicine, one of the hottest sources of new drugs is .....