We have legal addictive substances-- tobacco, alcohol, caffiene, maybe others-- that aren't regulated as drugs. We have legal nonaddictive (or not-recognized-as-addictive) substances-- aspirin, Prilosec, dextromethorphan-- that are regulated as drugs and sold over the counter. We have legal substances, some of which are addictive, which are sold by prescription only via a pharmacist. (Some of which are also sold illegally via a black market, if there's a demand that isn't being met by prescription use). When you say that "it is a drug and should be treated and regulated as one", which of these do you mean (or do you mean something else), and what problems would your preferred option solve?

If you require people to get prescriptions for cigarettes, and you might as well make them illegal-- no doctor is going to write such a prescription on pain of malpractice suit. Sell them over the counter, and it's not all that different from current regulations-- a little more freedom for advertising, maybe a little less for venue. (Most OTC drugs don't have an age limit, but odds are that'd be kept for tobacco.) Treat them like alcohol, and again it's not all that different from the present, modulo some restrictions on times and places sold. Or there may be an option that I'm missing.

(I have no major problems with legalizing other drugs, but I'd expect them to be treated... well, about the way cigarettes or alcohol are today: age limits, limits on which stores can sell them, wide zones where public use or abuse is criminalized or otherwise discouraged, high taxes, etc.)