dr. bigelow: one can become physically dependent on surprisingly low doses of caffeine. it appears that only about 100 milligrams a day is sufficient to produce physical dependence. that's the equivalent of two or three sodas, or maybe one or two cups of coffee. because the drug is so readily available, it doesn't produce a big problem. so it's an example of a well tolerated, widespread drug of dependence that's just accepted and used in society without major problems. dr. mccaul: among drugs other than alcohol, marijuana is the most prevalent drug of choice in our society. so it does receive widespread use at this point in time particularly among younger people. but that doesn't make it a safe drug any more than alcohol, which is both legal and widespread in its use, is a safe drug. marijuana has toxic effects, because of its route of administration. the inhalation is just as nasty and toxic as cigarette smoking. dr. miotto: there appears to be an increased risk of cancer, of bronchitis, of asthma. the problem is compounded in that many marijuana smokers also smoke ciga

dr. marc siegel is breaking down the good, the bad and the surprisingly unhealthy products found at your local pharmacy. he joins us live from c.o. bigelowmorning, dr. segal. >> we're at america's oldest apothecary. thomas edison came here to have a sore finger treated. eleanor roosevelt has been here, many famous others including peter johnson jr. come here. the question is do people come here for the right things? i'm concerned at this point in time with everything available over the counter, are doctors involved? do patients just choose what they want. we have stomach medications here like zantac. they may be good initially to get rid of a ache but you can get acid rebound. xithromax, centers for disease control say 23,000 deaths occur from overuse of antibiotics. you have weight loss agents. this stuff can rev you up, some people can't tolerate that. are the right people taking the right medicines? >> what about the good stuff? >> ainsley, i think there is good stuff. i think there's a lot of vitamin d deficiency in this country especially with not getting enoughç sunlight. we have vitamin d-3, i recommend this to most of my patient