According to the May 26, 2005 issue of the New England Journal of Medicine, "most major drugs are effective in only 25 to 60 percent of patients, and more than 2 million cases of adverse drug reactions occur annually in the United States, including 100,000 deaths."
So what does this mean for you?
Now, I know this is an older study, but not much has changed since then. The above is a reason to stick with natural herbs that work with you body's natural chemistry rather than against it using synthetic compounds. Though herbs & certain supplements are considered "natural" they can still have powerful effects or adverse effects if used improperly. Therefore, its in an individuals best interest to only use herbs under the guidance of a qualified, licensed herbalist. As for what one can purchase over the counter, research it. There's a wealth of quality information online or just ask a qualified professional.