Most herbs have not been studied as extensively as have drugs. As a result, it is often not known exactly which chemicals in herbs are the active ingredients. Similarly, the side effects of herbs and their interactions with drugs are not fully understood. In summary, even for well-studied herbs, the full range of effectiveness and the full range of side effects are not completely known.
Another important aspect of herbs is their variability. Because of the current lack of strict regulation in the United States, a great deal of variability is present in the quantity of the presumed active ingredient present in different herbal preparations. For example, one study of ginseng found 50 times as much of the active ingredient in some products as in others; this situation is similar to a physician telling a patient to take somewhere between one and 50 pills for a medical condition! Other reports have found no active ingredient in some ginseng preparations.
Finally, herbs should be avoided in certain circumstances. People should avoid herbs if they have multiple medical problems or are taking multiple medications; women who are pregnant or breast-feeding and children also should avoid herbs. Some medications have a very specific range in which they are effective and in which they do not have side effects. These include anticonvulsant medications, blood-thinning medications, and some heart medications. Herbs should not be taken with these medications because we do not know all of possible interactions that herbs could have with them. Some herbs could mildly alter the blood levels of these medications and thereby decrease their effectiveness or increase their side effects.
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