What is the difference between a drug and an herb? The best answer is: An herb is a plant or plant part used in its entirety, while a drug is a synthesized copy of one chemical component, such as a component found in an herb.

Herbalists prefer using the whole herb and believe that one of the reasons why herbs have fewer side-effects is because of a balance of naturally occurring ingredients. Pharmaceutical companies like to isolate chemicals so they can produce a "pure" concentrate, acquire a patent, and reap large profits. Whole herbs can't be patented so there is little profit potential for the drug companies.

Every herb consists of hundreds or even thousands of naturally occurring chemicals. The actions of most of these chemicals are not understood, but it is known that an herb's total effect is a result of the combination. Some chemicals have synergistic effects on others increasing their activity. Some modify the effects of others reducing undesirable side-effects.

Scientists and herbalists will often use the term active, as a noun, to refer to what they consider to be an "active" ingredient of an herb. For example, hypericin and hyperforin are considered to be the actives in the herb St. John's wort. This is useful when it comes to standardizing an herb or when testing it for quality, but it is a little misleading if we believe that the actives are the only beneficial ingredients in the herb. The benefits that St. John's wort provides are not just a result of these two chemicals, but of a synergisticinteraction between these two chemicals and a host of other naturally occurring chemicals found in the herb.

Pharmaceutical companies often make the mistake of isolating an active from an herb, or extracting that active out of the herb without the herb's other naturally-occurring ingredients; or even worse, of making and producing a synthetic copy of the active. What they end up with is a drug that is far from what nature produced—without the benefits of the synergistic interactions of the herb's original ingredients—often resulting in negative actions or undesirable side-effects.


Herbalism as "Alternative Medicine"

Sometimes people speak of herbalism as alternative medicine. The implication is that the conventional corporate pharma-toxicological medicine as practiced in the Western world is the standard, and that anything else is an alternative. But most herbalists see it the other way around. Herbs have been around for millennia. The World Health Organization estimates that healing herbs are currently the primary medicines for two-thirds of the world's population—or some four billion people. Most of the tools currently used by modern medicine, including most of the drugs that are in use today, have only been around for a few decades or less. If anything is an alternative, historically speaking, it is the pharma-toxicological medicine that is currently practiced in Western nations.

(source : http://www.theherbspecialist.com/difference-between-herbs-and-drugs.html)