What are the Differences between Pharmaceutical and Herbal drugs? 

Many of the pharmaceutical drugs used today are based on plant constituents and even now, when scientists are seeking for new cures for disease it is to the plant world that they turn. They find, extract and then synthesize in the laboratory a single active constituent from the plant (the active constituent is the part of the plant that has therapeutic value), This can then be manufactured on a large scale. Herbal drugs, however, are extracts from a part of the whole plant (e.g. leaves, roots, berries, etc.) and contain hundreds, perhaps thousands of plant constituents. 

Herbalists believe that the active constituents are balanced within the plant and are made more or less powerful by the numerous other substances present. For example, the herb Ephedra sinica is the source of the alkaloid ephedrine which is used, in orthodox medicine, to treat asthma and nasal congestion but it has the side effect of raising the blood pressure. Within the whole plant there are six other alkaloids one of which prevents a rise in blood pressure.

Synthetic diuretics (drugs that increase the flow of urine) seriously reduce the potassium level in the body which has to be restored by using potassium supplements. Dandelion leaves, however, although a potent diuretic, contain potassium to naturally replace that which is lost.