Doshas, namely, Vayu, Pitta and Kapha are spread all over the body. They regulate functions of every tissue cell and are present in each of them. When the sperm and the ovum unit in the uterus of the mother to form a zygote, the doshas present in them and outside them in the uterus cause certain characteristic features which in Ayurvedic parlance are known as prakriti. If all the doshas are in the state of equilibrium, it gives rise to a healthy foetus, and the child born of it leads a very healthy life. If the doshas are very much in a disturbed state, then it either prevents conception, or does not allow the zygote to grow, or results in malformations. If, however, one or two of these doshas are in excess, they give rise to a type of physical constitution and psychic temperament of the individual born out of it. Theses characteristic features of the body and the mind remain with the individual throughout his life. It does not change, and any change in it is indicative if death. Seven types of prakriti are recognised in Ayurveda with their specific characteristics.

For Ayurvedic treatment, knowledge of prakriti is very important. For example, a person of vata prakriti is always likely to get vatika type of diseases and in him diseases of other type do not give much trouble, or are easily curable. To prevent the occurrence of diseases, the individual having vata prakriti should always avoid such factors as would aggravate vata and resort to vata-alleviating food, drinks and regime. Food ingredients which are unctuous and hot are likely to suit him most whereas to a pitta prakritiman cold things will be more suitable. Similarly, while administering medicines, other things being equal, a pitta prakriti patient is to be given cooling medicine and a kapha prakriti patient is to be given heating medicine having bitterness, dryness, roughness, etc. Quinine, for example, can be safely given to a kapha prakriti person. It will not be very suitable for an individual having vata prakriti.

Drug Composition: Like other things in the universe, a drug is composed of the five mahabhutas, namely, akasha, vayu, tejas, jala and prithvi. From the physical appearance alone, it will be difficult to ascertain bhautika composition of a drug. It has to be ascertained on the basis of the taste of these drugs. For example, if a drug is having sweet taste, then it is to be inferred that it is predominated by prithvi and jala and agni mahabhutas. One having saline taste is dominated by prithvi and agni mahabhutas, on having pungent taste is dominated by agni and vayu mahabhutas, one having bitter taste is dominated by vayu and akasha mahabhutas, and one having astringent taste ins dominated by prithvi and vayu mahabhutas.

As has been described before, the doshas in the body are also composed of these five mahabhutas, i.e., kapha is dominated by prithvi and jala mahabhutas, pitta is dominated by agni mahabhuta and vayu is dominated by vayu and akasha mahabhutas.

If a disease is cause by the aggravation of kapha dosha, then the individual should be given drinks and drugs which have less of prithvi and jala mahabhutas, but more of agni, vayu and akasha mahabhutas. From out of these three mahabhuta. Therefore, medicines having these tastes, namely, pungent, bitter and astringent, are administered to a patient having a disease dominated by kapha dosha. The same rule will govern the selection of drugs for disease caused by other doshas also.

The above is only a brief explanation of the action of Ayurvedic drugs. There are many other factors which are taken into consideration which are taken into consideration while selecting a drug. They are attributes (gunas), the potency (virya), the taste that comes out after the material is digested (vipaka) and the specific action (prabhava). All these factors inside the drug are interconnected and interdependent, because they represent different aspects of the mahabhutas of which the drug composed.


CLASSIFICATION OF AYURVEDIC DRUGS

The Ayurvedic drugs comprise vegetable, animal and material products. They can be classified into five categories.


a) Scientifically studied drugs: Some single drugs and compound preparations, for example, Sarpagandha and Yogaraja guggulu, have been studied scientifically and the therapeutic claims made on their behalf have been verified. Sarpagandha is useful for high blood pressure and Yogaraja guggulu for rheumatism.
b) Popular non-toxic drugs: Some Ayurvedic medicines are popular for their therapeutic utility and non-toxic character. One such medicine is Chyavanaprash. Amalaki is the most important ingredient of this medicine which is useful in treating disease of lungs like bronchitis.
c) Effective but toxic drugs: There are some drugs, for example, Bhallatakavaleha, which possesses known therapeutic value but which also produces severe toxicity if used indiscriminately. Bhallataka is the most important ingredient of this medicine which is used in the treatment of chronic and obstinate skin diseases.
d) Drugs for rare use: Some drugs, for example, Shrivishnu taila, though mentioned in Ayurvedic classics, are not in extensive use. Only physicians in certain regions of India use them and recognize their efficiency.
e) Hereditary and patent drugs: Some physicians have specialized in curing certain diseases. The formulae and methods of preparation of the drugs they administer are known only to them, or to the trusted members of their family. While some of the drugs are not effective as the claims made for them, some others are found to be very effective. In most cases, the physicians do not agree to disclose the formula.