The significant role of Agni in relation to digestion and metabolism has been explicitly described in Ayurveda. All the substances whether dietetic or medicinal are ingested so as to make them assimilable after proper digestion. The medicines are broken down and resynthesized during the process of digestion and metabolism. The resynthesis may be in the original form of the drug or otherwise. This is why the question of Samanapratyayarabdha and Vichitrapratyayarabdha find relevance to Vipaka. The site and area of Vipaka extend from Koshta to the Dhatus.
Unlike the Rasa, the actions of Vipaka are to be taken in to account (Vipaka Karma Nishtaya) and the site of these actions have been described to be at the level of Koshta or at the level of the Dhatus. But then, again, the actions generally ascribed to the Vipakas are explained on the basis of Gunas only.
Let us remind ourselves of the same situation with the rasas also. If the actions of Vipaka are to be explained at the level of Koshta, it is the Snigdha – Ruksha qualities which play their part and this is why Madhura and Amla Vipakas are said to induce smooth evacuation of stool and urine while the Katu Vipaka does the reverse. But when the actions of Vipaka are to be
Basic concepts of Ayurvedic pharmacology 111 explained at the level of the Dhatus, Guru & Laghu qualities play their part and this is why Madhura Vipaka increases the Dhatus while Amla and Katu Vipakas reduce them. This shows that either due to the change of site or the body element, or change in the chemical constitutions in the drug, different qualities come into action at different places. Looking at this whole from the angle of Virya, the Ashtavida Viryavada includes Snigdha –Ruksha qualities which go to explain the action of Vipaka at the Koshta level. One is reminded here of the version about the Virya which reads Viryam Yavat Adhivasat Nipatat Cha Upalabhyatae. The word ‘Nipata’ is related to Rasa on one side and the Virya on the other. Similarly the word ‘Adhivas’ is related to Vipaka on one side and the Virya on the other and, therefore, the words falling in the jurisdiction of qualities have been used to explain the actions of Rasa and Vipaka. These same qualities have been included in Ashtavidha Viryavada. The idea behind this is probably to explain the structure – function relationship with reference to the specific site of action and special affinity to a particular body element. If we are asked to fix up limitations and jurisdictions of these terms we would prefer to use the word
‘Rasa’ for its chemical structure causing certain local actions at the level of the tongue by virtue of Mrudu –Tikshna Viryas; and the ‘Vipaka’ to indicate the changes in the chemical structure of the drug in the digestive and metabolic processes and to confine the actions of Vipaka in the Koshta only so as to explain them with Snigdha – Ruksha Viryas. After the drug is absorbed it has to be picked up by the receptors in the specific body element or Dhatus on the qualitative similarity and, therefore, we would prefer to correlate other actions on the Dhatus with Gunas as enumerated in Rasapanchak.
Basic concepts of Ayurvedic pharmacology 112 GUNA VIS A VIS DRUG ACTION
There is no doubt about the fact that in the ultimate analysis the stimulation or depression corresponding to Vriddhi and Kshaya of the Dhatus are the two main resultant states after the drug administration. In fact in a general summary the actions have been divided in to Vriddhi and Kshaya only. The comprehensive and critical analysis of the stages of pathogenesis and the events envolved in them very clearly indicate that the Doshas are generally brought down to normal while the Dhatus are generally pulled up to normal. This is because of the fact that on a very general observation it has been proved that the Dosha Vrinddhi and Dhatu Kshaya are the resultant states of the disease –causing conditions. In view of this Ayurvedic medicine, generally speaking, depresses the Doshas and stimulates the Dhatus only in abnormal conditions. The Vriddhi and Kshaya can better be appreciated qualitatively rather than quantitatively. Let us postulate a view here that the structure – function relationship, in ayurvedic paralance, indicate the inheritance of the permanent qualities of the components. In view of this there should have been only two qualities ascribed to each Rasa, for only two predominant proto elements constitute one Rasa. But the texts have ascribed three qualities to one Rasa. The idea behind it is that the specific combination of the two proto elements originating a specific Rasa carry with them individual qualities as well as engender a specific quality also. This specific quality is of biological significance as the biotransformation in relation to the stimulation and depression of the body element relates to the third quality engendered by the combination of the two specific elements in Rasa. Obviously the Madhura Vipaka is said to be Guru while Amla and Katu Vipaka are said to be Laghu and their actions at Dhatu level are explainable on the basis of these two
Basic concepts of Ayurvedic pharmacology 113 qualities. It is, therefore, postulated that the words Guru and Laghu fall under the jurisdiction of Gunas as enumerated in the Rasapanchak. Since the comprehensive term Virya includes all actions at all levels the Guru and Laghu finds Place in Ashtavidha Virya vada. Each Dhatu is endowed with its specific Agni and the drug is treated with these Agnis before it exerts the influence on the Dhatus. This is what is mean by ‘Yatra Kurvanti tat Adhikaranam’. If the Vriddhi and Kshaya are to be explained on the basis of similars and dissimilars the biotransformation of the substances by concerned Dhatwagnis becomes imperative. So far, from the point of view of comprehensive term Virya a relationship is established between Rasa and Mrudu – Tikshna Virya, Vipaka and Snigdha – Ruksha Virya, Guna and Guru – Laghu virya and this completes six Viryas included in Ashtavidha Viryavada. The remaining two Viryas I.e. Sheeta and Ushna demand a special mention and clarification.
VIRYA VIS – A – VIS SPECIFIC THERAPEUTIC ACTION IN