Virya in general can be understood as Shakti (power). The virya accounts for the effects of the drug from the time ingestion and as long as it lasts in the body. A substance manifests its actions as soon as it comes in contact with the tongue and as log as it lasts in the body before excretion. According to a famous rishi, Maharishi chakrapani, the substance manifests its actions through its virya only till the vipaka takes place. His position is that rasa comments and its action only during the stage of its contact with the tongue. Just after the action of virya commences and it lasts till the paak (digestion) is over and ultimate action of the drug is seen in its vipaka. The effect of virya of some substances are seen during the stage of initial on that there are two kinds of virya namely ushan (hot) and sheet (cold) virya.
It can be seen that a substance contributes its properties top the body by rasa (rasa) to some extent, by virya (power) to some extent, vipaka by some extent and by prabhavh (action) by some extent. Sometimes, all the first three may fall in one line and thus act homogenously. As an example, draksha fruit (grapes) or milk or ghee has madhur rasa, madhur vipaka and sheet virya, hence homogenous effect of mitigation of vata and pitta is produced. In honey, as seen on the other hand, we find that it is a strong kapha reducing factor, since it undergoes katu vipaka. Honey has madhur and kashaya rasa. As it is madhur rasa, it definitely should increase kapha, but it does not happen. In contrast it reduces kapha. We can here explain this phenomenon so as to katu vipaka. Sometimes, this vipaka in certain substances has favorable effects and in certain instances unfavorable effects. If a substance has rasa, virya, vipaka, all of which have their contributions throughout. If not, they will have different effect, which are not incompatible. Thus pipilli (piper longum) reduces kapha by effect of its rasa as soon as it comes, into contact with the tongue and continues the same kapha suppressing action when its ushan virya (hot potency) but stops its kapha suppressing properties when it undergoes madhur vipaka. On an account of such madhur vipaka, the total effect will be reduction of kapha when it comes into contact with the tongue, continues to do the same still further on account of its ushan virya (hot potency) and katu vipaka. Thus marich (black pepper) is valuable in suppressing kapha more than sunthi (dried ginger) or pipilli (piper longum) but as it causes loss of virility, it is not as valuable as sunthi in these cases where loss of virility is found along with excess of kapha.