Vipaka is one of the 5 qualities of a dravya (substance). Vipaka is the end effect of metabolism. It is related to the rasa of a dravya but manifested only after the dravya comes in contact with the agni i.e. digestive fire in the body. Thus vipaka is that quality of a substance which is associated with rasa of a substance as well as the stage of metabolism or transformation of a dravya after its consumption. It holds specific significance in the field of Ayurvedic pharmacology and dietetics. The action of a dravya inside the body after its metabolism can be understood to some extent if the vipaka of a dravya is known. Every dravya or substance has its own rasa(taste) and when this rasa encounters jatharagni or digestive fire it transforms into vipaka. Rasa undergoes metabolic changes and vipaka is the metabolic end effect of a dravya(substance).
The term 'Vipaka' is composed of 2 parts. वि + पच 
- Vi (वि) : it stanads for Vishista
- Pacha : pacha is the root term of word pachanam meaning digestion and transformation
Thus, The term vipaka indicates the specific transformation of a dravya after its metabolism inside the body. This specific quality generated after transformation is called as 'Vipaka' in Ayurveda. It is defined by Acharya Vagbhata as,
जाठरेणाग्निना योगाद्यदुदेति रसान्तरम् | रसानां परिणामान्ते स विपाक इति स्मृतः ॥ (Asht. Hrud. 9.20)
jāṭhareṇāgninā yogādyadudeti rasāntaram | rasānāṁ pariṇāmānte sa vipāka iti smr̥taḥ ॥ (Asht. Hrud. 9.20)
Meaning: The digestive fire or jatharagni when comes in contact with rasa of a certain dravya or ahara(food) it transforms into vipaka at the end. Thus the end effect of the rasa(taste) can be termed as vipaka.
The concept of Avasthapaka and Nishthapaka
Avasthapaka and nishthapaka are 2 distinct concepts in Ayurveda. Nishthapaka means vipaka while avasthapaka is the substance's quality displayed during the transient phase of digestion. Vipaka is constant quality of a substance post digestion or transformation while, avasthapaka is temporary state. Both of them have effect on body components and health. Avasthapaka is constant irrespective of a dravya whereas nishthapaka or vipaka is specific to the dravya and related to its rasa. Both the terms include 'paka' as a part of their name since both these qualities are dependent on the process of paka i.e. pachanam (digestion and transformation of a substance).
Awasthapaka (initial stage)
When the food is ingested, it undergoes various metabolic changes in our digestive tract, it does not remain in that same state. thus, the process in which the food changes, its state is known as awasthapaak. This occurs in three stages.
- Prathama awasthapaka (first level of initial stage of digestion) wherein the food gets digested and changes its form in aamashaya or stomach with the help if madura(sweet) Rasa. Here kapha is produces which is like froth.
- Dwitiya awasthapaak(second level of initial stage of digestion) wherein the semi digested food leaves the stomach and changes its form further with the help of amla(sour) rasa. Here pitta is produced.
- Trutiya awasthpaak(third level of initial stage of digestion) wherein the food changes its form into solid mass in intestine with the help of katu rasa. Vata is produced in this process.
Nishthapaka or Vipaka (End stage)
Nishthapaka is the term synonymously used with the term vipaka. Vipaka of a dravya is specific to its rasa. Ayurveda treatises clearly explain which rasa generates which vipaka. In general, it is described that,
परं चातो विपाकानां लक्षणं सम्प्रवक्ष्यते ॥
कटुतिक्तकषायाणां विपाकः प्रायशः कटुः | अम्लोऽम्लं पच्यते स्वादुर्मधुरं लवणस्तथा ॥ (Char. Samh. 26.57-58)
paraṁ cāto vipākānāṁ lakṣaṇaṁ sampravakṣyate ॥
kaṭutiktakaṣāyāṇāṁ vipākaḥ prāyaśaḥ kaṭuḥ | amlo'mlaṁ pacyate svādurmadhuraṁ lavaṇastathā ॥ (Char. Samh. 26.57-58)
Meaning: It is the finally transformed state of food or dravya (substance) after digestion. After the initial digestion phase, the food is assimilated for the further nourishment of dhatus in this process. The metabolism of any dravya in this context is based on rasa(taste) since it can be perceived, but their end effect can only be inferred by their actions in our body. On this basis vipaka can be understood as follows.
Substances having Katu (कटुः| Pungent), Tikta (तिक्त | Bitter), Kashaya (कषाय | Astringent) rasa are transformed into katu vipaka.
Substances having Amla (अम्ल | Sour) rasa are transformed into Amla vipaka and those having Madhura (मधुर | Sweet) and Lavana (लवण | Salty) rasa are transformed into madhura vipaka.
But there exists a set of certain drugs which have an unexpected end effect or vipaka in our body according to some ayurvedic scholars.
Types of Vipaka
According to ayurvedic acharyas (scholars) there is difference of opinion and theories when it comes to the classification of vipaka. But at the tip of iceberg the types are as follows,
- Shadvidha vipaka vada (concept of 6 vipaka) 
- Panchavidha vipaka vada (concept of 5 vipaka) 
- Trividha vipaka vada (concept of 3 vipaka)  
- Dvividha vipaka vada (concept of 2 vipaka) 
Despite differences of opinions regarding types of vipakas, widely the theory of 3 types of vipakas is accepted and applied in to practice. According to this theory, MAdhura, Amla and Katu are 3 types of vipakas for various dravyas based on their rasa.
Action and effect of Vipaka on body
Vipaka is directly associated to the rasa of a dravya. Similar to rasa, vipaka also affects body components and their function. The effect of each of the 3 vipakas on doshas in body is given in table.
|Sr No||Vipaka type||Effect on Dosha|
|2||Amla||Increases Pitta and Kapha|
Importance of Vipaka
While selecting food and medicinal substances, vipaka of a certain food article or medicinal substance is taken in to consideration along with other factors like rasa, veerya, guna etc. Viapaka is one of those factors that decide action of a dravya inside body and its health effects. Moreover, the concept of vipaka is important to Ayurveda because the guna (benefits) and dosha (adverse effects) of dravya are dependent on the end effect of metabolism that is vipaka since vipaka can directly affect dosha equilibrium. Also, if a certain drug is digested with the help of proper jatharagni (digestive fire) then the guna (property) of that drug is enhanced, whereas if there is no proper digestion of that drug then dosha imbalance can be seen due to inappropriate vipaka.
- Shabdakalpadruma See Vipaka
- Ashtanga Hrudayam (Sutrasthanam Adhyaya 9 Sutra 20)
- Charaka Samhita (Chikitsasthanam Adhyaya 15 Sutra 9 -11)
- Chakrapani commentary on Charaka Samhita (Chikitsasthanam Adhyaya 15 Sutram 9-11)
- Charaka Samhita (Sutrasthanam Adhyaya 26 Sutram 57-58)
- Sushruta Samhita (Sutrasthanam Adhyaya 40 Sutra 10)
- Sushruta Samhita (sutrasthanam Adhyaya 26 Sutra 524)
- Charaka Samhita (Sutrasthanam Adhyaya 26 Sutra 63)
- Ashtanga Hrudayam (Sutrasthanam Adhyaya 1 Sutra 17)