Arka kalpana is the famous kalpana explained in Bhaishajya Kalpana but according to Arka Prakash it is considered one among the Panchavidha kashay kalpana and is said to be the most potent. It is introduced in ayurvedic pharmacy in later part of Samhita period , which is very specific in its mode of preparation and therapeutic effect. Arka Prakash is the first ayurvedic classical text in which various kinds of distillation procedures and heating methods are mentioned for preparing Arka from different types of dravya for different disease. Arka is a unique preparation in which the water soluble active principles from herbal drugs are extracted through distillation method. The five basic kalpanas comprise of Swarasa (Juice), Kalka(Paste), Kwath(Decoction), Hima(Cold infusion) and Phanta(Hot infusion). But some Acharya has variable opinions in the respective formulary classification. According to Arka Prakash, the Panchavidha Kalpanas include Kalka, Choorna, Rasa, Taila and Arka. Due to its increased potency, reduced dose, better shelf Life, easy absorption, fast action and patient compliance, Arka Kalpana is first choice of growing demand among current population.
Sharir Sthaulyakar Arka is one among Arka preparation explained in the text Arka Prakash. It is indicated in Karshya Vyadhi. It contents Ashwagandha, Gokshura, Twaka, Vatakand, has action of Sthaulyakar. In the preparation of Arka the ratio of water varies based on the hardness and form of the drug. The pharmaceutical aspects regarding this formulation have been explained in detail with specific importance to the Yantras, Agni and different method of preparation based on the consistency of Dravyas.