The group of drugs which are less toxic in nature than visha and not so lethal and produces certain toxic symptoms on consumption or administration is called as Upavisha.
The number of upavisha varies in different different samhita.
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Shodhana of Upavisha-
There are various methods are prescribed in samhitas for purification of Upavishas.They are-
1.Gomutra Nimajjana-The visha dravyas soaked in cow’s urine for some prescribed period of time.
2.Swedana-Visha dravyas should boiled for a period of time in different liquids such as cow’s milk,cow’s urine,goat’s milk,vegetables extracts,kanika etc
3.Bharana-frying of visha dravya with ghee or without ghee.
4.Bhavana-Trituration of visha dravya with vegetables extracts
5.Nishshehana-reducing of oily contents
6.Kshalana-washing of visha dravya with hot water