The drug is prepared in cold water in a covered container, heated over moderate heat for up to 30 minutes, briefly brought to the boil, poured through a sieve and the still warm herbal residue is squeezed out as much as possible. This process is used for hard, poorly digestible root, shoot and bark parts, otherwise the ingredients cannot be released; well suited e.g. for tormentil root, oak bark. However, drugs that contain essential oils (e.g. valerian root, angelica or lovage root) must not be cooked because the essential oils would escape with the steam. TCM drugs typically require a longer cooking time.
A decoction (Latin decoctum from decoquere "to boil"), decoction or decoction is an aqueous extract obtained by boiling solid drugs.
Already in the pharmacopoeias of the 14th century, decoctions were listed as an (external) liquid medicinal form. In contrast to today's formulations in DAB, the substances used were often macerated before cooking.
Today, decoctions are freshly prepared aqueous extracts made from crushed plant parts, which are poured over with cold water, then heated in a water bath with repeated stirring and then pressed.
Decoctions have always been used worldwide in medicine and phytotherapy.