Active ingredient

An active ingredient (AI) is the ingredient in a pharmaceutical drug or pesticide that is biologically active. The similar terms active pharmaceutical ingredient (API) and bulk active are also used in medicine, and the term active substance may be used for natural products. Some medication products may contain more than one active ingredient. The traditional word for the API is pharmacon or pharmakon (from Greek: φάρμακον, adapted from pharmacos) which originally denoted a magical substance or drug. The dosage form for a pharmaceutical contains the active pharmaceutical ingredient (API), which is the drug substance itself, and excipients, which are the ingredients of the tablet, or the liquid the API is suspended in, or other material that is pharmaceutically inert. Drugs are chosen primarily for their active ingredients.During formulation development, the excipients are chosen carefully so that the active ingredient can reach the target site in the body at the desired rate and extent. In phytopharmaceutical or herbal medicine, the active ingredient may be either unknown or may require cofactors in order to achieve therapeutic goals. This leads to complications in labelling. One way manufacturers have attempted to indicate strength is to engage in standardization to a marker compound. However, standardization has not been achieved yet: different companies use different markers, or different levels of the same markers, or different methods of testing for marker compounds. For instance, St John's wort is often standardized to the hypericin which is now known not to be the 'active ingredient' for antidepressant use. Other companies standardize to hyperforin or both, although there may be some 24 known possible active constituents. Many herbalists believe that the active ingredient in a plant is the plant itself.