Biopharmaceutical characterisation of herbal medicinal products: are in vivo studies necessary?

Herbal medicinal products have to meet comparable standards concerning the assessment of efficacy, safety and (bio)pharmaceutical quality as chemically defined synthetic drugs. However, these requirements are not fulfilled for many herbal products so far, particularly regarding in vitro dissolution and in vivo bioavailability. The necessity of in vivo studies for a biopharmaceutical characterisation of the products depends on the solubility/permeability properties of the active drug ingredient as well as dissolution behaviour of the dosage form. Also, in the case of herbal medicinal products, a waiver of in vivo BA/BE studies is recommended as long as the active ingredient is highly soluble according to the Biopharmaceutics Classification System and dissolution of the dosage form takes place rapidly (>85%/20 min) in physiological buffer systems (pH 1-8).