[The interchangeability of excipient formulations and the eventual consequences].

Excipients are used to prepare dosage forms in order to facilitate the administration and the efficacy of drugs through better handling of the manufacturing process and an increase in the stability of the dosage forms as well. They are produced, as for drugs, by lots and although they correspond to official Pharmacopoeian monographs, they may vary from batch to batch. This can alter the physico-chemical properties as well as their functionalities. Even for classical and non-critical tableting excipients, tablets prepared with the same excipient (microcrystalline cellulose) but originating from several suppliers may display very dramatic differences: the main difference concerns the in vitro dissolution rate which can consequently affect the bioavailability. Switching from one excipient to another is still possible but the similarity in behaviour of the dosage form must be demonstrated by relevant tests including functionality tests.