Potential problems when switching from one excipient to another in drug formulation

Excipients are used to prepare dosage forms in order to facilitate the admi nistration and the efficacy of drugs through better handling of the manufac turing 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 prepare d with the same excipient (microcrystalline cellulose) but originating from several suppliers may display very dramatic differences: the main differen ce concerns the in vitro, dissolution rate which can consequently affect th e bioavailability. Switching from one excipient to another is still possibl e but the similarity in behaviour of the dosage form must be demonstrated b y relevant tests including functionality tests.