INFLUENCE OF TABLET FORMULATION AND SIZE ON THE IN-VITRO SUSTAINED-RELEASE BEHAVIOR OF METOPROLOL TARTRATE FROM HYDROPHILIC MATRICES

Metoprolol tartrate sustained-release tablets were manufactured in 2.8 , 7.0 and 10.0 mm diameters. In order to achieve the sustained release of active ingredients, the hydrophilic cellulose polymers methylcellu lose, hydroxypropylcellulose and sodium carboxymethylcellulose were us ed either alone or in combination. It was investigated, in particular, whether the mini-tablets encased in hard gelatine capsules as multipl e units allow for the sustained release of the basic active ingredient , which is highly soluble in the acidic pH. While a sustained release is possible from the 7.0 and 10.0 mm diameter tablets formulated on th e basis of HPC and NaCMC mixtures, tablets with 2.8 mm diameter do not allow for an adequate control of metoprolol tartrate release during t he gastrointestinal passage. Active ingredient release in the range of up to 80 % release and the tablet surface area above a minimum of app roximately 300 mm(2) are correlated in a linear manner.