A method for the preparation of a bioadhesive compact matrix, which comprises the preparation of a uniform mixture of powders comprising one alkylcellulose or one hydroxyalkylcellulose and a non-water-soluble, water-swellable cross-linked polycarboxylic polymer； the preparation of compressed units starting from such powder mixture by direct compression and finally the heating of the compressed units thus obtained to a temperature in the range of 80 - 250°C for a time of 1-60 minutes； the powder mixture can also comprise at least one active substance and the compressed units thus obtained are characterized by a prolonged release, and have a release kinetics of the active substance substantially of zero order in an aqueous solution at pH 4-8.
