a coating ensuring the controlled release of a biological active ingredient , which can be incorporated in the coating or is surrounded thereby , consists of a varnish - forming polymer selected from the group which consists of cellulose triacetate containing polyethylene glycol as an emollient and vinyl chloride - vinyl acetate copolymer with glycerol as an emollient , and an aqueous phase dispersed in the polymer and consisting of particles of a diameter up to 20 microns , the aqueous phase making up 2 % to 30 % of the volume of the coating . the active ingredient is preferably a pharmaceutical agent affecting the circulatory system or a psychotropic agent .