the present invention relates to a formulation containing mesalazine in a stable form , obtained by coating the starting core with a first membrane in non - aqueous solution ; said core containing mesalazine at a high concentration , greater than 90 %, obtained by producing starting cores with active substance content greater than 97 %. the formulation according to the present invention containing mesalazine with specific release in the colon ; in particular the capsule formulation containing 500 mg of mesalazine with specific release in the colon .