Disclosed is a modified release pharmaceutical composition comprising rhein (4,5-dihydroxy-9,10-dioxoanthracene-2-carboxylic acid, Formula I) or diacerein (diacetylrhein, 4,5-diacetyloxy-9,10-dioxo-anthracene-2-carboxylic acid, Formula II), or salts or esters thereof, wherein the modified release comprises combination of extended release or delayed release with immediate release. The modified releases are achieved by one or more functional coatings or mixing the rhein or diacerein, or salts or esters thereof with one or more pharmaceutically acceptable polymers, wherein the composition exhibits a dissolution profile such that more than 70% of diacerein is released within 60 minutes, wherein the release rate is measured in Apparatus 2 (USP, Dissolution, paddle, 75 rpm) using 1000 ml of pH 5.7 phosphate buffer at 37°C ± 0.5°C. Also disclosed is a process for preparing a modified release composition by combining rhein or diactylrhein with one or more pharmaceutically acceptable polymers, optionally with other pharmaceutical excipients and converting the mixture into a suitable dosage form.
