The present invention relates to a stabilized composition with significantly improved shelf-life stability. More particularly, the present invention relates to a stable liquid aqueous pharmaceutical composition comprising cytisine or a pharmaceutically acceptable salt thereof, at least one antioxidant selected from the group consisting of a sulfite, bisulfite, and metabisulfite compound. The present invention relates also to a use of at least one antioxidant selected from the group consisting of a sulfite, bisulfite, and metabisulfite compound for the stabilization of a liquid aqueous pharmaceutical composition comprising cytisine.