Pharmaceutical compositions comprising Gd-complexes and polyarylene additives

A pharmaceutical composition comprising an adduct consisting of a macrocyclic gadolinium complex (Gd-complex), or a pharmaceutical salt thereof, and a water-soluble polyarylene additive, or a pharmaceutical salt thereof, wherein the Gd-complex is tetraazacyclododecane-based with 3 or 4 carboxylic acid substituents, or a tetrameric derivative thereof, wherein the water-soluble polyarylene additive, or a pharmaceutical salt thereof, comprises 4 carbocyclic fused aromatic rings that are substituted by 2, 3, or 4 hydrophilic substituent groups selected from the group consisting of —OH, —COOH, —SO3H, —OSO3H, and —NH2, wherein the molar ratio of macrocyclic Gd-complex to polyarylene additive ranges from 1:1 to 1:10 (m/m) and wherein the macrocyclic Gd-complex has an association constant Ka for the polyarylene additive of at least 250 M−1.