The present invention relates to improved formulations of Levosimendan for pharmaceutical use, and particularly for intravenous administration as infusion or injection and of infusion concentrates. The present invention therefore relates to pharmaceutical compositions comprising Levosimendan, in which Levosimendan is present in a solubilized form. The formulations have therapeutically and commercial useful concentrations of Levosimendan. The solutions of the invention have enhanced ability at physiological pH (pH 7.4) and are particular useful as infusion or injection solutions or infusion concentrates. The composition according to the present invention can also be spray-dried or lyophilized to obtain a dried powder which is very stable and which powder forms the original solution after reconstitution in water or an aqueous solvent. Levosimendan or (?)-[[4-(1, 4, 5, 6-tetrahydro-4-methyl-6-oxo-3-pyridazi-nyl)phenyl]hydrazono]propanedinitrile is useful in the treatment of congestive heart failure.