The present invention concerns a liquid formulation that is stable to oxidation and that is based on paracetamol in an aqueous solvent obtainable by the following steps: (i) dissolving in a reaction vessel paracetamol in an aqueous solvent having a temperature between 65° C. and 95° C., and having pH between 5.0 and 6.0; (ii) cooling the solution so formed to a temperature equal to or above 35° C. and below 40° C. under an atmosphere of nitrogen; (iii) adding cysteine hydrochloride and sodium hydroxide simultaneously to the solution without stirring; (iv) closing the reaction vessel, and stirring the solution of step iii) in a nitrogen atmosphere. It further relates to a method for preparing the formulation.