Abstract: The invention provides an aqueous pharmaceutical solution for use in the treatment of diseases of the central nervous system (CNS), the solution comprising at least 5 mg/ml dissolved levodopa, and having a pH in the range of 3.0 to 8.5. Said solution is provided by mixing a) an aqueous stock solution comprising levodopa, said stock solution having a pH of less than 2.8 at 25° C. and b) an aqueous buffering solution, for increasing the pH of said stock solution, said buffering solution having a pH of at least 4.0 at 25° C. The aqueous pharmaceutical solution is administered to a subject suffering from a disease of the central nervous system (CNS) shortly after mixing of the aqueous stock solution and the aqueous buffering solution. Furthermore, the invention provides a kit for administration of aqueous pharmaceutical solutions to subjects suffering from diseases of the central nervous system (CNS).