An oral methylphenidate powder which is reconstitutable into a final oral aqueous sustained release formulation containing at least about 50%, or at least about 80% by weight water based on the total weight of the suspension, is provided. The powder is a blend containing a combination of an uncoated methylphenidate-ion exchange resin complex, a barrier coated methylphenidate-ion exchange resin complex-matrix, and a water soluble buffering agent such that upon formed into an aqueous liquid formulation, the formulation has a pH in the range of about 3.5 to about 5, or about 4 to about 4.5. Following administration of a single dose of the oral aqueous methylphenidate suspension, a therapeutically effective amount of methylphenidate is reached in less than one hour and the composition provides a twelve-hour extended release profile.
