The present technology is directed to compositions comprising d-threo-methylphenidate conjugates and unconjugated methylphenidate. The present technology also relates to compositions and oral formulations comprising d-threo-methylphenidate conjugated to nicotinoyl-L-serine, and/or a pharmaceutically acceptable salt thereof, and unconjugated methylphenidate and/or a pharmaceutically acceptable salt thereof. The present technology additionally relates to a pharmaceutical kit containing the composition comprising d-threo-methylphenidate conjugated to nicotinoyl-L-serine, and/or a pharmaceutically acceptable salt thereof, and unconjugated methylphenidate and/or a pharmaceutically acceptable salt thereof.