Composition of ORS:
The fluid lost in diarrhea is isotonic, so both water and electrolytes need to be replaced. Absorption of electrolytes from the gut is an active process (glucose coupled sodium transport: secondary active transport process) that requires energy. Infected mucosa is capable of very rapid fluid and electrolyte absorption if carbohydrate is available as an energy source. So this is why ORS is effective as it contains glucose as the energy source along with water and electrolytes.