Rehydration powder is essentially sugar and salts. Specifically, these powders contain glucose, sodium chloride, potassium chloride and disodium hydrogen citrate. Preparations may vary slightly among different brands. Rehydration powder is used to treat dehydration associated with diarrhea, particularly that caused by cholera and rotavirus as it can be prolonged and severe. The powder should be mixed with water as indicated on the label and used within one hour or up to 24 hours if kept in the refrigerator.
In healthy individuals, fluids and electrolytes, especially sodium, are pumped into the intestines as intestinal secretions. These help with digestion and are subsequently reabsorbed, thereby maintaining constant sodium levels. During diarrhea, most of the secreted fluids and salts are not reabsorbed and are lost. Without intervention, this can quickly result in very low sodium levels within the body. According to the "Oxford Handbook of Clinical Medicine," low sodium levels cause headaches, confusion, muscle weakness and cramps and eventually coma.
Importance of Glucose
The role of glucose in rehydration powders is not to provide calories and energy but rather to aid the absorption of sodium. In fact, in order for sodium to be absorbed from the intestines, glucose or galactose need to be present; without them, sodium will not be taken up. As sodium and glucose are absorbed into the intestines, water is drawn in, thereby rehydrating the body. This is why solutions contain glucose and salts are more effective at rehydration than water alone.
Potassium and Chloride
Potassium and chloride are incorporated in rehydration powders because as for sodium, diarrhea can result in large losses of these ions. According to the University of Maryland Medical Center, large losses of potassium can result in weakness, muscle cramps and irregular heartbeat. Chloride is another important electrolyte; low body chloride levels can contribute to and exacerbate dehydration.
You can make a simple rehydration solution at home, as described by the Rehydration Project. Mix 1 liter of water with 8 teaspoons of sugar and 1 teaspoon of salt. Half a cup of orange juice or half of a mashed banana can be added to add potassium. If commercial preparations are available, these should be used as errors in formulations of homemade versions can occur. Sports drinks should not be used to treat diarrhea as often these contain too much sugar, which can irritate the intestines. Antiddiarrheal and antiemetic drugs should only be used in consultation with a doctor.