For more
than 25 years WHO and UNICEF have recommended a single formulation of
glucose-based Oral Rehydration Salts (ORS) to prevent or treat dehydration from
diarrhoea irrespective of the cause or age group affected. This product, which
provides a solution containing 90 mEq/l of sodium with a total osmolarity of 311
mOsm/l, has proven effective and without apparent adverse effects in worldwide
use. It has contributed substantially to the dramatic global reduction in
mortality from diarrhoeal disease during the period.
For the past 20 years, numerous studies have been undertaken to develop an
'improved' ORS. The goal was a product that would be at least as safe and
effective as standard ORS for preventing or treating dehydration from all types
of diarrhoea but which, in addition, would reduce stool output or have other
important clinical benefits. One approach has consisted in reducing the
osmolarity of ORS solution to avoid possible adverse effects of hypertonicity on
net fluid absorption. This was done by reducing the solution's glucose and salt
(NaCl) concentrations .
Studies to evaluate this approach were reviewed at a consultative technical
meeting held in New York (USA) and technical recommendations were made to WHO
and UNICEF on the efficacy and safety of reduced osmolarity ORS in children with
acute non-cholera diarrhoea, and in adults and children with cholera.
These studies showed that the efficacy of ORS solution for treatment of children
with acute non-cholera diarrhoea is improved by reducing its sodium
concentration to 75 mEq/l, its glucose concentration to 75
mmol/l, and its total osmolarity to 245 mOsm/l. The need for unscheduled
supplemental IV therapy in children given this solution was reduced by 33%. In a
combined analysis of this study and studies with other reduced osmolarity ORS
solutions (osmolarity 210-268 mOsm/l, sodium 50-75 mEq/l) stool output was also
reduced by about 20% and the incidence of vomiting by about 30% 1. The 245 mOsm/l
solution also appeared to be as safe and at least as effective as standard ORS
for use in children with cholera.
The reduced osmolarity ORS containing 75 mEq/l sodium, 75 mmol/l glucose (total
osmolarity of 245 mOsm/l) is as effective as standard ORS in adults with
cholera. However, it is associated with an increased incidence of transient,
asymptomatic hyponatraemia. This reduced osmolarity ORS may be used in place of
standard ORS for treating adults with cholera, but careful monitoring is advised
to better assess the risk, if any, of symptomatic hyponatraemia.
Because of the improved effectiveness of reduced osmolarity ORS solution,
especially for children with acute, non-cholera diarrhoea, WHO and UNICEF now
recommend that countries use and manufacture the following formulation in place
of the previously recommended ORS solution with a total osmolarity of 311 mOsm/l.
Reduced osmolarity ORS:
ingredient |
(grams/litre) |
ion |
(mmol/litre) |
Sodium chloride |
2.6 |
Sodium |
75 |
Glucose, anhydrous |
13.5 |
Glucose, anhydrous |
75 |
Potassium Chloride |
1.5 |
Chloride/Potassium |
65/20 |
Trisodium
Citrate,dihydrate |
2.9 |
Citrate |
10 |
Total
Osmolarity = 245
Although this single ORS formulation is recommended, WHO and UNICEF have
previously published criteria, which remain unchanged, for acceptable ORS
formulations. These criteria are listed below; they
specify the desired characteristics of the solution after it has been prepared
according to the instructions on the packet:
* The total substance concentration (including that contributed by glucose)
should be within the range of 200-310 mmol/l.
* The individual substance concentration:
- Glucose - should at least equal that of sodium but should not exceed 111 mmol/l
- Sodium - should be within the range of 60-90 mEq/l
- Potassium - should be within the range of 15-25 mEq/l
- Citrate - should be within the range of 8-12 mmol/l
- Chloride - should be within the range of 50-80 mEq/l
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