AFRO-NETS> New WHO ORS formula

[Andy Gray <andy@healthlink.org.za>]

With thanks from E-Drug <e-drug@healthnet.org>

New WHO ORS formula
-------------------

Hi all,

Here is the detail on the ORS issue, promptly supplied by Chris Pow-
ell, WHO Family and Community Health. Tables from the WORD document 
supplied have been altered, preserving the detail, and the reference 
inserted. Anyone care to comment on how this will affect recommenda-
tions for home-prepared ORS?

Regards,

Andy Gray MSc(Pharm) FPS
Senior Lecturer
Dept of Experimental and Clinical Pharmacology
Nelson R Mandela School of Medicine
P Bag 7 Congella 4013
South Africa
Tel: +27-31-260-4334/4298 
Fax: +27-31-260-4338
mailto:graya1@nu.ac.za 
or 
mailto:andy@healthlink.org.za


ORAL REHYDRATION SALTS (ORS) A NEW REDUCED OSMOLARITY FORMULATION

For more than 25 years WHO and UNICEF have recommended a single for-
mulation 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 ef-
fective and without apparent adverse effects in worldwide use. It has 
contributed substantially to the dramatic global reduction in mortal-
ity from diarrhoeal disease during the period.

For the past 20 years, numerous studies have been undertaken to de-
velop an 'improved' ORS. The goal was a product that would be at 
least as safe and effective as standard ORS for preventing or treat-
ing 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 ab-
sorption. 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) in July 2001 (Reduced osmo-
larity oral rehydration salts (ORS) formulation - Report from a meet-
ing of experts jointly organised by UNICEF and WHO. WHO/CAH/01.22; 
http://www.who.int/child-adolescent-
health/New_Publications/CHILD_HEALTH/Expert_consultation.htm ), 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 unsched-
uled supplemental IV therapy in children given this solution was re-
duced 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 glu-
cose (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 os-
molarity 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 solu-
tion, especially for children with acute, non-cholera diarrhoea, WHO 
and UNICEF now recommend that countries use and manufacture the fol-
lowing formulation in place of the previously recommended ORS solu-
tion 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), Glu-
cose, anhydrous (75) Potassium chloride (1.5), Chloride 
(65)/Potassium (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 ac-
ceptable 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 ex-
  ceed 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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