Reduced osmolarity oral rehydration solution for treating cholera.

BACKGROUND: Oral rehydration solution (ORS) is used to treat dehydration caused by diarrheal diseases including cholera. Reduced osmolarity formulations are safe and more effective than standard ORS for treating non-cholera diarrhea. As cholera causes rapid electrolyte loss, it is important to know if these benefits are similar for people with cholera.

OBJECTIVES: To compare the safety and efficacy of reduced osmolarity oral rehydration solution (ORS) with standard ORS for treating diarrhea due to cholera.

SEARCH STRATEGY: We searched the Cochrane Infectious Disease Group Specialized Register (January 2004), CENTRAL (The Cochrane Library Issue 1, 2004), MEDLINE (1966 to January 2004), EMBASE (1974 to January 2004), and LILACS (1982 to January 2004). We also contacted organizations and searched reference lists.

SELECTION CRITERIA: Randomized controlled trials comparing reduced osmolarity ORS with standard ORS for treating adults and children with acute diarrhea due to cholera.

DATA COLLECTION AND ANALYSIS: Two reviewers independently applied eligibility criteria, assessed trial quality, and extracted data. We pooled binary data using relative risks (RR), continuous data using weighted mean difference (WMD) or the standardized mean difference (SMD), and presented the results with 95% confidence intervals (CI).

MAIN RESULTS: For glucose-based reduced osmolarity ORS, seven trials (718 participants) met the inclusion criteria. Biochemical hyponatremia (serum sodium < 130 mmol/L) was more common with reduced osmolarity ORS (RR 1.67, CI 1.09 to 2.57; 465 participants, 4 trials); for severe biochemical hyponatremia (serum sodium < 125 mmol/L) this was not significant (RR 1.58, CI 0.62 to 4.04; 465 participants, 4 trials). No trials reported symptomatic hyponatremia or death. We found no statistically significant difference in the need for unscheduled intravenous infusion. Analyses separating children and adults showed no obvious trends. Two trials also examined rice-based ORS. In the reduced osmolarity group, duration of diarrhea was shorter (WMD -16.85 hours, CI -21.22 to -12.48; 102 participants, 2 trials).

REVIEWERS' CONCLUSIONS: In people with cholera, reduced osmolarity ORS is associated with biochemical hyponatremia when compared with standard ORS, although there are similar benefits in terms of other outcomes. Although this risk does not appear to be accompanied by serious consequences, the total patient experience in existing trials is small. Under wider practice conditions, especially where patient monitoring is difficult, caution is warranted.