Osmolality of Commercially Available Oral Rehydration Solutions: Impact of Brand, Storage Time, and Temperature

Abstract

Oral rehydration solutions (ORS) are specifically formulated with an osmolality to optimize fluid absorption. However, it is unclear how many ORS products comply with current World Health Organization (WHO) osmolality guidelines and the osmotic shelf-life stability is not known. Therefore, the purpose of this investigation was to examine the within and between ORS product osmolality variation in both pre-mixed and reconstituted powders. Additionally, the osmotic stability was examined over time. The osmolality of five different pre-mixed solutions and six powdered ORS products were measured. Pre-mixed solutions were stored at room temperatures and elevated temperatures (31 °C) for two months to examine osmotic shelf stability. Results demonstrated that only one pre-mixed ORS product was in compliance with the current guidelines both before and after the prolonged storage. Five of the six powdered ORS products were in compliance with minimal inter-packet variation observed within the given formulations. This investigation demonstrates that many commercially available pre-mixed ORS products do not currently adhere to the WHO recommended osmolality guidelines. Additionally, due to the presence of particular sugars and possibly other ingredients, the shelf-life stability of osmolality for certain ORS products may be questioned. These findings should be carefully considered in the design of future ORS products.

Keywords: dehydration; electrolytes; euhydration; oral rehydration therapy; rehydration.

Figure 1

Schematic outlining the study methodologies for the third experiment; see text for further details. * The baseline bottle was aliquoted and subsequently stored for sampling at each time point. ^†,¶ A new bottle of each test beverage was also sampled at each time point.

Figure 2

Beverage osmolality for: (a) pre-mixed solutions; and, (b) reconstituted powders. The left y-axis denotes the difference between beverage and WHO-UNICEF osmolality; the right y-axis denotes the absolute beverage osmolality. Each bar represents the median value for the three bottles tested. The variation plotted represents the range. The horizontal dotted lines denote the optimal range for beverage osmolality (200–260 mmol/kg; see text for details).

Figure 3

Impact of time and storage conditions on the osmolality of various pre-mixed oral rehydration solutions [ORS] for: (a) freshly opened bottles stored at room temperature; (b) beverage aliquots stored at room temperature; and, and (c) beverage aliquots stored at elevated temperatures. The shaded area denotes the optimal range for beverage osmolality (200–260 mmol/kg; see text for details).