Glycine-based oral rehydration solution: reassessment of safety and efficacy

The effect of oral rehydration solution and recommended home fluids on diarrhoea mortality

Background Most diarrhoeal deaths can be prevented through the prevention and treatment of dehydration. Oral rehydration solution (ORS) and recommended home fluids (RHFs) have been recommended since 1970s and 1980s to prevent and treat diarrhoeal dehydration. We sought to estimate the effects of these interventions on diarrhoea mortality in children aged <5 years.

Methods We conducted a systematic review to identify studies evaluating the efficacy and effectiveness of ORS and RHFs and abstracted study characteristics and outcome measures into standardized tables. We categorized the evidence by intervention and outcome, conducted meta-analyses for all outcomes with two or more data points and graded the quality of the evidence supporting each outcome. The CHERG Rules for Evidence Review were used to estimate the effectiveness of ORS and RHFs against diarrhoea mortality.

Results We identified 205 papers for abstraction, of which 157 were included in the meta-analyses of ORS outcomes and 12 were included in the meta-analyses of RHF outcomes. We estimated that ORS may prevent 93% of diarrhoea deaths.

Conclusions ORS is effective against diarrhoea mortality in home, community and facility settings; however, there is insufficient evidence to estimate the effectiveness of RHFs against diarrhoea mortality.

Animal and human models for studying effects of drugs on intestinal fluid transport in vivo

The understanding of the physiology and pathophysiology of intestinal fluid transport has been derived from animal and human models of normal and perturbed intestines. This understanding helped in designing drugs and changing the composition of oral rehydration solutions in a targeted manner to affect intestinal fluid absorption/secretion that was tested both in vitro and in vivo before embarking on clinical trials. In this review, in vivo techniques used to study water transport in both animal and human models are described. In particular, steady state intestinal perfusion techniques, closed segment techniques, fistulous animal models, balance study models, enteropooling models, and isotope tracer models are reviewed. Advantages and drawbacks of each technique and examples where drug effects have been studied in a particular model are provided.

Assessment of the safety of glutamine and other amino acids

Glutamine is used to supplement intravenous and enteral feeding. Although there have been many human studies of its efficacy, there have been very few studies with safety as a primary goal. This article analyzes the literature on the safety of glutamine and also examines the available information on high intakes of total protein and other amino acids, so that additional indicators of potentially adverse effects can be suggested. Four studies that specifically addressed glutamine safety were identified, from which it was concluded that glutamine is safe in adults and in preterm infants. However, the published studies of safety have not fully taken account of chronic consumption by healthy subjects of all age groups. To help identify potential undetected hazards of glutamine intake, the literature on adverse effects of high dietary intake of protein and other amino acids was examined. High protein is reputed to cause nausea, vomiting and ultimately death in adults, and has been shown to result in neurological damage in preterm infants. Individual amino acids cause a variety of adverse effects, some of them potentially fatal, but neurological effects were the most frequently observed. Because glutamine is metabolized to glutamate and ammonia, both of which have neurological effects, psychological and behavioral testing may be especially important.

Reduced osmolarity oral rehydration solution for treating dehydration caused by acute diarrhoea in children

BACKGROUND

Oral rehydration solution (ORS) has reduced childhood deaths from diarrhoea in many countries. Recent studies suggest that the currently recommended formulation of ORS recommended by the World Health Organization (WHO) may not be optimal, and solutions that contain lower concentrations of sodium and glucose may be more effective.

OBJECTIVES

In children with acute diarrhoea, to compare reduced osmolarity glucose-based oral rehydration salt solution with international WHO formulation.

SEARCH STRATEGY

The Cochrane Collaboration Trials Register, MEDLINE, and EMBASE were searched. Additional trials were identified by hand searching. Content experts were contacted.

SELECTION CRITERIA

Randomised controlled trials comparing reduced osmolarity ORS solution with the WHO formulation. Outcomes sought were unscheduled intravenous fluid infusion therapy and measures of clinical illness.

DATA COLLECTION AND ANALYSIS

Data were extracted by two reviewers. We tested for heterogeneity using the chi-square statistic, conducted sensitivity analysis by allocation concealment, and the regression approach to assess funnel plot asymmetry from selective trial publication.

MAIN RESULTS

The primary outcome was reported in 12 trials. In a meta-analysis of nine trials, reduced osmolarity ORS was associated with fewer unscheduled infusions compared with standard WHO ORS (Mantel Haenzel odds ratio 0.61, 95% confidence interval 0.47 to 0.81) with no evidence for heterogeneity between trials. No unscheduled intravenous fluid infusion therapy was required in any participant in three trials. Thirteen trials reported stool output, and data suggested less stool output in the reduced osmolarity ORS group. Vomiting was less frequent in the reduced osmolarity group in the six trials reporting this. Six trials sought hyponatraemia, with events in three studies, but no obvious difference between the two arms.

REVIEWER'S CONCLUSIONS

In children admitted to hospital with diarrhoea, reduced osmolarity ORS when compared to WHO ORS is associated with fewer unscheduled intravenous infusions, smaller stool volume post randomisation, and less vomiting. No additional risk of developing hyponatraemia when compared with WHO ORS was detected.

Rotavirus infections: guidelines for treatment and prevention

The classification of rotaviruses as well as the pathogenesis and the diagnosis of rotavirus infections are briefly reviewed. Treatment of rotavirus disease consists mainly of oral or intravenous rehydration, using World Health Organization-recommended oral rehydration solutions or lactated Ringer's solutions, respectively. Specific antivirals have been tried in animal models but are not used for human treatment at present. The epidemiology of rotaviruses is complex as at any one time and in any geographical area different types co-circulate. The development of rotavirus candidate vaccines is reviewed, one of which, the tetravalent, rhesus rotavirus-based human reassortant vaccine, was licensed for universal use in the US in 1998. Its implementation requires careful surveillance of co-circulating rotavirus types (molecular epidemiology) as well as of any potential adverse effects not previously detected.

New causes and treatments for infectious diarrhea in children

Infectious diarrhea is a universal and important health problem in the pediatric population. An expanding number of potential viral, bacterial, and parasitic pathogens have been associated with diarrheal disease. However, the epidemiologic association of a microorganism with diarrhea is only one step in the process of identifying new pathogens. Once the virulence mechanisms of these organisms are elucidated, a causal relationship can be more readily defined. This article reviews the etiologic agents of diarrhea in the pediatric population and focuses on the newer treatment and prevention modalities, including probiotics and vaccinations, which are used increasingly to combat these diseases.

Enhancing clinical efficacy of oral rehydration therapy: is low osmolality the key?

Many empirical clinical trials have used complex carbohydrate as substrate in oral rehydration solutions (ORSs) instead of glucose and have shown a number of important clinical benefits. Foremost among these are reduced stool volumes, shorter duration of diarrheal illness, and lower ORS intake. The underlying mechanisms to explain this clinical advantage have not been fully established, but a number of possible factors have been proposed: (1) increased substrate availability, (2) a "kinetic advantage" for glucose absorption by glucose polymer, (3) differential handling of glucose monomer and polymer by the small intestine, (4) low osmolality, (5) a separate effect of peptides and amino acids on solute-linked sodium absorption, (6) an antisecretory moiety in rice, and (6) enhanced mucosal repair and regeneration by luminal nutrients. In this report, we assess the relative contribution of these factors using evidence from laboratory-based studies, mainly in disease-related intestinal perfusion systems in animals and humans, and the relevant clinical studies available to date. We advance the hypothesis that of all the possible mechanisms proposed to underlie the enhanced clinical efficacy of complex carbohydrate ORSs, their hypotonicity plays the dominant role. If confirmed, this concept could guide future development of glucose and complex carbohydrate-based ORSs.

Electrolyte fluxes in the gut and oral rehydration solutions

This article provides a brief overview of the normal physiology of water and electrolyte fluxes across the gut as a prerequisite for understanding the pathologic disturbances occurring with diarrheal illnesses. In turn, the rationale for the use of oral rehydration solutions in diarrheal disorders is explored.

Alanine- and glucose-based hypo-osmolar oral rehydration solution in infants with persistent diarrhoea: a controlled trial

To evaluate the efficacy of a hypo-osmolar and a standard (World Health Organization) oral rehydration salt (ORS) solution in persistent diarrhoea, a randomized controlled clinical trial was conducted in 55 children. After a 1-day observation period the children were assigned to one of three solutions: standard ORS (WHO-ORS) (osmolality 311 mosmol/l), hypo-osmolar ORS containing L-alanine and glucose (osmolality 255 mosmol/l) and i.v. polyelectrolyte solutions (osmolality 293 mosmol/l) for ongoing replacement of stool loss for the next 4 days. Excellent acceptability of ORS (101-160 ml/kg body weight/day) by the children was observed. There were no significant differences in the total intake of solutions and food, and frequency of stools among the groups. Stool outputs were significantly less in infants receiving hypo-osmolar ORS than in those receiving WHO-ORS for 0-24 h (p = 0.04), 0-48 h (p = 0.01), 0-72 h (p = 0.04) and 0-96 h (p = 0.03). The results indicate a sufficient scope of ORS practice in persistent diarrhoea. Furthermore, we found that a hypo-osmolar ORS containing L-alanine and glucose is as efficacious as an iv solution and more effective than WHO-ORS for replacement of ongoing stool loss in persistent diarrhoea.

Hydrolyzed lactalbumin-based oral rehydration solution for acute diarrhoea in infants

The addition of different organic substrates to standard glucose oral rehydration solution (G-ORS) has been shown to improve the intestinal absorption of sodium and water, and thereby decrease stool losses. Therefore, we evaluated, in infants with acute diarrhoea, the safety and efficacy of three oral rehydration solutions (ORS) which had the same concentrations of electrolytes (with sodium 60 mmol/l) but different substrates of proteins and carbohydrates. One solution (LAD-ORS) contained hydrolyzed lactalbumin (LAD) with maltodextrin and sucrose, a second (MS-ORS) was identical but without LAD and a third (G-ORS) was standard glucose ORS. The three solutions were compared in a double-blind, randomized trial in 74 hospitalized well-nourished children in Panama and the United States. All three oral rehydration solutions were equally efficacious and safe in these children, 54% of whom were infected with rotavirus. There was no suggestion that hydrolyzed lactalbumin or maltodextrin provided any advantage over glucose-ORS in terms of stool output or in duration of diarrhoea. We conclude that all three solutions are efficacious in the therapy of acute diarrhoea in infants.

Oral rehydration therapy

Oral rehydration therapy (ORT) with glucose-electrolyte solutions has been considered to be one of the greatest therapeutic advances of this century. ORT is effective in acute diarrheal disease of diverse etiology. The most widely used oral rehydration solution (ORS) worldwide is that recommended by the World Health Organisation (Na 90, K 20, glucose 111 and citrate 10 mmol/L). Attempts to improve the efficacy of ORS have been made by using complex substrates (rice and other cereals) in place of glucose, and by reducing osmolality by decreasing glucose and sodium concentrations in monomeric ORS. ORS may have wider applications in the management of patients with the short bowel syndrome and in post-surgical patients.

Rehydration and nutritional management

Diarrhoea remains a leading worldwide cause of morbidity and mortality. In developing countries alone, 1.5 billion episodes of diarrhoea occur per year in children under 5 years of age and approximately 4,000,000 of these result in death. Early, appropriate therapy decreases the risk of complications and death due to diarrhoea. Regardless of the causative agent, oral rehydration and nutritional management are the mainstays of good management of infants, children and adults with diarrhoea. Diarrhoeal disease control programmes throughout the developing world have adopted the WHO case management plan as a standard. In this chapter, we review the history, successes and shortcomings of various oral rehydration therapies and recommend a case management approach that is similar to the WHO plan. Although ORT is safe, effective, convenient and economical, this therapy has not been universally implemented in health care settings. The challenge for clinical and public health practitioners in developing and developed countries is to identify and overcome the barriers that exist so that all patients with diarrhoea will have the opportunity to receive optimal care.

Water and solute absorption from a new hypotonic oral rehydration solution: evaluation in human and animal perfusion models

Controversy continues regarding the optimal composition of glucose electrolyte oral rehydration solutions for the treatment of acute diarrhoea. Four perfusion models (normal human jejunum, normal rat small intestine, cholera toxin treated secreting rat small intestine and rotavirus infected rat small intestine) have been developed and used to compare the efficacy of a hypotonic oral rehydration solution with standard United Kingdom British National formulary and developing world oral rehydration solutions (WHO). Despite obvious physiological and pathophysiological differences between these models there was general congruence in the water and solute absorption profiles of the different oral rehydration solutions. Hypotonic oral rehydration solution promoted significantly greater water absorption than other oral rehydration solutions in all rat models (p < 0.001) but apparently increased water absorption failed to achieve significance in human jejunum. British National Formulary-oral rehydration solution was unable to reverse net water secretion in both rotavirus and cholera toxin models. Net sodium absorption from hypotonic and WHO-oral rehydration solutions was significantly greater than from the low sodium British National Formulary-oral rehydration solutions (p < 0.001) except in the rotavirus model when absorption was similar to hypotonic-oral rehydration solutions. These findings show that there is agreement in the apparent efficacy of oral rehydration solutions in these animal and human perfusion models, and that improved water absorption with adequate sodium absorption may be achieved by reducing oral rehydration solution osmolality.

Dominant role for osmolality in the efficacy of glucose and glycine-containing oral rehydration solutions: studies in a rat model of secretory diarrhoea

The effect of osmolality on the efficacy of oral rehydration solutions (ORS) and the contribution of the amino acid glycine to water absorption from ORS have been studied in an animal model of secretory diarrhoea. After exposure to pure cholera toxin, rat small intestine (excluding the duodenum) was perfused in situ with seven different ORS. All ORS were derived from a "basic" solution containing Na 50, K 25, Cl 75 and glucose 50 mmol/l to which 25 or 50 mmol/l of glycine, glucose, or mannitol was added. All ORS reversed water secretion to absorption, but maximum water absorption was obtained with the "basic" solution with an osmolality of 200 mOsm/kg. When the osmolality of the "basic" solution was raised to 225 and 250 mOsm/kg by adding mannitol, water absorption decreased. At each of these osmolalities, substitution of mannitol by glycine or glucose resulted in similar increases in water absorption, but all modifications compared unfavourably with the "basic" solution. Net sodium secretion occurred with all ORS tested, despite net water absorption. These findings in a perfusion model of rat small intestine suggest that osmolality is a key factor influencing the efficacy of ORS and that addition of a second substrate, such as glycine, has no beneficial effects. Our results suggest that there is a maximal rate for water absorption from the small intestine which is inversely related to the osmolality of the perfusate.

Alanine-based oral rehydration therapy for infants with acute diarrhea

Twenty male infants less than 1 year of age with acute diarrhea and dehydration were randomly assigned to a study group and studied in blind fashion in a metabolic unit to assess the efficacy of the addition of 30 mmol/L alanine to the standard World Health Organization (WHO) oral rehydration solution (ORS). Patients were exclusively rehydrated with one of two types of ORS during the first 24 hours of treatment. On the second day, oral feedings were started with a lactose-free formula, and ORS was given to replace stool losses. Body weight, ORS, food intake, vomitus, stool, and urine output were recorded at 6-hour intervals. Blood was drawn at the time of admission, after rehydration, and at 24 and 48 hours of hospitalization to monitor blood gases and electrolytes. Rehydration was satisfactory in both groups of patients. ORS that contained alanine did not reduce the purging rates of the infants compared with those who received standard ORS. Clinically no adverse effect of the alanine-based ORS was observed during hospitalization. None of the patients had significant hypernatremia or hyponatremia, and serum amino acid levels were not altered. These data show that the addition of 30 mmol/L alanine to the standard WHO-ORS produces no further improvement in the outcome of the infants with acute diarrhea compared with those fed the standard WHO-ORS.

Cereal-based oral rehydration therapy. I. Clinical studies

Studies of "improved" oral rehydration solutions, in which glucose polymers (starch) derived from rice or other cereals were added to improve cotransport of sodium and to promote sodium and water absorption, have been reported. These solutions were administered to decrease diarrhea volume and duration, reduce vomiting, and replace volume loss in stools. In clinical trials of children and adults with high-output diarrhea, such as in cases of cholera, the use of cereal-based oral rehydration solutions (ORS) compared with glucose-based ORS produced significant (20% to 53%) reductions in stool volumes. In one study the duration of diarrhea was shortened by 30%. In noncholera diarrhea in children, cereal-based ORS was as effective as glucose-based ORS. Although the amino acid transport systems were intact in patients with cholera, the addition of glycine to glucose-based or rice-based ORS did not reduce stool volume or duration of diarrhea. The exception was alanine, which reduced stool output and ORS requirements. More research is needed to determine the optimal mix of starch, amino acids, oligopeptides, and proteins that would utilize the absorptive active transport systems maximally to reduce fluid losses and duration of diarrhea.

Rice-based oral electrolyte solutions for the management of infantile diarrhea

BACKGROUND

In infants the treatment of acute diarrhea with glucose-based solutions results in rehydration but does not reduce the severity of diarrhea. Oral rehydration with solutions based on rice powder may reduce stool output as well as restore fluid volume.

METHODS

We designed a prospective, randomized, double-blind study to evaluate the efficacy of two rice-based rehydration solutions and a conventional glucose-based solution. Solution A contained only rice-syrup solids, solution B contained rice-syrup solids and casein hydrolysate, and solution C, the glucose-based solution, served as control. The study subjects were 86 mildly to moderately dehydrated infant boys, 3 to 18 months old, who were admitted to a children's hospital with acute diarrhea. We measured fluid intake, fecal and urine output, and absorption and retention of fluid, sodium, and potassium at intervals for 48 hours in all 86 infants.

RESULTS

The mean (+/- SE) fecal output was significantly lower in the infants given solution A (group A infants) than in the infants given solution C (group C) (29 +/- 4 vs. 46 +/- 7 ml per kilogram of body weight, P less than 0.05) during the first six hours of therapy. The infants in group A also had greater fluid absorption (221 +/- 16 vs. 167 +/- 9 ml per kilogram, P less than 0.05) over the entire 48 hours of therapy and greater potassium absorption (1.6 +/- 0.2 vs. 0.6 +/- 0.1 mmol per kilogram, P less than 0.05) during the first six hours than the infants in group C. Solution B offered no advantages over solution A.

CONCLUSIONS

Solutions containing rice-syrup solids were effective in the rehydration of infants with acute diarrhea. They decreased stool output and promoted greater absorption and retention of fluid and electrolytes than did a glucose-based solution.

A comparison of rice-based oral rehydration solution and "early feeding" for the treatment of acute diarrhea in infants

To compare the use of rice-based oral rehydration solution (R-ORS), with the introduction of food immediately after rehydration ("early feeding"), using standard glucose-based oral rehydration solution (G-ORS) in the management of acute diarrhea, we conducted a four-cell randomized, controlled trial among 200 hospitalized Egyptian infants between 3 and 18 months of age. During the rehydration phase (first 4 hours), three groups were given G-ORS and a fourth group was given R-ORS. During the subsequent maintenance phase, the control group was given a soy-based, lactose-free formula (G-ORS + SF), a second group (G-ORS + RF) was given a rice-based formula, and a third group (G-ORS + rice) was given boiled rice. The fourth group (R-ORS + SF) continued to receive R-ORS for the first 24 hours of the maintenance period, followed by a soy-based lactose-free formula. During the first and second 24 hours of the maintenance period, infants in the three treatment groups had a lower mean stool output in comparison with the control group (p = 0.006 and 0.03, respectively). The mean total stool output in the R-ORS + SF group was significantly lower than in the control group (p = 0.02). There were no statistically significant differences among the four groups in the mean duration of diarrhea. We conclude that (1) infants who were given R-ORS had reduced total stool output (by 35%) compared with the control group and (2) feeding of boiled rice or a rice-based formula immediately after rehydration therapy was as efficacious as treatment with R-ORS alone for 24 hours, followed by feeding with a soy-based, lactose-free formula.

Glycine, glycyl-glycine and maltodextrin based oral rehydration solution. Assessment of efficacy and safety in comparison to standard ORS

We evaluated the efficacy and safety of an oral rehydration solution containing glycyl-glycine, glycine, and maltodextrin (GGG-ORS), in comparison to the glucose based ORS (standard ORS). The osmolality of the GGG-ORS (305 mOsm/l) and standard ORS (311 mOsm/l) was similar. Ninety-two children presenting with acute gastroenteritis and moderate dehydration, aged 3 months to 3 years, were randomly assigned to receive standard ORS or GGG-ORS. All the patients were successfully rehydrated orally. The two groups were comparable for baseline characteristics including the microbial etiology. Rotavirus (49%, 36%), ETEC (11%, 18%) or a combination of rotavirus and ETEC (15%, 9%) were the main stool pathogens isolated. There was no significant difference in the mean stool output or duration of diarrhoea between the two groups. Patients in the GGG-ORS group had higher urine output (p less than 0.01) and weight gain (p less than 0.05) in the initial 6 hours when feeding was withheld, but no such differences were observed beyond this period. Hypernatremia did not develop in any patient during the study. We conclude that glycine and glycyl-glycine supplemented oral rehydration solution does not have any therapeutic advantage in the treatment of acute gastroenteritis with moderate dehydration caused predominantly by rotavirus.

Overview of childhood acute diarrhoea in Europe: implications for oral rehydration therapy

Infant mortality from acute diarrhoea has sharply declined in the last few decades throughout Europe. However, acute diarrhoea is still a very common occurrence in European children, who experience, in their first 3 years of life, approximately 1 episode/year. The commonest agent responsible for infectious diarrhoeas appears to be rotavirus, followed by campylobacter. Although water loss may be high, the mean sodium loss is close to 40 mmol/l of stool in rotaviral diarrhoea, and to 60 mmol/l in diarrhoeas due to invasive pathogens such as campylobacter and salmonella. Larger fluid losses but a somewhat lower sodium loss accompanies non-cholera secretory diarrhoeas, which appear to be commoner in infants than in older children. This evidence indicates that an ORS for European children should have a sodium concentration lower than 90 mmol/l which was primarily intended for use in developing countries. Clearly, the glucose concentration is crucial, as it is now evident that concentrations higher than the recommended 110 mmol/l may lead, particularly in rotaviral enteritis, to worsening of diarrhoea and development of hypernatraemia. Finally, it appears that in Europe the use of commercially available ORS is strikingly low, so that infants and children are often given a variety of "clear fluids", generally inadequate to ensure proper rehydration or maintenance of hydration. Thus an effort should be made not only to devise the "ideal" solution, but also to effectively implement its use.

Optimising oral rehydration solution composition for the children of Europe: clinical trials

Clinical trials testing different oral rehydration solutions (ORS) are reviewed. The effects of individual components and their concentrations are analysed in order to establish margins of safety for the composition of the ideal ORS for children in Europe. Glucose is the solute of choice for ORS and concentrations of 70-140 mmol/l are adequate. Glucose may be replaced by sucrose or glucose polymers. "Low" sodium concentrations (35-60 mmol/l) are advised for rehydration and maintenance in acute non-cholera diarrhoea, for children of all ages, including neonates, and for any degree of dehydration except shock. Although intended for children who are not malnourished, the European ORS should have an adequate potassium concentration (20-30 mmol/l), namely the same concentration as found in WHO-ORS. Chloride concentration depends upon other constituents of ORS, namely sodium and potassium, but the range of 30-90 mmol/l is considered to be adequate. Base or base precursors are not required for correction of acidosis except in the severe cases that always need intravenous replacement. A relatively low osmolality seems advisable.

Optimising oral rehydration solution composition in model systems: studies in normal mammalian small intestine

Small intestinal perfusion studies have been carried out in animals to evaluate the role of the individual constituents of oral rehydration solution (ORS), in order to draw some conclusions relating to the optimal composition of ORS. Two commercially available ORS, Dioralyte and Rehidrat have also been compared to the World Health Organisation (WHO) standard solution. Maximum rate of water absorption occurred with the WHO solution and least with Rehidrat. The findings of the perfusion studies suggest that in the normal small intestine, optimal water absorption occurs from a solution containing 60 mmol/l of sodium and 80-120 mmol/l of glucose. The addition of bicarbonate and citrate at concentrations present in ORS does not appear to have a significant effect on water absorption. The addition of glycine and diglycine to the standard ORS reduced the net rate of absorption of sodium and water, probably because of the effect of increased osmoality.

Oral rehydration formula containing alanine and glucose for treatment of diarrhoea: a controlled trial

OBJECTIVE

To determine whether adding L-alanine to the glucose based oral rehydration solution recommended by the World Health Organisation would improve its efficacy in treating acute diarrhoea.

DESIGN

Randomised double blind controlled trial of oral rehydration solution containing L-alanine and glucose.

SETTING

Inpatient service of a hospital treating diarrhoea.

PATIENTS

97 Male patients aged 6-59 years admitted to the hospital with acute and severe dehydration due to diarrhoea associated with Vibrio cholerae or enterotoxigenic Escherichia coli. Forty nine received the standard glucose based oral rehydration solution (control group) and 48 this solution with alanine added (study group).

INTERVENTIONS

All of the patients received rapid intravenous acetate solution for the initial four hours after admission, which fully corrected the signs of dehydration. They were then admitted to the study and randomised. Immediately after the intravenous treatment oral rehydration treatment was started. All of the patients received oral tetracycline for 48 hours, starting 24 hours after start of the study. If signs of dehydration reappeared during oral treatment patients were given rapid intravenous acetate solution until they were fully corrected and then continued to take the assigned oral rehydration solution.

END POINT

Passage of the last watery stool.

MEASUREMENTS AND MAIN RESULTS

The median stool output/kg body weight during the initial 24 hours of oral rehydration treatment and until diarrhoea stopped was reduced in the study group compared with the control group from 309 ml to 196 ml and from 393 ml to 236 ml respectively. Intake of oral rehydration solution and intravenous acetate solution was reduced from 455 ml to 308 ml and from 616 ml to 425 ml respectively. Two patients in the study group compared with 18 patients in the control group required unscheduled rapid intravenous acetate solution to correct signs of dehydration during oral rehydration treatment.

CONCLUSION

Oral rehydration solution containing L-alanine was considerably better than standard oral rehydration solution at reducing the severity of symptoms and the need for fluid of male patients with diarrhoea associated with V cholerae and enterotoxigenic E coli.

Experimental models for the investigation of water and solute transport in man. Implications for oral rehydration solutions

For patients suffering from mild to moderate dehydration, oral rehydration therapy has proved a simple and efficacious treatment. There remains, however, a need to develop improved oral rehydration solutions (ORS), and suitable experimental models are required to develop and assess new formulations. The ideal model for such investigations would take into account rates of gastric emptying, influx and efflux of water and solutes in the intestine, and the consequent changes in body composition. As no such definitive model is currently available, a variety of techniques are used to examine parts of the process of intestinal absorption. Clinical studies which assess the recovery of dehydrated patients during therapy using different ORS will ultimately evaluate the efficacy of treatment. However, ethical considerations, the relative insensitivity of this technique and the exacting nature of such studies make this approach unsuitable for the development of specific ORS. Gastric emptying of solutions can be determined by a variety of techniques, among which the radioactive tracer method offers the advantage of having no direct effect on the emptying rate, giving almost continuous measurement and allowing the use of relatively small volumes of fluids. Perfusion techniques allow measurement of the net flux of water and solute in predetermined sections of the intact human intestine. Measurement of the rate of accumulation in the circulation of orally ingested tracer molecules for water and solutes can estimate unidirectional flux. This method allows for the rates of gastric emptying and intestinal absorption of the test substance, but the rate of efflux of the tracer from the vascular space must be known to calculate net uptake. Each of these models has limitations, and care must be taken in interpreting the results in a clinical context. However, their use in the development of improved formulations is well established.