Acute diarrhea, although tends to be a self-limiting disease in otherwise healthy people, continues to cause millions of deaths every year, particularly in infants and the elderly. Therefore it represents a very frequent medical problem with a significant societal impact such as health-care utilization and lost working days by caregivers. Dehydration, the most frequent and severe complication occurs in the first 48 hours from the onset of the disease. For this reason, the WHO considers this time frame the more critical period where we should mostly act. Oral rehydration solution is the most important component of treatment to avoid dehydration, but despite its proven effectiveness it is still rarely used because of low compliance mainly due to the subjective perception of poor effectiveness, as it does not reduce stools frequency, nor loss of intestinal liquids, neither the length of diarrhea. Racecadotril represents, so far, the unique drug acting on one of the main pathophysiological mechanisms underlying acute diarrhea. In this book some experts discussed the main international diarrheal guidelines in children and adults even analyzing the health costs of the disease. Other authors have thoroughly addressed the etiopathological mechanisms underlying acute diarrhea and some others have fully analyzed the clinical studies on Racecadotril present in the literature both in children and adults. In addition, the world's leading experts on Racecadotril have thoroughly clarified the drug's pharmacological mechanisms and have wonderfully summarized its safety profile. Finally we analyzed the cost-effectiveness of the drug based on the studies published so far, which confirm that Racecadotril can be a cost-saving drug in treating acute diarrhea because it can facilitate the home-management of the disease. All things considered, we can say that Racecadotril is an effective and safe anti-diarrheal drug that can reduce the associated health care costs by increasing the likelihood of resolving the disease in outpatient setting.