Efficacy and Mechanistic Evaluation of Hewei Anchang Formula for Overlapping Gastrointestinal Symptoms in Patients With Coexisting Functional Dyspepsia and Diarrhea-Predominant Irritable Bowel Syndrome

Functional gastrointestinal disorders (FGIDs) comprise a group of gastrointestinal conditions characterized predominantly by gastrointestinal symptom complexes in the absence of identifiable structural abnormalities or clearly defined pathophysiological mechanisms. Individual FGIDs are diagnosed primarily on the basis of symptom profiles and commonly present with manifestations such as reflux, heartburn, dyspepsia, abdominal pain, bloating, diarrhea, and constipation. The boundaries between different FGIDs are not distinct, and symptom overlap is common. Such overlap not only increases disease complexity and substantially complicates clinical diagnosis and management, but also increases healthcare utilization and imposes a considerable adverse impact on patients' quality of life. According to the Rome IV criteria, each patient with an FGID receives, on average, 1.5 FGID diagnoses, and approximately 36% of patients have FGIDs involving two or more gastrointestinal regions, representing a typical pattern of symptom overlap.

Among the various overlapping phenotypes of FGIDs, the coexistence of functional dyspepsia (FD) and diarrhea-predominant irritable bowel syndrome (IBS-D) is one of the most common. These patients experience both typical upper gastrointestinal symptoms of FD, including postprandial fullness, early satiety, and epigastric pain, and core lower gastrointestinal manifestations of IBS-D, such as abdominal pain, diarrhea, and altered stool form, making this overlap phenotype a major challenge in gastroenterological practice. Compared with patients with FD or IBS-D alone, those with coexisting FD and IBS-D tend to experience more persistent, frequent, and severe symptoms. These symptoms can substantially affect eating habits, daily routines, social activities, and other aspects of everyday life, thereby markedly impairing quality of life. Repeated healthcare-seeking behavior also increases both individual medical expenditures and the consumption of healthcare resources, making this condition an important clinical and public health concern requiring effective intervention.

The clinical management of overlapping gastrointestinal symptoms in FGIDs remains challenging. Conventional pharmacological treatments often act on limited therapeutic targets and may therefore provide suboptimal efficacy in patients with overlapping symptom profiles, while also contributing to a substantial socioeconomic burden. Commonly used medications, including prokinetic agents, proton pump inhibitors, antidiarrheal agents, and anticholinergic antispasmodics, generally target symptoms arising from a single gastrointestinal region. Consequently, treatment outcomes may be unsatisfactory when upper and lower gastrointestinal symptoms coexist. Although combination pharmacotherapy may address multiple symptoms, it may also increase the risk of adverse drug reactions, and some patients discontinue treatment because of poor tolerability or adverse effects, resulting in limited overall clinical benefit. In addition, the pathophysiology of coexisting FD and IBS-D is complex and has been associated with multiple interacting mechanisms, including gastrointestinal dysmotility, gut microbial dysbiosis, and dysregulation of the neuroendocrine-immune network. Thus, single-target pharmacotherapy may be poorly suited to the multifactorial pathophysiological features of this overlap phenotype, which may partly explain its limited therapeutic effectiveness.

Patients with FD and IBS-D frequently experience psychological disturbances, including anxiety and depression. From the perspective of traditional Chinese medicine (TCM), liver qi stagnation is considered a key underlying pathogenesis, while spleen-stomach deficiency and liver stagnation with spleen deficiency are among the most common syndrome patterns in patients with overlapping FD and IBS-D. Accordingly, strengthening the spleen and regulating qi, as well as soothing the liver and strengthening the spleen, are regarded as core therapeutic principles. Owing to its holistic regulatory effects and individualized treatment based on syndrome differentiation, TCM may be particularly well suited to the multifactorial pathophysiology of overlapping FGIDs. Guided by the TCM principle of "treating different diseases with the same therapeutic approach," TCM interventions may target the shared pathogenesis of liver stagnation with spleen deficiency through multicomponent, multitarget, and multipathway mechanisms, thereby exerting integrated effects on gastrointestinal function, emotional well-being, and internal homeostasis. This therapeutic model may offer advantages over conventional single-target symptomatic treatment.

Chaihu Shugan San has the traditional actions of regulating qi, relieving stagnation, harmonizing the stomach, and redirecting rebellious qi downward, and has been strongly recommended in several expert consensuses and clinical guidelines for the treatment of FD with liver-stomach disharmony syndrome. Based on more than four decades of clinical experience, Professor Xudong Tang of Xiyuan Hospital, China Academy of Chinese Medical Sciences, proposed the theory of "regulating the middle and restoring balance." Under the guidance of this theory, Chang'an I Formula was developed according to the core pathogenesis of IBS-D. Hewei Anchang Formula is an optimized herbal formula derived from Chang'an I Formula and modified Chaihu Shugan San, with modifications tailored to the pathophysiological characteristics of liver-stomach disharmony syndrome in FD and liver stagnation with spleen deficiency syndrome in IBS-D. The formula has demonstrated promising clinical effects. Based on the theory of "regulating the middle and restoring balance," Hewei Anchang Formula is designed to address the core pathogenesis of overlapping gastrointestinal symptoms in FD and IBS-D, with therapeutic actions aimed at strengthening the spleen, soothing the liver, regulating qi, and alleviating diarrhea. Its composition is therefore closely aligned with the principles of TCM syndrome differentiation and provides a suitable intervention for investigating TCM-based treatment of this overlap phenotype.

This study is designed as a multicenter, randomized, double-blind, placebo-controlled clinical trial and will enroll 120 patients with overlapping gastrointestinal symptoms of FD with liver-stomach disharmony syndrome and IBS-D with liver stagnation-spleen deficiency syndrome. The study aims to evaluate the clinical efficacy and potential therapeutic advantages of Hewei Anchang Formula in the treatment of coexisting FD and IBS-D. Metagenomic and metabolomic approaches will also be used to investigate its potential mechanisms of action, with particular emphasis on the gut microbial ecosystem and the neuroendocrine-immune network. The findings are expected to provide a practical TCM-based therapeutic strategy for improving the overall management of overlapping gastrointestinal symptoms in FGIDs and reducing the associated medical and socioeconomic burden.