The Effect of Rikkunshito on Gastric Accommodation and Nutrient Volume Tolerance in Functional Dyspepsia

Inclusion Criteria: 1. Patients with FD-postprandial distress syndrome subtype diagnosis as per Rome IV 2. Patients must provide witnessed written informed consent prior to any study procedures being performed 3. Patients aged between 18 and 75 years inclusive 4. Male or female patients. Women of child-bearing potential agree to apply during the entire duration of the trial a highly effective method of birth control, which is defined as those which result in a low failure rate (i.e., less than 1% per year) when used constantly and correctly such as implants, injectables, combined oral contraceptive method, or some intrauterine devices (IUDs), sexual abstinence, or vasectomized partner. Women of non-childbearing potential may be included if surgically sterile (tubal ligation or hysterectomy) or postmenopausal with at least 2 year without spontaneous menses. 5. Patients who are capable to understand the study and the questionnaires, and to comply with the study requirements Exclusion Criteria: 1. Patients with any condition which, in the opinion of the investigator, makes the patient unsuitable for entry into the study 2. Patients with an active major psychiatric condition (depression, anxiety disorder, alcohol or substance abuse). However, patients who are taking a stable dose of a single antidepressant (with the exception of amitryptiline and mirtazapine which are forbidden) during the last 3 months are eligible. 3. Females who are pregnant or lactating. Females who refuse to take appropriate contraception at the time of informed consent. 4. Men who want to donate sperm during the study and during the 4 weeks after stopping Rikkunshito. 5. Patients who received treatment for Helicobacter Pylori (HP) eradication during the last 3 months. Patients who are HP positive may enter the study provided that their endoscopy is negative. If HP status is unknown, determination of HP status will be done during run-in. 6. Patients suffering from diabetes type 1 or type 2. 7. Patients taking drugs affecting the gut secretion, mucosal integrity (non-steroidal anti-inflammatory drugs (NSAIDs), with an exception for aspirin at cardioprotective dose of max 125 mg daily), motility, and/or sensitivity. Patients taking proton pump inhibitors (PPIs) are eligible provided that FD is predominant and heartburn limited to maximum two episodes of mild intensity per week. 8. Patients with coronary heart disease, arrhythmias or taking concomitant drugs capable to prolong the QT. 9. Patients taking concomitant drugs able to induce drug-drug interaction (P450), Concomitant drugs interacting substantially with the different fractions of cytochromes (CYP3A4 and others) and with strong protein binding (Albumine, i-globulins, acid glycoproteins) are excluded. 10. Patients with a significant renal \[serum creatinine \>2 x upper limit of normal (ULN)\], hepatic \[alanine transaminase (ALT), aspartate transaminase (AST), gamma glutamyltransferase (GGT), bilirubin \>2 x ULN\], cardiovascular, pulmonary, endocrine, metabolic or haematological condition. 11. Patients with known hypersensitivity to the Ginseng or Ginger. 12. Patients with confirmed gastro-intestinal disease. 13. Patients with former digestive surgery affecting upper gut motility. 14. Patients affected by concomitant extra-digestive disease responsible for digestive symptoms. 15. Patients presenting with predominant symptoms of irritable bowel syndrome (IBS). 16. Patients presenting symptoms of epigastric pain syndrome (EPS) several times a week, not related to meals, according to Rome III questionnaire (score 5 or higher on question 10, in combination with clinical judgement). 17. Patients presenting daily symptoms of nausea syndrome, not related to meals, on Rome III questionnaire (score 6 on question 6 or score 5 or higher on question 9). 18. Patients presenting vomiting more than one day a month. 19. Patients presenting daily symptoms of Excessive belching according to Rome III questionnaire (score 6 on question 19, in combination with clinical judgement). 20. Patients presenting predominant gastro-esophageal reflux disease (GERD) (3 "yes" by GERD questionnaire, in combination with clinical judgement). 21. Patients not willing to take ultraviolet protective measures or patients at increased risk for phototoxicity (use of drugs like tetracyclins, amiodarone, sulphonamides, quinolones).