Esophageal hypersensitivity/Functional heartburn are common among non-erosive reflux disease (NERD) patients who do not response to proton pump inhibitors. Whether tricyclic antidepressant improves NERD patient's symptoms remains unknown

Aim of this randomized controlled trial study is to determine the efficacy of imipramine, which could increase esophageal pain thresholds in healthy volunteers, in comparison with placebo for treatment patients with esophageal hypersensitivity or functional heartburn evaluated by improvement of specific-symptom score and quality of life

Inclusion Criteria:

• patient with typical reflux symptoms (heartburn and/or regurgitation) more than 3 times per week in at least last 3 months
• Age more than 18 years
• Upper GI endoscopy showed no esophageal mucosal breaks
• MII-pH monitoring was not showed abnormal both acid and non-acid reflux
• symptoms was not improved after received standard dose proton pump inhibitor for at least 1 month

Exclusion Criteria:

• history of thoracic, esophagus, or stomach surgery
• severe esophageal motility disorder eg. Achalasia, scleroderma, autonomic/peripheral neuropathy/myopathy
• patient who was indicated to receive proton pump inhibitor
• pregnant women
• patient who was allergy to imipramine
• patient who received tricyclic antidepressant or SSRI with in 3 month of enrollment