This observational study is a large-scale, prospective, and multi-institutional observational study.

Patients from 19 to 75 years of age, will take a self-assessment (PRO) during the study period before and after administration of Pexuclue tablet.

Data will be collected based on patient's medical records from daily visit. Enrolled subjects will take a Patient Reported Outcome (PRO) survey including Quality of life evaluation (GERD-HRQL) and self-awareness symptom (RDQ).

The survey will be done twice (before and after the administration of Fexuclue tablet) electronically through an application (e-PRO).

Inclusion Criteria:

1. Adult aged 19 years to 75 years (on registration date)
2. Patient scheduled to administer Fexuclue tablet based on the medical judgment of investigator.
3. Patient who has not taken a treatment for gastroesophageal reflux disease within two weeks from baseline visit.
4. Patient who agreed to participate in this observation study and signed Informed Consent Form

Exclusion Criteria:

1. A person who falls under the prohibition of administration according to the permission for Fexuclue Tablet

   • Patients with hypersensitivity to the components of Fexuclue tablet or Fexuclue tablet and a history thereof
   • Patients undergoing Atazanavir, Nelfinavir or Lilpivirin-containing preparations
   • Pregnant and lactating women
   • Patients with genetic problems such as galactose intolerance, Lapp lactase deficiency, or glucose-galactose malabortion

2. A person who has taken a treatment for gastroesophageal reflux disease within two weeks from baseline visit.

3. In addition to the above, a person who has determined that the researcher (the doctor in charge) is not suitable for participation in this observation study

Referring to the minimum number of subjects required and the number of patients with gastroesophageal reflux disease in Korea, We expected to recruit about 16,000 people which is 0.2 %.

However, since this study is conducted under daily medical care, we expected 10% to be dropout rate.

Therefore the total study population is about 18,000

Undecided at this point