Patients who require gastric endoscopy will receive an intragastric single dose of NPO-11 20 mL. The superiority of NPO-11 to placebo as a premedication for endoscopy will be verified in a randomized, double-blind, parallel-assignment design based on the percentage of patients having no gastric peristalsis at both 2 minutes post-dose and the end of endoscopy (primary outcome measure).

The safety of NPO-11 will be evaluated based on adverse events and adverse drug reactions (ADRs) observed between administration and seven days after administration in comparison with the placebo group.

Inclusion Criteria:

Inpatients or outpatients of either sex who visit medical institutions for treatment or follow-up of confirmed or suspected upper gastrointestinal disease (symptoms) and meet the criteria (1) and (2) below will be enrolled in the study. Patients have to provide written informed consent for voluntary participation in the study.

1. Patients who need gastric endoscopy (except for endoscopy with a scope of <9 mm in diameter, emergency endoscopy and endoscopy for comprehensive medical examination)
2. Patients who are older than 20 years at the time of consent

Exclusion Criteria:

Patients who meet any of the following criteria will be excluded from the study. The criteria (2) to (5) will be confirmed during endoscopy. Patients who meet any of these criteria will be withdrawn from the study at the time of confirmation.

1. Patients with a history of surgery to the upper gastrointestinal tract
2. Patients with severe gastric stenosis or deformation which makes observation of gastric peristalsis difficult
3. Patients with upper gastrointestinal bleeding which requires hemostasis
4. Patients with reflux esophagitis (Los Angeles classification: B, C or D)
5. Patients with gastric or duodenal ulcers in active stage
6. Patients on cancer treatment (chemotherapy or radiotherapy)
7. Patients with impaired cardiac function (NYHA functional classification: III or IV)
8. Patients with a history of shock or hypersensitivity to l-menthol or peppermint oil (mint oil)
9. Patients with a history of shock or hypersensitivity to lidocaine hydrochloride
10. Pregnant or lactating women, women of childbearing potential, or women who plan to become pregnant during the study
11. Patients who have been exposed to NPO-11
12. Patients who have received other investigational drugs within four months before consent or who are participating in other clinical studies
13. Patients otherwise ineligible for participation in the study in the investigator's or subinvestigator's opinion