Current treatment for gastroesophageal reflux disease(GERD)confirms an unmet need in patients, based on slow onset of action and an inability to provide 24-hour gastric acid suppression. Clinical data on lavoltidine demonstrates a rapid onset of action, high potency, and prolonged duration of effect after single dose. Since tolerance to the class of compounds to which lavoltidine belongs may be dose dependent, the current study is designed to determine if 40mg lavoltdine given for 7days develops tolerance.