Background: Considering the high secretion of gastric acid in peptic ulcer, its known complications and failure to previous therapeutic regimens, and also regarding history of prescribing peppermint essential oil in the treatment of gastric disorders and lack of information about interactions between peppermint essential oil and secretion of acid by parietal cells, this study was performed.

Materials and Methods: This experimental study was conducted on 60 male rats, species Sprague Dawley. Rats were divided in 6 equal groups. Each group received normal saline (0.9%) and menthol with doses of 0.9, 2.7, 9, 27 and 90 mg/kg by plastic cannula, respectively. Gastric secretion was extracted from pylorus. Gastric acidity was evaluated using titration by NaOH. Data analysis was performed by t-test, paired t-test, one way ANOVA and tukey's test.

Results: Rate of gastric acid secretion was constant in rats received normal saline, while it increased in rats received peppermint essential oil. Peppermint essential oil with dose of 9 mg/kg decreased acid secretion from 100 to 61.1±3.8 percent at the beginning of prescribing. Increasing dose aggravated the efficacy of peppermint essential oil on inhibiting acid secretion. The maximum of effect was seen in dose of 27 mg/kg. The effect of peppermint essential oil was reversible and after washing stomach with normal saline, this inhibitory effect was disappeared.

Conclusion: It seems that peppermint essential oil has dose-dependent and reversible inhibitory effect on gastric acid secretion. So, it is recommended to patients with gastritis to decrease prescribing anti-secretory drugs.