To promote symptom relief from acid-related diseases, a medicine with a rapid-onset effect is ideal. The aim of this study was to investigate the early inhibitory effect on gastric acid secretion after a single oral administration of vonoprazan, which represents a new class of proton pump inhibitors, and to compare this effect with those of lansoprazole and famotidine. Ten Helicobacter pylori ( HP )-negative male subjects participated in this randomized, three-way crossover study. A single oral administration of vonoprazan (20 mg), lansoprazole (30 mg) or famotidine (20 mg) was performed, and the intragastric pH was continuously monitored for 6 h. Each drug was administered at least seven days apart. The average intragastric pH during the 6-h period after the administration of famotidine was higher than that after the administration of lansoprazole (median: 4.45 vs 2.65; p = 0.0284). A similar result was observed for vonoprazan and lansoprazole (median: 4.30 vs 2.65; p = 0.0322). In conclusions, oral administration of vonoprazan and famotidine in HP -negative healthy male subjects caused the intragastric pH to rise more quickly than did lansoprazole. (Trial Registration: UMIN000020989)