Histamine2-receptor antagonists: Rapid development of tachyphylaxis with repeat dosing

Figure 1 Famotidine vs omeprazole for 14-d gastric acid control. Mean percentage of time gastric pH > 4 across 14 d of dosing in subjects with frequent heartburn[14] Famotidine (Fam) 10 mg or 20 mg was dosed twice a day. Omeprazole (Ome Mg 20) was dosed once a day (omeprazole-magnesium 20.6 mg). Gastric pH was assessed for 24-h on day 0 (baseline) and dosing days 1, 3, 7 and 14. Both famotidine doses showed a rapid decline in gastric acid control by dosing day 3, followed by a more gradual decline across 14-d of dosing. Omeprazole showed similar gastric acid control to famotidine 20 mg on dosing day 1, with an increase in gastric acid control over the first several days, followed by a sustained effect across 14-d of dosing (reprinted with permission[14]).