In order to establish the therapeutic plasma concentration of famotidine, the 24-h intragastric pH response to low-dose intravenous (i.v.) continuous infusion of 40 (group A) or 20 mg/day (group B), administered over more than two days, was studied in 10 adult patients with active gastric ulcers (GU). In group A, the mean age was 64.8 years and in group B, 54.2 years. On the second day, 4 blood samples were collected for famotidine assay and 24 h intragastric pH monitoring was performed.
Results: the mean 24 h pH did not differ significantly (P less than 0.01) between group A at 6.9 and group B at 7.2. In group A, the percentage of time with pH above 6.0 and above 7.0 were 94.8 and 59.0, respectively, and the mean famotidine dose and plasma concentration were 0.81 mg/kg/day and 140.89 ng/ml. In group B, the percentage of time with pH above 6.0 and 7.0 were 97.6 and 65.4, and the mean dose and famotidine concentration were 0.34 mg/kg/day and 45.42 ng/ml. In conclusion, in fasting patients with active gastric body ulcers, continuous infusions of low-dose famotidine maintain both the therapeutic plasmatic concentration and the intragastric pH to near anacidity level.