Time to maximum effect of lansoprazole on gastric pH in normal male volunteers

The time to maximum inhibition of gastric acidity resulting from repeated oral dosing with lansoprazole 30 mg daily for 7 days was studied in nine healthy male volunteers.

Twenty-four hour intragastric pH monitoring was performed before treatment and on days 1, 3, 5 and 7 of dosing with lansoprazole. Blood samples were taken for the estimation of plasma lansoprazole concentrations.

Lansoprazole 30 mg increased mean 24-h intragastric pH to 3.57 on day 1 compared with baseline mean pH of 2.11 (P < 0.05). The mean intragastric pH during the morning period (08.00-13.00 h) was significantly higher on days 3, 5 and 7 than on day 1, but no consistent differences between day 1, 3, 5 and 7 were noted for subsequent periods (13.00-18.00, 18.00-21.00 and 23.00-07.00 h). There were no differences in mean pH between days 3, 5 and 7. Intragastric pH was maintained above pH 3 for 54.7, 60.1, 61.9 and 67.4% of the time on days 1, 3, 5 and 7, respectively. Lansoprazole pharmacokinetic parameters did not change with daily dosing. The area under the lansoprazole plasma concentration-time curve correlated with the intragastric pH (P < 0.005).

Lansoprazole 30 mg raised intragastric pH significantly from baseline on day 1 to a maximum effect as early as 6 h after the first dose. The degree and duration of acid suppression confirm the usefulness of lansoprazole for the treatment of acid-related disorders.