In a placebo-controlled, double-blind, multiplecrossover study, the initial and chronic acid-inhibitoryeffect of lansoprazole 30 mg, orally administered halfan hour before breakfast or immediately after breakfast, and of omeprazole 20 mg,administered postprandially, respectively, wasinvestigated in 16 healthy volunteers, using ambulant24-hr intragastric pH monitoring. On the first day ofmedication, only preprandially administered lansoprazolereduced acid secretion significantly (median 24-hr pH3.0; P < 0.05).="" on="" day="" 15,="" the="" median="" 24-hrintragastric="" ph="" of="" lansoprazole="" preprandial="" (ph="" 4.1),lansoprazole="" postprandial="" (ph="" 4.3),="" and="" omeprazolepostprandial="" (ph="" 3.3),="" respectively,="" differedsignificantly="" (p="">< 0.05)="" from="" placebo="" (ph="" 1.2).="" it="" isconcluded="" that="" the="" interaction="" between="" food="" intake="" andlansoprazole="" administration="" only="" is="" important="" at="" the="" startof="" oral="" therapy.="" lansoprazole="" taken="" before="" breakfast="" iseffective="" even="" on="" the="" initial="" day="">