AIM:To study the effect of rabeprazole (RAB) on nocturnalacid breakthrough (NAB) and nocturnal alkaline amplitude(NAKA) and to compare it with omeprazole (OME) andpantoprazole (PAN).METHODS:By an open comparative study,forty patientswith active peptic ulcer were randomly assigned to receiveone of the three PPIs (proton pump inhibitor) with a singleoral dose.They were divided into RAB group (10 mg),OMEgroup(20 mg) and PAN group (40 mg).Twenty healthyvolunteers were enrolled to the control group (without takingany drug).Intragastric pH monitoring was then performed1 hour before and 24 hours after the dose was given.RESULTS:No clinically undesirable signs and symptomspossibly attributed to the administration of RAB or OME andPAN were recognizable throughout the study period.Allsubjects completed the study according to the protocol.Alldata were processed by a computer using the Student ttestor t’ test followed by an analysis of covariance.P<0.05 wasconsidered to have statistical significance.The intragastric pHof NAB was significantly higher in RAB group (1.84±0.55) thanin either OME group (1.15±0.31) or PAN group (1.10±0.30)(both P<0.01).RAB produced a longer sustaining time(4.65±1.22 h) on NAKA than OME (3.22±1.89 h) (P<0.05),PAN (3.15±1.92 h) (P<0.05),and the sustaining time ofNAKA in RAB group was longer than that in the healthycontrol group (P<0.01) too.In addition,RAB produced amuch higher pH on NAKA (6.41±0.45) in comparison withPAN (6.01±0.92) (P<0.05).CONCLUSION:A single oral dose of 10 mg RAB mayincrease the pH of NAB and shorten the sustaining time ofNAB,and it may increase the pH of NAKA as well as prolongthe sustaining time of NAKA. AIM: To study the effect of rabeprazole (RAB) on nocturnalacid breakthrough (NAB) and nocturnal alkaline amplitude (NAKA) and to compare it with omeprazole (OME) andpantoprazole (PAN) .METHODS: By an open comparative study, forty patients with active peptic ulcer were randomly assigned to receive one of the three PPIs (proton pump inhibitor) with a single oral dose. They were divided into RAB group (10 mg), OMEgroup (20 mg) and PAN group (40 mg). Twenty healthy volunteers were enrolled to the control group (without taking the drug) .Intragastric pH monitoring was then performed 1 hour before and 24 hours after the dose dose given. RESULTS: No clinically unnecessary signs and symptomspossibly attributable to the administration of RAB or OME and PAN identified by the study period. Airllsjects completed the study according to the protocol. Alldata were processed by a computer using the Student t testor t ’test followed by an analysis of covariance. P <0.05 wasconsidered to have statistical significan (1.84 ± 0.55) thanin either OME group (1.15 ± 0.31) or PAN group (1.10 ± 0.30) (both P <0.01) .RAB produced a longer sustaining time (4.65 ± 1.22 h) on NAKA than OME (3.22 ± 1.89 h) (P <0.05), PAN (3.15 ± 1.92 h) (P <0.05), and the sustaining time of NAKA in RAB group was longer than that in the healthy control group <0.01). In addition, RAB produced amuch higher pH on NAKA (6.41 ± 0.45) in comparison with PAN (6.01 ± 0.92) (P <0.05) .CONCLUSION: A single oral dose of 10 mg RAB mayincrease the pH of NAB and shorten the sustaining time of NAB, and it may increase the pH of NAKA as well as prolong the sustaining time of NAKA.