Intra- and inter-subject variability in gastric pH following a low-fat, low-calorie meal

Food can alter drug bioavailability through gastric pH changes. Time spent at gastric pH ranges is reported here, including variability data following ingestion of a light, mixed, 260 kcal meal. pH data was obtained for 20 healthy subjects undergoing SmartPill™ wireless motility capsule investigations on three separate visits. Gastric phase pH was sorted into pH < 2, 2-3, 3-4, 4-5 and > 5. All visits and all subjects were pooled to determine median time (25-75th percentiles) in minutes. Gastric emptying time was 176 (137-205) min with the majority of time, 111 (67 - 163), spent at pH < 2. Times spent at pH 2-3 and 3-4 were similar: 17 (5.7 - 35.6) and 18 (7.2-29.3). Time spent at pH 4-5 was 9 (1.3-20.6) and at pH > 5 was 0.7 (0-4.4). Intra-subject variability as determined by robust coefficient of variation (RCV)% was 30 % for pH < 2, 57 % for pH 2-3, 71 % for pH 3-4, 106 % for pH 4-5 and 144 % for pH > 5. Inter-subject variability RCV% was 49 % for pH < 2, 89 % for pH 2-3, 54 % for pH 3-4, 97 % for pH 4-5 and 148 % for pH > 5. Inter-subject variability can be up to approximately twofold higher than intra-subject variability at the lower pH ranges.