Food But Not a Chemically Defined Diet Interferes with Maintenance of Intragastric pH at a Predefined Level Using Continuous pH-Stat-Adjusted Intravenous Infusion of Ranitidine in Healthy Volunteers

Eight healthy volunteers were used to determinethe influence of a normal diet (food) versus anisocaloric chemically defined diet (CDD) on the dose ofranitidine infused continuously over 12 hr, required to maintain the intragastric pH ≥ 5 orabove. The dose of ranitidine used was adjusted by thepH-stat instrument, Gastrojet, and a target pH of 5.0was selected. The average ranitidine dose was 43.5 mg for food, 28.3 mg for CDD, and 25.7 mg forfasting. Despite the higher dose of ranitidine used withfood, the control of pH was lower than the desired andpreset value of pH ≥ 5: the average mean pH was 3.99 for food, 5.11 for CDD, and 5.75 forfasting. The percentage of time of pH ≥ 5 was 32.0%for food, 73.7% for CDD, and 80.1% for fasting. Thus,when persons are fed a normal diet there is a need for higher doses of ranitidine to maintain thegastric pH ≥ 5.0. Even with frequent monitoring ofintragastric pH with the Gastrojet, there is muchgreater variability in pH control with food than withCDD or fasting, and the preset and desired pH levelwas not achieved. This difficulty in achieving desiredend points of pH control when switching from a fastingto a fed state needs to be considered when intravenous ranitidine is used to obtain strict control ofintragastric pH.