Comparison of 200 mg Cimetidine with Multiple Doses of Antacid on Extent and Duration of Rise in Gastric pH in Volunteers

Abstract

The effects on gastric pH of a singleadministration of 200 mg cimetidine (Tagamet HB) werecompared to multiple doses of a liquid antacid (Mylanta)using a pH microelectrode. Gastric pH was monitored for 8 hr in 20 normal fasting volunteers in acrossover design to compare Tagamet HB (two 100-mgtablets administered as a single dose) with MylantaSuspension, an initial 17.5-ml dose of antacid withadditional doses given when gastric pH fell below 3.5.Both treatments increased the pH above 3.5 during thefirst hour following treatment, with Mylanta being moreeffective than Tagamet HB. Interestingly, to sustain the reduction in acidity during this 1-hrinterval, a mean of 2.45 doses of antacid wereadministered. Although multiple doses of Mylanta keptthe pH above 3.5 (for at least 25% of the time) for thefirst 4 hr, the single administration of 200 mg ofTagamet HB maintained gastric pH above 3.5 (greater than25% of time) for the full 8 hr of the study. Compared toMylanta, the percent of time gastric pH was >3.5 was significantly higher with TagametHB during the 3rd to 8th hour after dosing. This studydemonstrates that 200 mg of cimetidine administered asTagamet HB is significantly more effective and has a much longer duration of action in raisinggastric pH >3.5 than six doses of Mylanta.