Combination therapy with ranitidine and pirenzepine for control of intragastric pH in the critically ill.

In a prospective study of pH control for stress ulcer prophylaxis, intermittent iv infusion of the anticholinergic drug pirenzepine maintained the intragastric pH above 4 in only one of 17 ICU patients, while similar administration of the H2-receptor antagonist ranitidine was successful in seven of 32 patients. This difference was not statistically significant. Of 15 patients in whom a maximum dose of 600 mg/day of ranitidine or 90 mg/day of pirenzepine failed to maintain pH, combination therapy was successful in 11, a significant (p less than .01) improvement. We conclude that neither ranitidine nor pirenzepine provides adequate control of pH for stress ulcer prophylaxis when used alone. If used together they are the most effective combination so far described for parenteral control of gastric pH in the critically ill. Regular monitoring of gastric pH is nevertheless essential to allow detection of therapeutic failures.