Ranitidine--rifampicin interaction.

Newly diagnosed patients of pulmonary tuberculosis (n = 112) were put on a rifampicin-containing drug regimen. Fifty six patients were also given a placebo tablet twice daily while the other fifty-six were given ranitidine 150 mg twice daily. Gastric pH, gastric emptying time, serum rifampicin levels, urinary total and unchanged rifampicin, serum bilirubin and ALT levels were measured serially. Clinical record of adverse symptoms was maintained. Ranitidine increased the basal as well as post-drug gastric pH without altering the gastric emptying time. Concomitant administration of ranitidine and rifampicin did not alter the absorption, metabolism or excretion of the latter but reduced the frequency of gastrointestinal symptoms.