Effect of antacids on absorption of clorazepate

The effect of a magnesia and alumina antacid suspension on the absorption of clorazepate dipotassium was studied in 15 normal healthy adult subjects who ingested a 15-mg dose of clorazepate alone or with single or multiple doses of antacid. The results of this three-period randomized complete crossover study showed a trend of initially slower absorption and lower peak nordiazepam plasma levels when administered with the antacid suspension. However, there were no significant differences among treatments in the extent of absorption as measured by the area under the plasma level-time curves. Clorazepate plasma levels were of relatively short duration and similar for all treatments. The urinary excretion pattern was likewise comparable with conjugated oxazepam, the major species measured. Plasma elimination half-lives of nordiazepam and clorazepate were not affected by the antacid treatments.