Some medications require an acid environment for its absorption,
like ketoconazole, ampicillin or iron, and may
have a decline of their bioavailability from 5 to 10%, as a
result of hypochlorhydria secondary to atrophic gastritis or
treatment with H2 antagonists and proton-bomb inhibitors.
In the elderly, the hepatic metabolism of the first step is diminished, and oral medication bioavailability which
goes through this process is greater.