USA – From FDA: How to conduct DDI studies with acid-reducing drugs

A new draft guidance from the US Food and Drug Administration (FDA) addresses how to conduct drug-drug interaction studies with acid-reducing medicines that can make the gastric environment more alkaline.

Medicines such as proton pump inhibitors and histamine H2 receptor antagonists, dubbed acid-reducing agents or ARAs, are in wide use and many are available without a prescription. “ARAs can affect the solubility and dissolution characteristics of orally administered drug products by elevating gastric pH,” noted FDA’s Office of Clinical Pharmacology (OCP) in announcing the availability of the draft guidance for industry.

The FDA announcement noted that “concomitant administration of a drug with an ARA could alter the bioavailability of the drug, potentially resulting in a loss of efficacy for weak-base drugs or increased adverse events for weak-acid drugs.” The new document offers proposed guidance for assessing how susceptible an investigational drug is to gastric pH-mediated drug-drug interactions (DDIs) that may be clinically significant…