Sponsors of drug trials should determine what effect the use of acid-reducing agents (ARA), such as antacids, proton pump inhibitors and histamine blockers, could have on the solubility of an orally administered drug, according to a new FDA draft guidance released Monday.

Because ARAs are widely available over the counter, the FDA says, sponsors need to know if their use could decrease the efficacy or increase the risk of adverse events of an investigational drug. The guidance offers recommendations for determining when drug interaction studies are indicated, the design of such trials, how to interpret study results and how to communicate them in product labeling.

Standalone studies using healthy subjects could be conducted, and crossover trial designs are preferred, the guidance says. Results of studies using one ARA can be extrapolated to other ARAs of the same type.

Comments on the draft guidance are due Feb. 28.

Read the guidance here: https://bit.ly/3gurf2N.