Predictive factors for the effect of acid-reducing agents on drug exposure

Objectives: Acid-reducing agents (ARAs) may affect drug exposure for orally-administered drugs exhibiting pH-dependent solubility. The aim of this research was to investigate factors predicting the effect of ARAs on drug exposure. Dose (mg)/250 mL/solubility at neutral pH and ratio of solubility at acidic pH to that at neutral pH were investigated as potential factors. Materials and methods: Drug-drug interaction (DDI) study results with ARAs were selected based on PubMed search from 2007 to 2016 and novel drug approvals at the US Food and Drug Administration (FDA) from 2014 to 2016. For the selected drugs, solubility data at acidic and neutral pH were obtained from publications, FDA and European Medicines Agency (EMA) review report, and Japanese interview form. Results: 32 DDI study results with ARAs from 27 drugs having solubility data were obtained. The effect of ARAs on the Cmax or AUC ratio% (with/ without ARAs) decreased with the increasing values of both factors, but the ratio of solubility showed higher values of squared correlation coefficient R-2 (0.75 - 0.78) than the dose (mg)/250 mL/solubility at neutral pH (0.48 - 0.59). Conclusion: Ratio of solubility at acidic pH to that at neutral pH was a good predictor to estimate the effect of ARAs on drug exposure. Prediction of the effect of ARAs on drug exposure using solubility data would help to consider the necessity and timing for conducting a dedicated DDI study with ARAs and contribute to efficient drug development.