Effect of Omeprazole Administration on the Pharmacokinetics of Oral Extended-release Nifedipine in Healthy Subjects.

Oral extended-release (ER) dosage forms have been used to sustain blood drug levels, reduce adverse events, and improve patient compliance. We investigated potential effect of comedication on pharmacokinetic exposure of nifedipine ER products with different formulation designs and manufacturing processes. A clinical study compared a generic version of nifedipine ER tablet with pH-dependent dissolution behavior with an osmotic pump product with pH independent drug release under fasting condition. In this study, two nifedipine tablet products were tested with or without short term omeprazole comedication in healthy subjects. Seven-day administration of omeprazole before nifedipine dosing significantly increased the gastric pH, and subsequently increased the geometric least square (LS) means of AUC and C of nifedipine to 132.6% (90% CI 120.6%-145.7%) and 112.8% (90% CI 100.8%-126.3%) for pH-dependent ER tablets, and 120.6% (90% CI 109.7%-132.5%) and 122.5% (90% CI 113.7%-131.9%) for the pH-independent ER tablets, respectively. Similar extent of increase in AUC and C was confirmed in the subpopulations whose gastric pH was ≥ 4 or ≤ 3 in subjects with or without omeprazole administration. Given that similar increases in drug exposures were observed for both pH-dependent and pH-independent nifedipine formulations and the geometric LS mean ratios were between 112 and 133% with and without short term omeprazole comedication, the gastric pH may have limited effects on omeprazole-induced nifedipine PK changes on the tested formulations. The inhibition of cytochrome P450 3A4 activity may play a significant role causing nifedipine exposures change for both formulations, which would warrant additional assessment.