Pharmacokinetic and bioequivalence study of enteric-coated omeprazole capsule in healthy Chinese subjects under fasting and fed conditions

This study aimed to evaluate the bioequivalence of a generic enteric-coated omeprazole capsule compared with the reference product (Losec ® ) in healthy Chinese subjects. The fasting study was conducted using a randomized, single-centre, single-dose, two-period, two-sequence crossover design. The fed study was a randomized, single-centre, single-dose, four-period, two-sequence fully replicate crossover design. Healthy subjects were randomized and received either the test or the reference drug under fasting or fed conditions. The plasma concentration of enteric-coated omeprazole capsule at different time points was measured using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Bioequivalence of the two formulations was evaluated through pharmacokinetic parameters and relative bioavailability. In the fasting study, the geometric mean ratios (GMRs) of C max , AUC 0−t , and AUC 0−∞ were 101.33%, 101.81%, and 101.76%, respectively, with all 90% confidence intervals (CIs) falling within the bioequivalence range of 80.00-125.00%. Under fed conditions, high intra-subject variability was observed for C max (CV = 46.79%) and AUC 0−t (CV = 31.61%). The reference-scaled average bioequivalence (RSABE) method showed GMR point estimates of 113.31% for C max and 105.68% for AUC 0−t (both within 80.00-125.00%), with upper 95% confidence bounds below zero. The GMR for AUC 0−∞ was 108.18%, and its 90% CI (102.63-114.02%) also met the bioequivalence criteria. No serious adverse events were reported. The two enteric-coated omeprazole capsules were bioequivalent under both fasting and fed conditions and were well tolerated in healthy subjects. The trial was registered with the China Centre for Drug Testing and Registration ( http://www.chinadrugtrials.org.cn/index.html , 10/05/2022, CTR20221098 and CTR20220627).