[Pharmacological properties and clinical efficacy of entecavir monohydrate (Baraclude Tablet 0.5 mg), an anti-HBV drug]

Pooled model-based approach to compare the pharmacokinetics of entecavir between Japanese and non-Japanese chronic hepatitis B patients

This study evaluated the population pharmacokinetics (PK) of entecavir in Japanese patients with chronic hepatitis B infection enrolled in 2 Japanese phase IIb clinical trials and compared them to non-Japanese patients enrolled in global phase II trials. The objectives were to identify significant and clinically meaningful covariate effects on entecavir population pharmacokinetic parameters and assess whether differences exist between Japanese and non-Japanese patients. A total of 843 observations were obtained from 142 patients who received once daily administration of entecavir at 0.1, 0.5, and 1.0 mg doses in the 2 Japanese studies. Consistent with findings in non-Japanese patients, creatinine clearance estimated with ideal body weight (ICrCL) was found to be statistically significant for clearance in a 2-compartment model. Also, the entecavir dose was identified as a covariate on intercompartmental clearance. Age, gender, and hepatic function were not identified as covariate for clearance. The estimated population average of oral clearance in a typical patient with a reference ICrCL value of 100 mL/min was 26.4 L/h (interindividual variability: 19.4%). This model-based analysis indicates that the PK of entecavir are similar in Japanese and non-Japanese chronic hepatitis B patients.

LC-ESI-MS/MS method for the quantification of entecavir in human plasma and its application to bioequivalence study

Liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) was used for a quantitative estimation of entecavir (EV) in human plasma using lamivudine (LM) as internal standard (IS). The method herein described is simple, sensitive, and specific. Chromatographic separation was performed on XBridge-C18, 4.6 mm × 50 mm, 5-μm column with an isocratic mobile phase composed of 10 mM ammonium hydrogen carbonate (pH 10.5):methanol (85:15 v/v), pumped at 0.3 ml/min. EV and LM were detected using proton adducts at m/z 278.1→152.1 and 230.2→112.0 in multiple reaction monitoring (MRM) positive mode. Solid phase extraction method was employed in the extraction of EV and LM from the biological matrix. This method was validated over a linear concentration range of 50.0-20000.0 pg/ml with a correlation coefficient (r) ≥0.9983. Intra and inter-day precision of EV was found within the range of 1.2-4.2 for EV and 4.4-4.5 for LM. EV was stable throughout three freeze/thaw cycles, bench top and postoperative studies. This method was successfully used in the analysis of plasma samples following oral administration of EV (0.5 mg) in 26 healthy human volunteers.