Objective Nucleos(t)ide analogues (NAs) na?ve chronic hepatitis B(CHB) patients were given rescue combination therapy after drug resistance to lamivudine or adefovir. Evolution of HBV mutation patterns and its impact on antiviral effects were studied.
Methods Total of 142 na?ve CHB patients treated with lamivudine were randomly divided into two groups when lamivudine resistance occurred. One group was added with adefovir, the other was switched to entecavir and adefovir. Seventy-two na?ve CHB patients treated with adefovir were randomly divided into two groups when adefovir resistance occurred. One group was added with lamivudine, the other was added with entecavir. HBV polymerase reverse transcriptase mutations associated with resistance were analyed before and after 48 weeks of rescue therapy, respectively.
Results The mutation patterns of M204V/I, M204V+L180M were predominantly found in CHB patients after lamivudine resistance. Meanwhile, the entecavir resistance mutation patterns were also detected. Therefore, patients with lamivudine resistance could develop more diverse drug resistance mutations if they were switched to entecavir and adefovir. The mutation patterns of rtA181 were predominantly found in CHB patients after adefovir resistance and rescure therapy with add-on entecavir was more effective than with add-on lamivudine Conclusions Resistance mutation analysis chould help to choose NAs, reduce resistance and ehance antiviral effects.

An analytical method based on solid phase extraction was developed and validated for analysis of adefovir in human plasma. Adefovir-d4 was used as an internal standard and Synergi MAX RP80A (150 mm × 4.6 mm, 4μm) column provided the desired chromatographic separation of compounds followed by detection with mass spectrometry. The method used simple isocratic chromato-graphic condition and mass spectrometric detection in the positive ionization mode. The calibration curves were linear over the range of 0.50–42.47 ng/mL with the lower limit of quantitation validated at 0.50 ng/mL. Matrix effect was assessed by post-column infusion experiment to monitor phospholipids and post-extraction addition experiment was performed. The degree of matrix effect for adefovir was determined as 7.5%and ion-enhancement in five different lots of human plasma was 7.1%and had no impact on study samples analysis with 4.5 min run time. The intra- and inter-day precision values were within 7.7% and 7.8%, respectively, for adefovir at the lower limit of quantification level. Validated bioanalytical method was successfully applied to clinical sample analysis.