Although adefovir dipivoxil(ADV) has a unique profile of delayed and infrequent resistance in treatment-naive chronic hepatitis B patients,the association of ADV resistance with previous lamivudine(LAM) resistance is not well understood.We compared the emergence of the ADV-resis-tant mutations rtA181V/T and rtN236T between LAM-resistant patients and treatment-naive patients at 48 weeks of ADV monotherapy.Fifty-seven LAM-resistant patients and 38 treatment-n ve patients were treated with 10 mg/d ADV for more than 48 weeks.Both baseline and 48-week blood samples were analyzed for ADV-resistant mutations via restriction fragment mass polymorphism analysis.Antiviral responses were evaluated according to changes in serum HBV DNA(measured via real-time polymerase chain reaction) and alanine aminotransferase(ALT) levels and loss of hepatitis B e antigen(HBeAg) .After 48 weeks,10(18%) of the 57 LAM-resistant patients were found to have developed ADV-resistant mutations,whereas none of the 38 treatment-n ve patients developed such mutations(P .05) .In conclusion,the emergence of the rtA181V/T and rtN236T mutations was more common in LAM-resistant patients than in treatment-n ve patients after 48 weeks of ADV therapy and was associated with reduced antiviral efficacy to drug treatment.
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