Background/aims: Some patients receiving adefovir at the approved dose of 10 mg daily for chronic hepatitis B have a "suboptimal" virological response characterized by a slow and moderate decrease in viral replication.
Methods: We assessed the efficacy and safety of adefovir 20 mg daily in patients with hepatitis B e antigen-positive chronic hepatitis B resistant to lamivudine and a suboptimal virological response to adefovir 10 mg daily add-on.
Results: No amino acid substitutions known to confer adefovir resistance were found in these patients. In the five treated patients, the switch from 10 mg to 20 mg of adefovir daily significantly improved antiviral efficacy (-1.78+/-0.28 log international units/mL versus -3.73+/-0.51 log international units/mL, respectively, p=0.0039), and alanine aminotransferase levels normalized in all but one of the patients. No signs of renal dysfunction occurred.
Conclusions: These results suggest: (i) that suboptimal responses to adefovir 10 mg daily are due to underdosing; and (ii) that increasing the adefovir dose to 20 mg daily is beneficial and safe in patients with lamivudine-resistant HBV and a suboptimal response to adefovir 10 mg daily, especially when alanine aminotransferase levels are elevated and/or the liver disease is severe or rapidly progressive. Careful monitoring of renal function is necessary.