Lactic acidosis and severe hepatomegaly with steatosis reported with nucleoside analogs, including fatal cases. Use with caution in risk factors for liver disease (risk may be increased with female gender, obesity, pregnancy or prolonged exposure) and suspend treatment in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or hepatotoxicity. Use associated with myopathy (unexplained muscle aches and/or muscle weakness in conjunction with serum creatine kinase increases) several weeks to months after initiation of telbivudine. Interrupt therapy if myopathy suspected and discontinue therapy if myopathy diagnosed. Severe, acute exacerbation of hepatitis B may occur upon discontinuation. Telbivudine does not exhibit any clinically-relevant activity against HIV type 1. Use caution in moderate to severe renal dysfunction and end stage renal disease. Increased risk of peripheral neuropathy (rarely observed with telbivudine monotherapy) associated with concomitant use of telbivudine and peginterferon alpha-2a in a small study. Symptoms including weakness, paresthesia, and leg pain (disabling in one patient) observed 1-6 months after initiation of therapy. Cross-resistance among hepatitis B antivirals may develop (use caution in patients failing previous lamivudine therapy).