Entecavir

Entecavir inhibits HBV DNA polymerase. Effective orally, the drug undergoes renal elimination in part via active tubular secretion. Clinical efficacy is similar to that of lamivudine and there is cross-resistance between the 2 drugs. The drug causes headache, dizziness, fatigue, and nausea. It is a guanosine analog approved for the treatment of HBV infections. Following intracellular phosphorylation to the triphosphate, it competes with the natural substrate, deoxyguanosine triphosphate, for viral reverse transcriptase. Entecavir has been shown to be effective against lamivudine-resistant strains of HBV. Liver inflammation and scarring are improved. Entecavir need only be given once a day. Entecavir undergoes both glomerular filtration and tubular secretion. Very little, if any, drug is metabolized. Renal function must be assessed periodically, and drugs that have renal toxicity should be avoided. Patients should be monitored closely for several months after discontinuation of therapy because of the possibility of severe hepatitis.