ENTECAVIR IS A NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITOR, STRUCTURALLY RELATED TO GUANOSINE WITH SELECTIVE ANTIVIRAL ACTIVITY AGAINST HEPATITIS B VIRUS.
ENTECAVIR IS PHOSPHORYLATED INTRACELLULARLY TO THE ACTIVE TRIPHOSPHATE FORM WHICH COMPETES WITH DEOXYGUANOSINE TRIPHOSPHATE, THE NATURAL SUBSTRATE OF HEPATITIS B VIRUS REVERSE TRANSCRIPTASE, THEREBY INHIBITING EVERY STAGE OF THE ENZYME'S ACTIVITY.
ENTECAVIR HAS NO ACTIVITY AGAINST HIV.