to interferon therapy, side-effects with lamivudine, telbivudine, entecavir,
adefovir or tenofovir therapy occur very rarely.
Headache, fever, skin rash, general malaise,
gastrointestinal complaints, sleeplessness, cough and, in some cases,
inflammation of the pancreas have been described.
When treatment is carried out with adefovir and
tenofovir, kidney function should be monitored regularly. Compared to other
antivirals, the development of resistance to lamivudine can occur more
frequently and sooner. The rate of the development of resistance with
lamivudine is 30%, with telbivudine 15%, with entecavir, adefovir and tenofovir
less than 2% after two years when used as a single drug (monotherapy). After
five years of treatment, the rates of resistance are about 70% (lamivudine), 28%
(adefovir) and less than 1% (entecavir).
The rate of development of resistance to entecavir,
however, is higher in people who have already developed resistance to
lamivudine, so that the use of entecavir is not generally recommended with
existing lamivudine resistance. Fortunately, lamivudine and
telbivudine-resistant hepatitis B viruses respond to adefovir or tenofovir and,
vice versa, adefovir-resistant viruses to lamivudine, telbivudine and entecavir.
Tenofovir-resistant viruses have not been clinically
observed so far.
When resistance arises, two suitable (not 'cross-resistant') medications should be taken together (combination
therapy). If patients have an insufficient virological response to one
antiviral drug, many doctors add a suitable second antiviral drug early on, so
that the development of resistance is avoided right from the start.