The high worldwide prevalence of chronic viral hepatitis, as well as i
ts progressive course, have led to the performance of multiple clinica
l studies, The natural history of the disease is different depending o
n the infecting virus; thus, the evolution to liver cirrhosis and/or h
epatocellular carcinoma for the hepatitis B, C and delta (D) viruses i
n chronic hepatitis is 15, 20 and 75%, respectively, Different therape
utic agents have been used in attempts to modify the natural course of
these diseases, interferon-alpha (IFN alpha) having proved to be the
most effective. In 30 to 50% of patients, treatment with IFN alpha has
achieved inhibition of viral replication, as well as normalisation of
aminotransferase levels. Moreover, in a majority of patients, histolo
gical improvement is observed, principally in piecemeal necrosis and p
ortal inflammation. The dosage currently recommended for treatment of
chronic hepatitis B is 30 to 35MU weekly for a minimum of 4 months; wh
en there is a co-existing delta virus infection, the total dosage empl
oyed should be greater. For hepatitis C, the minimum effective dosage
is 9MU weekly, and a treatment duration of 12 months is recommended. T
he administration of IFN alpha produces a series of dose-dependent adv
erse effects, which are reversible on suspension of the medication. Th
e most frequent of these adverse reactions is the 'flu-like' syndrome,
which is self-limited and generally well tolerated. Secondary haemato
logical alterations (leucopenia and thrombocytopenia) are the most fre
quent cause of reduction in dosage or suspension of treatment, althoug
h the latter is not normally necessary. The proportion of patients req
uiring dosage modification or suspension of treatment fluctuates betwe
en 5 and 15%. Taking the evolution of chronic hepatitis into account,
there can be no doubt that all patients with this disease should be of
fered treatment. At present, the drug of choice is IFN alpha, as it sl
ows disease progression and it is generally well tolerated.