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Intron
A and Roferon A
What Is Interferon Alfa?
Which
Patients with Hepatitis B Should Use Interferon?
What
Are the Doses Used?
What
Are the Side Effects of Treatment?
Intron
A Prescribing Information 
| WARNING
- Alpha interferons, including INTRON® A, cause or aggravate
fatal or life-threatening neuropsychiatric, autoimmune, ischemic,
and infectious disorders. Patients should be monitored closely
with periodic clinical and laboratory evaluations. Patients
with persistently severe or worsening signs or symptoms of these
conditions should be withdrawn from therapy. In many but not
all cases these disorders resolve after stopping INTRON A therapy.
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What
Is Interferon Alfa?
Natural
interferon is a protein produced by the body's cells in response
to viral infections. There are three types: alfa, beta and gamma.
Commercially-produced (genetically-engineered) interferon alfa mimics
the activity of naturally-occuring interferon alfa produced by the
body, although the mechanism of action of the drug is not well understood.
Intron A (interferon alfa-2b) is one commercial form of interferon
approved by the US Food and Drug Administration for the treatment
of Hepatitis B and C.
Roferon A (interferon alfa-2a), and Infergen ("consensus"
interferon) are also FDA-approved for treatment of chronic hepatitis
C, but not for chronic hepatitis B.
Which Patients with Hepatitis B Should Use Interferon?
Less
than 50% of patients with chronic hepatitis B infection are eligible
for interferon therapy. Patients should have infection documented
for at least six months, elevated liver enzymes (AST or SGOT, and
ALT or SGPT tests) and an actively replicating virus in their blood
(hepatitis "e" antigen [HBeAg] and/or hepatitis B virus
DNA [HBV DNA] positive tests).
Patients with normal liver enzymes are less likely to respond to
therapy. Patients with low hepatitis B virus DNA levels and elevated
liver enzymes are more likely to benefit than those with high HBV
DNA levels.
A biopsywhere a needle is inserted into the liver to obtain
a small sample of tissueis helpful to determine liver damage
prior to treatment. Patients with acute infection, cirrhosis
or other major medical problems should not be treated.
What
Are the Doses Used?
The FDA-approved dose of standard interferon alfa for treatment
of hepatitis. FDA-approved treatment for hepatitis B is five million
units daily for 16 weeks. The dose may be modified for significant
side effects.
However, lower doses may result in lower rates of response. Higher
doses, more frequent doses, longer therapy, and combination therapies
are being tested.
What
Are the Side Effects of Treatment?
The most common serious side effect is depression, particularly
in patients with a prior history. Most patients will have muscle
aches, fatigue and low grade fevers. These can be minimized by taking
low doses of acetaminophen (e.g. Tylenol) at night. Nausea and diarrhea
are common as is irritation of the skin at the injection site.
Patients may experience significant weight loss, and if this occurs
the dose should be adjusted. Patients often complain of irritability
and headaches. A small number of patients may develop thyroid disease.
Normal thyroid function should be documented prior to treatment.
Hair loss is not uncommon, but usually reversible. Few side effects
are severe or persist after treatment.
When
Is Treatment Not Indicated?
Patients with chronic hepatitis B or C, with fluid in
the abdomen (ascites), bleeding from dilated veins in the esophagus
(variceal bleeding), or mental confusion (encephalopathy) should
be treated only in a clinical trial.
Others not suitable for treatment are those with symptomatic heart,
lung or kidney disease, with human immunodeficiency virus (HIV)
infection or organ transplant recipients on prednisone, cyclosporine
and FK-506 and patients on antidepressants or with a history of
suicide attempts.
Interferon should not be given to women considering pregnancy, nor
to the intended father. Patients with active substance abuse (alcohol
or illegal drugs) should not be offered this therapy.
What
Can Be Expected from Treatment?
Approximately
40%-50% of patients with chronic hepatitis C receiving full dose
therapy will have a normalization of their liver enzymes, usually
by the third month. With normal liver tests, the virus may become
undetectable in blood. If no response is seen by three months, most
researchers advocate stopping therapy.
A few patients who respond to therapy may see their liver enzymes
rise towards the end of treatment. The reason for this is unknown.
When interferon is stopped after six months, more than half of the
patients with hepatitis C who have responded will experience a rise
in their liver tests. Patients will usually respond again if given
further therapy. Therefore, 10%-15% will have a long lasting positive
response. Longer treatments will likely result in longer positive
responses. However, there is no evidence that this affects the relapse
rate when treatment is stopped. Few patients will eradicate the
virus using this therapy alone.
What
Happens if Interferon Is Not Given?
The
long term prognosis of hepatitis C is poorly understood. However,
hepatitis C is generally a slowly progressive disease, with evolution
over years if not decades. There is no proof that six months of
treatment with interferon alters this.
The changes vary from mild chronic hepatitis (least amount of liver
damage) to moderate or severely active chronic hepatitis, with or
without fibrosis or cirrhosis (most amount of liver scar damage).
It is not known who will develop complications including chronic
liver disease, liver failure and liver cancer.
What New Drugs Are Available?
Much
is unknown about treatment with interferon. Therefore, when possible,
patients should consider participating in clinical trials.
Different kinds of interferons and other new drugs, by themselves
or in combination with other drugs, are being evaluated for both
hepatitis B and C.
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