What Is Interferon?
Interferon is a natural substance produced by your body in response to a viral infection. It helps the body distinguish between cells infected by the virus and non-infected cells, targeting infected cells for destruction. In this way, Interferon helps you recover from viral infections. In the process, it may cause some side effects such as achy sore muscles and joint pain that we associate with the flu.
A common type of viral infection is viral hepatitis, a serious liver infection. For unknown reasons, a virus in the liver often becomes invisible to the immune system. If your body can't see the virus, it can't destroy it. This allows the virus to multiply within your liver and the infection becomes chronic and more severe. Scientists have learned that if they gave synthetic Interferon to a person with chronic viral hepatitis, they could increase the immune system's ability to detect, or see, the infection. Think of Interferon like "eyeglasses for your immune system." Once your body can see the virus, it can usually destroy it. Interferon also helps patients with viral hepatitis by directly suppressing the formation of new virus particles within the liver.
Who Should Receive Interferon?
As mentioned above, chronic viral hepatitis is an inflammation of the liver caused by a persistent viral infection in the body. The different types of hepatitis have been given letter names such as A, B, C, etc. Certain patients with Chronic Hepatitis B or Chronic Hepatitis C are candidates for Interferon therapy. Your doctor can best decide if this therapy is needed or likely to help. However, some generalizations are possible:
Less than 50% of Chronic Hepatitis B carriers are eligible for therapy. The infection must be present for greater than six months. Certain blood tests called liver enzymes (ALT and AST) serve as indicators of liver inflammation. These enzyme levels should be elevated greater than 1.5 times normal since patients with normal liver enzymes, so called "healthy carriers," rarely if ever respond to Interferon. Lastly, evidence of active viral replication should be present. Active viral replication can be assessed with special blood tests, which detect the viral antigen (HBeAg) or viral DNA. If you have Chronic Hepatitis B and you meet these three criteria; you may be eligible for Interferon.
Who Should Not Receive Interferon?
Many more Chronic Hepatitis C patients are candidates for Interferon treatment. You may be eligible, if there is evidence of chronic infection, increased liver enzymes, and the absence of decompensated cirrhosis (liver failure).
Contraindications to Interferon include: ongoing abuse of alcohol or drugs, pregnancy, low blood count, anemia, advanced or decompensated cirrhosis, major depression, and a past history of suicide attempts or an autoimmune disease such as Lupus.
What Types of Interferon are Available?
There are two types of Interferon currently available. Interferon-alpha 2a or 2b is the compound that has been extensively used and tested to this point. Though the dose varies, patients with Chronic Hepatitis C usually receive 3 million units 3 times per week. Individuals with Chronic Hepatitis B receive a higher dose of 10 million units 3 times per week. The duration of therapy is often 48 weeks for Hepatitis C, and 16 weeks for Hepatitis B.
A newer formulation just released on the market is called Pegylated Interferon. This drug was developed in response to the rapid breakdown, fall in blood levels, and subsequent loss of antiviral effect seen with interferon given 3 times per week. By attaching a molecule called P.E.G to Interferon-alpha 2a or 2b, researchers were able to slow its breakdown by the body. More consistent drug levels were achieved with the need to only give the drug once per week. Above and beyond the convenience of once a week injection, the PEG formulations had greater viral clearance rates. It is expected with time that this newer formulation will replace entirely the older interferon-alpha 2a/2b.
How Is Interferon Administered?
Interferon, unfortunately, must be given as an injection similar to insulin in diabetics. Detailed instructions on self-administration will be given by a nurse when you first begin. Your first injection will be observed by the nurse for proper technique and for side effects.
What Are The Side-Effects?
The most common side effect is that of flu-like symptoms with the first few injections. These symptoms can be reduced by pretreatment with Tylenol or Advil, and giving injections late in the evening, so you sleep through them. Drink plenty of water. As your body gets accustomed to the Interferon, these side effects decrease after a few weeks of therapy. A common, and more serious side effect is depression; particularly if there is a history of depression. If you suffer from depression, or develop depression while on therapy, be sure to inform your doctor. Typical symptoms of depression are unexplained sadness, spells of crying, insomnia, early morning awakening, loss of interest in food, sex, hobbies, etc.
Interferon may affect the bone marrow where red and white blood cells are produced. Changes in red and white cell blood counts can occur and sometimes can be severe. Frequent lab tests will be required to monitor these values and adjust or stop treatment if necessary. Severe changes in your blood values could predispose you to infections and/or bleeding. Rarely, (less than 1% of cases), your thyroid gland may become over or underactive. This will also be monitored by blood tests. Extreme fatigue or insomnia, irritability, or excessive sweating may be signs of these problems. Other troublesome side effects may include nausea, diarrhea, thinning of hair, irritation at injection site and weight loss. For the most part these are reversible with time and occasional withholding of the medication.
What's The Expected Cure Rate?
For Hepatitis C, the "cure rate," which is defined as the inability to detect virus in the blood 6 months after stopping therapy, varies significantly depending on a number of patient, viral and drug regimen characteristics. The most important factor appears to be the genetic makeup or genotype of your virus. Unfortunately, genotypes 1a and 1b, the most common types in North America, have the worst response rate, with only 19% and 25-40% in interferon and pegylated interferon respectively. Adding a second anti-viral drug, ribavirin, increases the response rate to between 35 and 60 %. Genotypes 2 or 3 carry a much higher rate of eradication, ( 60% or more). Some authorities are predicting that combining PEG interferon with the drug ribavirin, will result in eradication rates close to 90 - 100%. This drug combination is currently undergoing extensive study.
Hepatitis B is associated with a 35% response rate as defined by normalization of liver enzymes and loss of markers of active viral infection. Such a response signifies a decrease in your ability to spread the virus to others and also a decrease in the liver damage associated with viral infection - conversion to the so called healthy carrier state. Note: complete elimination of the Hepatitis B virus is rare.
What If You Don't Take Interferon?
The natural history of Hepatitis C is just now being worked out. We do believe that in most patients the disease progresses slowly over years to decades. The average time from infection to serious disease is 10 years. Liver cirrhosis takes about 20 years and an increased risk of liver cancer is seen after about 30 years. Note that some patients may have a more rapidly progressive disease with cirrhosis within 3 to 5 years from onset of infection. A liver biopsy is often helpful to stage the disease, evaluate the amount of inflammation and likelihood of progressive disease. A repeat biopsy may be recommended in 2 to 3 years for patients with mild changes for whom Interferon has not been recommended, or in those who choose not to have therapy. Abstinence from alcohol plays an important role in treatment.
Hepatitis B infection is a more aggressive illness with progression to cirrhosis over years rather than decades. Patients who are candidates for Interferon with chronic active hepatitis due to hepatitis B should strongly consider a course of therapy.
Managing Side Effects of Therapy
- Tylenol or ibuprofen can be used to prevent or relieve fever and headache.
- Bedtime or early evening injections may allow you to sleep through flu-like symptoms.
- Conserve your energy - get plenty of sleep.
- Drink plenty of fluids before and during therapy - at least 8 glasses daily.
- Eat balanced meals with an adequate intake of calories.
- Focus on the positive.