Pegylated interferon is an interferon molecule with polyethylene glycol (PEG) attached to it. The addition of PEG to the interferon molecule enables the interferon to be released slowly into the body, thus prolonging its action. Whereas interferon alone requires dosing three times weekly, pegylated interferon requires dosing only once weekly.
Interferon is a protein manufactured by the body. When an infection is present, the body increases interferon production to fight the invading virus or bacteria. For some diseases, such as hepatitis, injecting interferon boosts the ability of the body to fight off the infection. Interferon does not attack the virus directly. Rather, it helps the body's immune system to fight the foreign organism, prevent the virus from reproducing, eliminate infected cells and prevent healthy cells from becoming infected.
The PEG portion of the molecule acts as a barrier around the interferon so that the body clears the interferon more slowly than it would clear nonpegylated interferon. Interferon does not react with PEG, and PEG does not alter the effectiveness of the interferon. Pegylated interferon is used for the treatment of acute and chronic hepatitis C infection. It is usually combined with ribavirin.
The primary benefit of this compound is the length of time it remains in the bloodstream, compared with nonpegylated interferon. Once-a-week dosing provides a sustained response. The compound has been shown to be more effective against hepatitis C virus compared with nonpegylated interferon.
Pegylated interferon is associated with a number of side effects. The most commonly reported side effects are flu-like symptoms, such as fever, chills and muscle aches. Other common side effects include nausea and vomiting, headache, irritability, fatigue, loss of appetite and fluctuating blood sugar levels that might lead to diabetes. Skin rashes and dry and itchy skin are also common side effects.
Serious side effects have been reported in association with this type of therapy. Side effects include depression, mental confusion, infection and problems with blood pressure, heart, liver, lungs, immune system, thyroid and eyes. Rarely, suicide has been reported among people receiving pegylated interferon therapy.
This compound has also been associated with decreases in neutrophils, a type of white blood cell, and platelets, which help the blood to clot. These serious side effects might require dose reduction. Most side effects disappear when this therapy ends.
Although pegylated interferon plus ribavirin is an effective treatment for hepatitis C, pegylated interferon does not have the same effect in every person. The effectiveness of the treatment depends on the particular strain of hepatitis C virus. For example, this treatment is more effective against strains 2 and 3 compared with strains 1a or 1b. Additionally, the treatment is less effective in African Americans than in people of other ethnicities.