by Alison Bowler

Created on: July 16, 2011   Last Updated: July 18, 2011

Pegasys is the registered trade name for the recombinant form of alfa-2a interferon known as Peginterferon alfa-2a. Alfa-2a interferon is a protein produced by the human immune system in response to certain viral infections. The recombinant version in the drug Pegasys is produced by inserting the human gene coding for alfa-2a interferon into the bacterium Escherichia coli and recovering the protein from the bacterial culture.

This drug is useful in the treatment of chronic cases of hepatitis caused by the Hepatitis B (HBV) and Hepatitis C (HCV) viruses. Chronic infections with HBV or HCV may lead to permanent even fatal liver damage. The use of Pegasys to treat HBV or HCV requires monitoring by a suitably qualified medical practitioner as some case may not respond to treatment and adverse side effects may occur in some patients. It is often used in conjunction with another antiviral drug called ribavirin.

The most severe side effect seen is an allergic reaction to the drug. This may cause hives; difficulty breathing or swelling of the face, lips, tongue or throat. Any person developing such symptoms requires immediate medical attention.

Less severe symptoms that still requires ceasing treatment and notification of the patient's doctor include mental disturbances such as confusion, severe depression, thoughts of self harm, unusual anxiety, aggression, or other thoughts or behaviors. Patients with pre-existing psoriasis who notice an exacerbation of their symptoms should stop taking Pegasys and contact their doctor.

Other side effects, which also require immediate notification and cessation of medication, are-

- Sudden numbness, weakness, or loss of balance;
- Flu-like symptoms such as body-aches, fever or chills;
- Body aches, flu symptoms;
- Easy bruising or bleeding;
- Chest pain, uneven heartbeats, pain that spreads to the arm or shoulder, this may be combined with nausea, sweating and general ill feeling;
- Cough, stabbing chest pain, shortness of breath;
- Severe pain in the upper stomach, which spreads to the back and a fast heart rate;
- Blurred vision, headache or pain behind the eyes
- Fever with bloody diarrhea and a severe stomach pain.

There are a number of less severe side effects from taking Pegasys. Such side effects include -

- Increased hunger, thirst, or need to urinate;
- Mild anxiousness or irritability;
- Headaches, muscle or joint pains;
- Gastrointestinal symptoms such as nausea, vomiting, dry mouth or loss of appetite;
- Hair loss, weight loss;
- Insomnia;
- Itchy skin:
- Pain, redness, swelling, or irritation at the injection site.

Any side effects experienced while taking Pegasys should be reported to the prescribing physician. Patients experiencing minor side effects may still benefit from continuing with the medication with appropriate medical supervision.

Certain pre-existing medical conditions may preclude the tendency to develop side effects to Pegasys. Taking of a complete medical history will help a medical practitioner to identify patients for whom this may be a problem. Some conditions that may be relevant in this concern include HIV infection, autoimmune disorders (such as lupus or psoriasis) and mental disorders.

Pegasys may improve the condition of patients with chronic viral hepatitis. However, it is a powerful drug and Pegasys should only be used with qualified medical supervision to monitor both its efficacy and side effects.

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