Side Effects from Taking Pegasys

The most common side effects for peginterferon (such as Pegasys or PegIntron) are fatigue, headache, fever, muscle pain and chills. However, other possible side effects are listed below. Although these side effects are specifically for Pegasys (a brand name peginterferon alfa-2a drug for treating hepatitis C and sometimes hepatitis B), they are similar to any other peginterferon such as PegIntron.

How Are These Side effects Determined?

Before a drug (such as Pegasys) can be licensed as an approved treatment for hepatitis B and hepatitis C, it has to be tested in clinical trials. Clinical trials are scientific studies that determine if the drug is safe and what are the side effects. The side effects listed below were determined by treating 559 people with 180 micrograms of Pegasys for 48 weeks. The number listed after each side effect is the percentage of the 559 people in the clinical trial who reported that particular side effect.

How to Understand This List of Side Effects

This list of side effects is arranged in order of frequency, which means that more people in the study group reported the side effects at the beginning of the list than at the end of the list. Since peginterferon will react a little differently in each person, this list should be considered only as a general guide. However, by using the list below, doctors know that about half of their patients on peginterferon will suffer fatigue and can then help prepare them for this.

Should I Be Concerned about These Side Effects?

You should absolutely know and understand these side effects. Sometimes it's helpful to know what the side effects are so that you can better prepare for them. For example, if you have trouble with depression, taking this medication could worsen your usual episodes because almost 20% of people report depression while on this medicine. By knowing that depression is a potential side effect, you and your doctor can discuss solutions such as prescribing antidepressants before you begin this treatment.

It's also important not to be discouraged by these side effects. Every medication will have some unwanted effects, but taking this drug gives you the best chance of a successful treatment in exchange for having side effects. As potentially better treatments are introduced, you can compare their effectiveness against their side effects and, with your doctor, make an informed decision on your treatment.

Where Do I Get This Information?

The side effects (also called adverse reactions) of every drug must be determined through extensive clinical trials before the drug can legally be sold in the United States. The source of this list is from the Pegasys package insert which can be read from the drug manufacturer or the US Food and Drug Administration.

A Complete List of Peginterferon Side Effects
Side Effect	Percentage Reporting
Fatigue	56%
Headache	54%
Fever (pyrexia)	37%
Muscle pain (myalgia)	37%
Shivering (Rigors)	35%
Joint pain (arthralgia)	28%
Nausea/Vomiting	24%
Hair loss (alopecia)	23%
Injection site reaction	22%
Neutropenia	21%
Irritability and nervousness	19%
Trouble sleeping (insomnia)	19%
Depression	18%
Loss of appetite (anorexia)	17%
Diarrhea	16%
Dizziness (not vertigo)	16%
Belly pain	15%
Itchiness (pruritus)	12%
Pain	11%
Resistance Mechanism Disorders	10%
Back pain	9%
Dermatitis	8%
Trouble concentrating	8%
Dry mouth	6%
Increased sweating	6%
Loss of some memory	5%
Rash	5%
Thrombocytopenia	5%
Blurry vision	4%
Cough	4%
Dry skin	4%
Shortness of breath (dyspnea)	4%
Weight loss	4%
Changes in mood	3%
Hypothyroidism	3%
Lymphopenia	3%
Anemia	2%
Eczema (general skin inflammation)	1%
Shortness of breath on exertion	<1%*
Upset stomach (dyspepsia)	<1%*
*This means that less than 1% of the study group reported this side effect.