Pegasys Medication Side Effects

If you've been prescribed a medication called Pegasys to treat chronic hepatitis C, chronic hepatitis B, or another liver problem, you may be wondering about the drug's side effects.

The most common side effects for peginterferon (such as Pegasys or PegIntron) are:

  • fatigue
  • headache
  • fever
  • muscle pain
  • 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.

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How Side Effects Are 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 the side effects are. 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

This list of side effects is arranged in order of frequency. This means that more people in the study group reported the side effects at the top of the list than at the bottom 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, which can then help prepare their patients for it.

Should You Be Concerned?

You should know and understand these side effects.

It's helpful to know the side effects of medications so that you can better prepare for them. For example, if you have trouble with depression, taking this medication could worsen your usual episodes. Almost 20 percent 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.

However, you should not be discouraged by these side effects. Every medication will have some unwanted effects, but taking this drug gives you the best chance of successful treatment in exchange for 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 You 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 U.S. The source of this list is from the Pegasys package insert which can be found online at the drug manufacturer's website or on the website of U.S. Food and Drug Administration (FDA).

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.

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