Hepatitis C Home > Pegasys Side Effects

Muscle aches, fatigue, and headaches were some of the most commonly reported side effects of Pegasys during clinical trials. Although not everyone will have reactions to this drug, most people will experience some type of side effect. Make sure you are aware of the reactions that may require medical treatment, such as a severe headache, vision or speech changes, or suicidal thoughts or behaviors.

An Introduction to Pegasys Side Effects

Just like any medicine, Pegasys® (peginterferon alfa-2a) can cause side effects. Most people using this drug will develop some sort of adverse reaction. In many cases, these problems are merely bothersome and not usually dangerous. In other cases, they may be so severe or dangerous that the medication must be stopped.
(This article covers many, but not all, of the possible side effects with Pegasys. Your healthcare provider can discuss a more complete list with you.)

Common Side Effects of Pegasys

Pegasys has been studied extensively in clinical trials. In these studies, some of the people were treated with Pegasys, while others were treated with other similar interferon medications. The side effects that occurred in the two groups were carefully documented and compared.
In most of the studies, people were also treated with ribavirin (Rebetol®), which helps improve the effectiveness of interferon medications when treating hepatitis C. The information here includes only the data from Pegasys used alone, without ribavirin.
In these studies, the most common Pegasys side effects included:
  • Flu symptoms, such as fatigue, fever, and muscle aches -- in up to 81 percent of people
  • Fatigue -- up to 56 percent
  • Headache -- up to 54 percent
  • Skin reaction at the injection site -- up to 42 percent
  • Muscle pain -- up to 37 percent
  • Fever -- up to 37 percent
  • Shaking or chills -- up to 35 percent
  • Joint pain -- up to 28 percent
  • Nausea and vomiting -- up to 24 percent
  • Hair loss -- up to 23 percent
  • Low neutrophils (a type of white blood cell) -- up to 21 percent
  • Irritability, anxiety, or nervousness -- up to 19 percent
  • Insomnia -- up to 19 percent
  • Depression -- up to 18 percent
  • Decreased appetite/eating less -- up to 17 percent
Other common side effects of Pegasys, occurring in 3 percent to 16 percent of people, included:
  • A rash
  • Itching
  • Underactive thyroid (hypothyroidism)
  • Pain
  • Diarrhea
  • Abdominal (stomach) pain
  • Dry mouth
  • Low lymphocytes (a type of white blood cell)
  • Anemia
  • Low blood platelets
  • Weight loss
  • Back pain
  • Dizziness
  • Memory problems
  • Problems concentrating
  • Mood changes
  • Shortness of breath
  • Coughing
  • Dry skin
  • Increased sweating
  • Dermatitis
  • Blurred vision.
Written by/reviewed by:
Last reviewed by: Kristi Monson, PharmD;
Last updated/reviewed:
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