Serious side effects

Some peginterferon alfa and ribavirin side effects are serious enough to require close monitoring by your doctor. If necessary, you may have to reduce your medication dosage or stop treatment completely. These serious side effects include:

• A sharp reduction in red blood cells (anemia), which is particularly dangerous for people with heart disease or at high risk of heart disease
• Suicidal thoughts and impulses, particularly in people with a history of depression, addiction or both
• A low level of clotting cells in your blood (thrombocytopenia), potentially leading to serious bleeding problems, particularly in those with liver disease
• Eye problems — specifically, abnormalities in the light-sensitive lining at the back of the eye (retina), particularly in people with diabetes or high blood pressure
• Inflammation of tissue in the air sacs and lining of the lungs (interstitial pneumonitis), which can severely restrict breathing in a short time
• Increased or new signs and symptoms of thyroid disease (hypothyroidism), a condition that can be hard to distinguish from the most common treatment side effects, such as fatigue
• Flares of existing autoimmune conditions, such as rheumatoid arthritis, lupus and psoriasis

Exposure to ribavirin during pregnancy can cause abnormalities in the developing baby. Women should have pregnancy tests before and periodically during ribavirin treatment. Similarly, men considering ribavirin treatment should take precautions to avoid exposing their female partners' unborn children to the drug by:

• Abstaining from sex with any woman who may be pregnant
• Postponing treatment until a pregnant partner has given birth
• Using two forms of birth control every time they have sex during treatment