SIDE EFFECTS: See also Warning section. Most people have flu-like symptoms such as headache, tiredness, fever, chills, and muscle aches, but these usually decrease after the first few weeks of treatment. You can lessen these side effects by injecting this medicine at bedtime and using fever reducers/pain relievers such as acetaminophen before each dose. Ask your doctor or pharmacist for more information. Nausea, vomiting, diarrhea, dry mouth, loss of appetite, dizziness, trouble sleeping, or redness/swelling at the injection site may also occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly. Tooth and gum problems may sometimes occur during treatment. Having a dry mouth can worsen this side effect. Prevent dry mouth by drinking plenty of water or using a saliva substitute. Brush your teeth well at least twice a day and have regular dental exams. If you vomit, rinse your mouth afterward to lessen the chance of tooth and gum problems. Temporary hair loss may occur. Normal hair growth should return after treatment has ended. Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects. Tell your doctor right away if you have any serious side effects, including: easy bleeding/bruising, feeling too hot or cold (more than others around you), gradual change in weight (without a change in diet or exercise), unusually slow/fast/pounding heartbeat, increased thirst/urination, black/tarry stools, signs of liver problems (such as nausea/vomiting that doesn't stop, loss of appetite, stomach/abdominal pain, yellowing eyes/skin, dark urine), numbness/tingling of arms/legs. Get medical help right away if you have any very serious side effects, including: chest pain, seizures, symptoms of a stroke (such as weakness on one side of the body, trouble speaking, confusion), vision changes (such as blurred vision, partial loss of vision). This drug may cause serious mental/mood changes that may get worse during treatment or after your last dose. Tell your doctor right away if you have symptoms such as confusion, depression, thoughts of suicide or hurting others, unusual irritability, or aggressive behavior. This medication may lower your ability to fight infections. This may make you more likely to get a serious (rarely fatal) infection or make any infection you have worse. Tell your doctor right away if you have any signs of infection (such as sore throat that doesn't go away, fever, chills, cough). A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing. This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist. In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch. In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

PRECAUTIONS: See also Warning section. Before using peginterferon alfa-2a, tell your doctor or pharmacist if you are allergic to it; or to polyethylene glycol (PEG); or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details. Before using this medication, tell your doctor or pharmacist your medical history, especially of: other liver problems (such as autoimmune hepatitis), mental/mood disorders (such as depression, psychosis, suicidal thoughts), autoimmune disorders (such as rheumatoid arthritis, lupus, psoriasis), bleeding/blood problems, diabetes, heart problems, high blood pressure, intestinal problems (such as colitis), kidney disease, lung problems (such as chronic obstructive pulmonary disease-COPD), pancreatitis, high triglyceride levels, thyroid problems, drug or alcohol use/abuse. This medication can make you more likely to get infections or may worsen any current infections. Avoid contact with people who have infections that may spread to others (such as chickenpox, measles, flu). Consult your doctor if you have been exposed to an infection or for more details. Do not have immunizations/vaccinations without the consent of your doctor. Avoid contact with people who have recently received live vaccines (such as flu vaccine inhaled through the nose). To lower the chance of getting cut, bruised, or injured, use caution with sharp objects like razors and nail cutters, and avoid activities such as contact sports. This drug may make you dizzy. Alcohol or marijuana can make you more dizzy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Avoid alcoholic beverages. Talk to your doctor if you are using marijuana. Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products). Children may be more sensitive to the side effects of this drug, especially mental/mood changes (such as severe depression, thoughts/attempts of suicide). Peginterferon may also slow down a child's growth. Normal weight gain and growth usually return after treatment is over, but the final adult height may be lower than expected. See the doctor regularly so your child's height and weight can be checked. Peginterferon alfa-2a is not recommended for use during pregnancy. It may harm an unborn baby. Consult your doctor for more details and to discuss reliable forms of birth control. Peginterferon alfa-2a, when used in combination with ribavirin, must not be used during pregnancy by either the pregnant woman or her male partner. The combination may harm an unborn baby. Two reliable forms of birth control (such as condoms, birth control pills) must be used whenever at least one sexual partner is using these medicines together, and for at least 6 months after stopping treatment. If you or your partner become pregnant, or if you think you or your partner may be pregnant, tell your doctor right away. It is unknown if this drug passes into breast milk. Consult your doctor before breast-feeding.

DRUG INTERACTIONS: Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval. A product that may interact with this drug is: telbivudine.

OVERDOSE: If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center.