Mental health problems and suicide. INTRON A may cause patients to develop mood or behavioral problems. These can include irritability (getting easily upset) and depression (feeling low, feeling bad about yourself, or feeling hopeless). Some patients may have aggressive behavior. Former drug addicts may fall back into drug addiction or overdose. Some patients think about hurting or killing themselves or other people. Some patients have killed themselves (suicide) or hurt themselves or others. You must tell your healthcare provider if you are being treated for a mental illness or had treatment in the past for any mental illness, including depression and suicidal behavior. You should also tell your healthcare provider if you have ever been addicted to drugs or alcohol.

Eye problems. Changes in vision such as a decrease or loss of vision (blindness) may happen in some patients. You should have an eye exam before you take INTRON A. If you have eye problems or have had them in the past, you may need eye exams while you are taking INTRON A. Tell your healthcare provider or eye doctor right away if you have changes in your vision while taking INTRON A.

Heart problems. Some patients taking INTRON A may develop problems with their heart, including low blood pressure, fast heart rate, and very rarely, heart attacks. Tell your healthcare provider if you have had any heart problems in the past.

Blood problems. INTRON A commonly lowers two types of blood cells (white blood cells and platelets). In some patients, these blood counts may fall to dangerously low levels. If your blood cell counts become very low, you could get infections or have bleeding problems.

If you are taking INTRON A and REBETOL combination therapy, REBETOL can cause a drop in your number of red blood cells (anemia). A very low red blood cell count can be dangerous, especially if you have heart or breathing problems.

For other possible side effects of INTRON A, see "What are the possible side effects of INTRON A?" in this Medication Guide.

Body organ problems. INTRON A may cause lung problems including: trouble breathing, pneumonia, inflammation of lung tissue, and new or worse high blood pressure of the lungs (pulmonary hypertension), which can be severe and may in some cases lead to death. Certain symptoms like severe stomach pain may mean that your internal organs are being damaged. Cases of weakness, loss of coordination, and numbness due to stroke have been reported in patients taking Intron A, including patients with few or no reported risk factors for stroke.

What is INTRON® A?

The INTRON A product contains a man-made protein called interferon. Interferon is a protein that is part of the body's immune system that "interferes" with the growth of viruses or cancer cells.

It is not known if INTRON A or INTRON A/REBETOL® combination therapy can cure hepatitis B or C (permanently eliminate the virus) or if it can prevent liver failure or liver cancer that is caused by hepatitis B or C infection.

It is also not known if INTRON A or INTRON A/REBETOL combination therapy will prevent one infected person from infecting another person with hepatitis B or C.

Who should not take INTRON® A?

Do not take INTRON A alone or in combination with REBETOL® if y