In the U.S.—

• Biological response modifier
• Immunomodulator

Gamma interferon (GAM-a in-ter-FEER-on) is a synthetic (man-made) version of a substance naturally produced by cells in the body to help fight infections and tumors. Gamma interferon is used to treat chronic granulomatous disease and osteopetrosis.

Gamma interferon is available only with your doctor's prescription, in the following dosage form:

Parenteral
• Injection (U.S.)

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For gamma interferon, the following should be considered:

Allergies—Tell your doctor if you have ever had any unusual or allergic reaction to gamma interferon.

Pregnancy—Gamma interferon has not been studied in pregnant women. However, in monkeys given 100 times the human dose of gamma interferon and in mice, there was an increase in deaths of the fetus. Also, in mice, toxic doses of gamma interferon caused bleeding of the uterus.

Breast-feeding—It is not known whether gamma interferon passes into the breast milk. However, because this medicine may cause serious side effects, breast-feeding may not be recommended while you are receiving it. Discuss with your doctor whether or not you should breast-feed while you are receiving gamma interferon.

Children—Studies on this medicine have been done mostly in children and it is not expected to cause different side effects or problems than it does in adults.

Older adults—Many medicines have not been studied specifically in older people. Therefore, it may not be known whether they work exactly the same way they do in younger adults or if they cause different side effects or problems in older people. There is no specific information comparing use of gamma interferon in the elderly with use in other age groups.

Other medicines—Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. Tell your health care professional if you are taking any other prescription or nonprescription (over-the-counter [OTC]) medicine.

• Convulsions (seizures) or
• Mental problems (or history of)—Risk of problems affecting the central nervous system may be increased

• Heart disease or
• Multiple sclerosis or
• Systemic lupus erythematosus—May be worsened by gamma interferon

If you are injecting this medicine yourself, use it exactly as directed by your doctor. Do not use more or less of it, and do not use it more often than your doctor ordered. The exact amount of medicine you need has been carefully worked out. Using too much will increase the risk of side effects, while using too little may not improve your condition.

Each package of gamma interferon contains a patient instruction sheet. Read this sheet carefully and make sure you understand:

• How to prepare the injection.
• Proper use of disposable syringes.
• How to give the injection.
• How long the injection is stable.

If you have any questions about any of this, check with your health care professional.

While you are using gamma interferon, your doctor may want you to drink extra fluids. This will help prevent low blood pressure due to loss of too much water.

Gamma interferon often causes flu-like symptoms, which can be severe. This effect is less likely to cause problems if you inject your gamma interferon at bedtime.

Dosing—

The dose of gamma interferon will be different for different patients. The dose that is used may depend on a number of things, including the patient's body size. If you are receiving gamma interferon at home, follow your doctor's orders or the directions on the label. If you have any questions about the proper dose of gamma interferon, ask your doctor.

Missed dose—

If you miss a dose of this medicine, do not give the missed dose at all and do not double the next one. Check with your doctor for further instructions.

Storage—

To store this medicine:

• Keep out of the reach of children.
• Store in the refrigerator.
• Keep the medicine from freezing.
• Discard any unopened vials that are left at room temperature for more than 12 hours.
• Do not keep outdated medicine or medicine no longer needed. Ask your health care professional how you should dispose of any medicine you do not use. Be sure that any discarded medicine is out of the reach of children.

It is very important that your doctor check your progress at regular visits to make sure that this medicine is working properly and to check for unwanted effects.

This medicine commonly causes a flu-like reaction, with aching muscles, fever and chills, and headache. To prevent problems from your temperature going too high, your doctor may ask you to take acetaminophen before each dose of gamma interferon. You may also need to take it after a dose to bring your temperature down. Follow your doctor's instructions carefully about taking your temperature, and how much and when to take the acetaminophen.

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• Rare
  • Black, tarry stools;  blood in urine or stools;  confusion;  cough or hoarseness;  loss of balance control;  lower back or side pain;  mask-like face ;  painful or difficult urination;  pinpoint red spots on skin;  shuffling walk;  stiffness of arms or legs;  trembling and shaking of hands and fingers;  trouble in speaking or swallowing;  trouble in thinking or concentrating ;  trouble in walking;  unusual bleeding or bruising 
  
  

Other side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. However, check with your doctor if any of the following side effects continue or are bothersome:

• More common
  • Aching muscles;  diarrhea;  fever and chills;  general feeling of discomfort or illness;  headache;  nausea or vomiting;  skin rash;  unusual tiredness 
  
  

• Less common
  • Back pain;  dizziness;  joint pain;  loss of appetite;  weight loss 
  
  

Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor.