BMA Concise Guide to Medicine & Drugs

Interferon

Brand names Avonex, Betaferon, Extavia, Immukin, IntronA, Pegasys, Peglntron, Rebif, Roferon-A, Viraferon, ViraferonPeg

Used in the following combined preparations None

QUICK REFERENCE

Drug group Antiviral drug and anticancer drug

Overdose danger rating Medium

Dependence rating Low

Prescription needed Yes

Available as generic No

GENERAL INFORMATION

Interferons are a group of substances normally produced in human and animal cells that have been infected with viruses or stimulated by other substances. They are thought to promote resistance to several types of viral infection. Three main types of interferon (alpha, beta, and gamma) are used to treat a range of diseases. Interferon alpha is used for leukaemias, other cancers, and chronic hepatitis B and C. Interferon beta reduces the frequency and severity of relapses in multiple sclerosis. Interferon gamma is prescribed in conjunction with antibiotics for patients suffering from chronic granulomatous disease or from severe malignant osteopetrosis (a rare inherited condition in which the bones become abnormally dense).

Interferons can cause severe adverse effects.

INFORMATION FOR USERS

This drug is given only under medical supervision and is not for self-administration.

How taken/used Injection.

Frequency and timing of doses Once daily 3 times a week, depending on product and condition being treated.

Adult dosage range Depends on product and condition being treated. Dosage may sometimes be calculated from body surface area.

Onset of effect Active inside the body within 1 hour, but effects may not be noted for 1–2 months.

Duration of action Immediate effects last for about 12 hours.

Diet advice None.

Storage Store in a refrigerator at 2–8°C. Do not let it freeze, and protect from light. Keep out of the reach of children.

Missed dose Not applicable. This drug is usually given only in hospital under close medical supervision.

Stopping the drug Discuss with your doctor.

Exceeding the dose Overdosage is unlikely since treatment is carefully monitored.

POSSIBLE ADVERSE EFFECTS

Headache, lethargy, depression, dizziness, drowsiness, digestive disturbances, chills, fever, muscle aches, poor appetite, and weight loss are common adverse effects of interferon. Hair loss and vision problems are rarer side effects. Notify your doctor of all unusual symptoms without delay; some may be dose-related, requiring a reduction in dosage.

INTERACTIONS

General note A number of drugs increase the risk of adverse effects on the blood, heart, or nervous system. This is taken into account when prescribing an interferon with other drugs.

Vaccines Interferon may reduce the effectiveness of vaccines.

Theophylline/aminophylline The effects of this drug may be increased by interferon.

Sedatives All drugs that have a sedative effect on the central nervous system are likely to increase the sedative properties of interferon. Such drugs include opioid analgesics, anti-anxiety and sleeping drugs, antihistamines, antidepressants, and antipsychotics.

SPECIAL PRECAUTIONS

Interferon is prescribed only under close medical supervision, taking account of your present condition and medical history. However, be sure to tell your doctor if:

· You have long-term liver or kidney problems.

· You have heart disease.

· You have very abnormal blood lipid levels.

· You have had epileptic seizures.

· You have had any previous drug allergies.

· You have diabetes.

· You have had asthma, eczema, or psoriasis.

· You suffer from depression.

· You are taking other medicines.

Pregnancy Not usually prescribed. Safety in pregnancy not established. Discuss with your doctor.

Breast-feeding It is not known whether the drug passes into the breast milk. Discuss with your doctor.

Infants and children Not usually used.

Over 60 Increased likelihood of adverse effects. Reduced dose may be necessary.

Driving and hazardous work Not applicable.

Alcohol Avoid. Alcohol may increase the sedative effects of this drug.

PROLONGED USE

There may be an increased risk of liver damage. Blood cell production in the bone marrow may be reduced. Repeated large doses are associated with lethargy, fatigue, collapse, and coma.

Monitoring Frequent blood tests are required to monitor blood composition and liver function.