Etanercept

Etanercept belongs to the class of biological response modifiers called tumour necrosis factor (TNF) blockers. It is the first drug of its kind to be approved for the treatment of psoriatic arthritis. Other indications include treatment of rheumatoid arthritis and polyarticular-course juvenile rheumatoid arthritis. It is also proving useful in the treatment of psoriasis. Clinical trials have shown that it is well tolerated and significantly improves psoriatic target lesions.

How does it work?

Etanercept is genetically engineered from human protein. It works by directly binding to TNF molecules in the blood and diseased tissue. Etanercept-bound TNF cannot bind to or activate TNF receptors, which is the primary cause of the inflammation, redness, itching and flaky skin patches characteristic of psoriasis.

How is it given?

Etanercept is given by subcutaneous injection twice weekly. After initial counselling and training by a doctor on how to prepare and inject the drug, patients can usually self-administer at home. Injections are usually into the thigh, stomach or upper arm. A different site should be used at each injection to reduce soreness and prevent the skin from becoming tender, red, bruised or hard. Regular follow up visits to the doctor is necessary whilst on etanercept.

The recommended dose for treating psoriatic arthritis is 25mg twice weekly. This can be give alone or in combination with methotrexate.

Precautions

Because etanercept works by selectively targeting only those chemicals involved in causing psoriatic arthritis or psoriasis, theoretically it should not have an effect on the rest of the body's immune system. Even so caution must be taken when considering its use in patients prone to infections or in those with chronic or recurrent infections. It should not be used in patients with sepsis or active infections.

The incidence of etanercept-associated cases of tuberculosis (TB) is lower than that seen with infliximab, hence TB screening before starting etanercept is not required by the FDA. However, current practice is to perform tuberculin skin testing for both drugs before commencing treatment.

Side Effects

Etanercept appears to be very well tolerated. Mild to moderate injection site reactions (redness, swelling, itching, pain) appear to be the most common side effect. These tend to occur in the first month and then become less frequent. Cool compresses and 1% hydrocortisone ointment may help to alleviate the discomfort.

If any of the following symptoms or signs are severe or do not go away you should contact your doctor.

• Coughing, wheezing or chest pain
• Nausea and/or vomiting
• Stomach pain
• Fever, headache, chills or other signs of infection
• Hot, red, swollen area on the skin or bruising
• Sore eyes (uveitis has been described as a possible uncommon adverse reaction to etanercept).

Severe cutaneous reactions have rarely been reported, including Stevens Johnson syndrome and toxic epidermal necrolysis.