Erythroblastopenia

Definition

Dexamethasone is a synthetic glucocorticoid. Its naturally occuring counterparts are hydrocortisone and cortisone. Although the drug is used in a variety of ways, in general, it reduces inflammation and depresses the immune system. Dexamethasone may also be called by its brand name, Decadron.

Purpose

Dexamethasone is used in the treatment of many disorders. For example, it may be used:

• as replacement therapy in the treatment of Addison's disease

• in the management of various inflammatory disorders, such as rheumatoid arthritis

• in managing allergic disorders, such as asthma

Patients with ulcerative colitis may benefit from dexamethasone therapy, as might those with exacerbations of multiple sclerosis. Blood disorders, such as thrombocytopenic purpura or erythroblastopenia, may also be managed with dexamethasone.

Dexamethasone is often prescribed to patients with cancer. In some cases, the drug is part of the drug treatment for the disease, and in other cases it is used to manage side effects caused by the treatment or the cancer itself.

Dexamethasone may be used to decrease abnormally high levels of potassium that develop in association with cancer. In some cases, it may be used as palliation in leukemia or lymphoma. Because of its antiinflammatory properties, dexamethasone may help reduce swelling in the brain caused by a brain tumor. It may also help prevent hypersensitivity reactions associated with drugs like paclitaxel. Dexamethasone is also commonly used to treat nausea associated with chemotherapy. It is particularly useful with the drug cisplatin, which frequently causes nausea and vomiting.

In non-Hodgkin's lymphoma (NHL), dexamethasone is part of a drug regimen known as "DHAP." Here, dexamethasone is given with chemotherapy drugs called cisplatin and cytarabine. Also in treating NHL, dexamethasone may be used in a regimen caled "m-BACOD," which also includes the administration of methotrexate, leucovorin, bleomycin, doxorubicin, cyclophosphamide, and vincristine. Dexamethasone may also be helpful in patients with multiple myeloma. In the "EDAP" regimen, dexamethasone is given with etoposide, cytosine arabinoside (cytarabine), and cisplatin; in VAD, it is given with vincristine and doxorubicin.

Description

Patients should not stop taking dexamethasone without first consulting their physician. When dexamethasone treatment stops, it must be gradually reduced over time before it can be completely discontinued. Sudden withdrawal of glucocorticoids may result in adrenal insufficiency.

When possible, the drug should be taken before nine A.M. to imitate the time that the body's corticosteroid levels are typically at their highest. A child taking dexamethasone will be carefully monitored to ensure the drug is not affecting his or her growth. Patients taking large doses of dexamethasone should try to take the drug with meals. Antacids may be recommended between meals to reduce gastrointestinal effects and to prevent peptic ulcer.

Recommended dosage

Dexamethasone is available in oral, intravenous (IV), topical, ophthalmic, or inhaled form. In cancer patients, the oral and IV routes are used most frequently. The pill is available in several color-coded dosages [0.25 milligrams (mg), 0.5mg, 0.75mg, 1.5mg, 4mg, and 6mg]. Dexamethasone should be given very slowly by the IV route.

Dosages to treat disease are highly individualized, but generally start at 0.75 to 9.0 mg per day. The lowest therapeutic dose should be given, though amounts given may need to be increased during times of stress. Dosages of medications may be changed based on factors specific to the individual. The following dosages are general guidelines for dexamethasone when it is used in conjunction with chemotherapy agents:

• DHAP. Forty milligrams of dexamethasone is given in pill or IV form per day for the first four days of treatment, followed by cisplatin and cytarabine.

• M-BACOD. Six milligrams per meter square (mg/m2) of dexamethasone is given as a pill on the first five days of treatment.

• EDAP. Forty milligrams of dexamethasone is given in pill form on the first four days of treatment. It is given again on days 9-12, and 17-20.

When used to prevent or manage nausea or vomiting associated with chemotherapy, dexamethasone is given in the following dosages: 4-20 mg IV every 4-6 hours. Alternatively, a one-time dose of 10-20 mg may be given IV. When pills are preferred, 4-8 mg of dexamethasone may be given four times, every four hours. When used to prevent hypersensitivity reactions in paclitaxel treatment, 20mg should be given orally twelve and six hours before treatment begins.

Precautions

Dexamethasone should be used cautiously in patients with kidney or liver problems, hypothyroidism, high blood pressure, or a history of heart attack. Patients with diabetes mellitus should monitor blood sugar levels carefully, as hyperglycemia may result. If changes occur, patients should notify their doctors immediately. Sudden cessation of dexamethasone therapy is dangerous for patients on therapy for longer than two weeks. The drug should be gradually withdrawn under a physician's guidance.

Side effects

Adverse effects vary widely, and depend on the dosage and route of the drug. Certain drugs may result in decreased blood levels, and therefore render dexamethasone less effective. Patients taking the following drugs should be carefully monitored for decreased levels of dexamethasone: phenytoin, phenobarbitol, ephedrine, and rifampin. Conversely, some drugs, such as troleandomycin, may increase blood levels of dexamethasone.

Because of its immunosuppressive properties, dexamethasone may decrease the signs and symptoms of infection. Depending on the amount of drug being administered, patients may consider taking measure to prevent infection by avoiding crowded areas and washing their hands frequently. Patients should inform their doctor if they notice a fever, sore throat, or cuts or abrasions that don't heal. Laboratory tests may also be affected-false negative results may occur in the nitroblu-tetrazolium test for bacterial infections.

Glucocorticoids, such as hydrocortisone, tend to make the body retain salt. Although dexamethasone's salt-retaining properties are not as severe as hydrocortisone's, salt retention may result in fluid and electrolyte imbalances. Patients at risk may experience high blood pressure or even congestive heart failure. Weight gain or swelling may indicate salt and fluid retention.

Other adverse effects may include headache, dizziness, insomnia, increased appetite, mood swings, menstrual changes, muscle weakness, acne and/or sweating. Depression may be worsened with dexamethasone use. Some men experience changes in the motility and number of their sperm with steroid treatment. Patients should talk to their doctors about any unusual symptoms they experience. In cancer patients, increased appetite may actually be beneficial.

Dexamethasone crosses the placenta and is excreted in breast milk. If a pregnant woman is taking large doses of the drug, her newborn should be monitored for evidence of hypoadrenalism. Optimally, breast-feeding should be avoided. There is some concern that dexamethasone, in large quantities, suppresses growth or disrupts the baby's normal corticosteroid production.

Interactions

Patients should discuss all their medications, prescription and non-prescription, with their doctor. If dexamethasone is administered in amounts that suppress the immune system, live vaccines, such as small pox, should not be administered. Dexamethasone may alter the effect of anticoagulant drugs. Frequent laboratory tests should be performed to monitor blood levels. If dexamethasone is given with diuretics, potassium levels may be abnormally low, and should be frequently monotired. Doctors may recommend that patients on long-term therapy follow a potassium-rich diet.

KEY TERMS

Addison's disease

A potentially life-threatening condition that results when adrenocortical function fails. Hypoadrenalism.

Glucocorticoid

An adrenocortical steroid hormone that is stimulated by the anterior pituitary. The three naturally occuring types are hydrocortisone, corticosterone, and cortisone.

Hyperglycemia

An abnormally increased level of glucose (sugar) in the blood.

Palliation

Therapy aimed at relieving symptoms and promoting comfort, but not producing a cure.