dexamethasone

dexamethasone /dex·a·meth·a·sone/ (dek″sah-meth´ah-sōn) a synthetic glucocorticoid used primarily as an antiinflammatory in various conditions, including collagen diseases and allergic states; it is the basis of a screening test in the diagnosis of Cushing's syndrome; used also as the acetate or sodium phosphate salt.

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dex·a·meth·a·sone (dks-mth-sn, -zn)

n.

A synthetic glucocorticoid used primarily in the treatment of inflammatory disorders.

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dexamethasone

[dek′səmeth′əsōn]

a long-acting synthetic adrenocorticoid with intense antiinflammatory activity and mineralocorticoid activity.

indications It is prescribed topically and systemically in the treatment of inflammatory conditions.

contraindications Systemic fungal infections or known hypersensitivity to this drug prohibits its use.

adverse effects Among the more serious adverse reactions are GI, endocrine, neurologic, fluid, and electrolyte disturbances.

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dexamethasone

a synthetic glucocorticoid used primarily as an anti-inflammatory agent in various conditions, including autoimmune diseases, hypersensitivity reactions and shock; it is also used in a screening test for the diagnosis of cushing's syndrome, and for the termination of pregnancy in cattle.

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dexamethasone suppression test

the determination of blood cortisol levels before and after administration of dexamethasone assists in diagnosing Cushing's syndrome and identifying the cause, depending on the protocol and dose used. Dexamethasone suppresses pituitary secretion of ACTH in normal animals and therefore the blood level of cortisol is decreased; low doses do not suppress cortisol levels in dogs with pituitary-dependent Cushing's syndrome, high doses do. Cortisol production by functional adrenal tumors is not affected by dexamethasone.

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antiinflammatory drug 

A drug which inhibits or suppresses most inflammatory responses of an allergic, bacterial, traumatic or anaphylactic origin, as well as being immunosuppressant. They include the corticosteroids (e.g. betamethasone, dexamethasone, fluorometholone, hydrocortisone acetate, loteprednol etabonate, prednisolone, rimexolone, triamcinolone). They are sometimes combined with an antibiotic drug (e.g. betamethasone combined with neomycin or sulfacetamide, dexamethasone combined with neomycin or polymyxin B). Corticosteroids have side effects, such as enhancing the activity of herpes simplex virus, fungal overgrowth, raising intraocular pressure or cataract formation.There are other antiinflammatory drugs that are non-steroidal (NSAID) and have little toxicity. They act mainly by blocking prostaglandin synthesis. These include diclofenac sodium, flurbiprofen sodium, indomethacin, ketorolac, nepafenac and oxyphenbutazone. See immunosuppressants; steroid.

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dexamethasone

Alti-Dexamethasone (CA), Decadron

Pharmacologic class: Glucocorticoid

Therapeutic class: Anti-inflammatory

Pregnancy risk category C

Action

Unclear. Reduces inflammation by suppressing polymorphonuclear leukocyte migration, reversing increased capillary permeability, and stabilizing leukocyte lysosomal membranes. Also suppresses immune response (by reducing lymphatic activity), stimulates bone marrow, and promotes protein, fat, and carbohydrate metabolism.

Availability

Elixir: 0.5 mg/5 ml

Oral solution: 0.5 mg/5 ml, 1 mg/ml

Solution for injection (sodium phosphate): 4 mg/ml, 10 mg/ml, 20 mg/ml, 24 mg/ml

Tablets: 0.25 mg, 0.5 mg, 0.75 mg, 1 mg, 1.5 mg, 2 mg, 4 mg, 6 mg

⊘Indications and dosages

➣ Allergic and inflammatory conditions

Adults: 0.75 to 9 mg/day (dexamethasone) P.O. as a single dose or in divided doses; in severe cases, much higher dosages may be needed. Dosage requirements vary and must be individualized based on disease and patient response.

➣ Cerebral edema

Adults: Initially, 10 mg (sodium phosphate) I.V., followed by 4 mg I.M. q 6 hours. Then reduce dosage gradually over 5 to 7 days.

➣ Suppression test for Cushing's syndrome

Adults: 1 mg P.O. at 11 P.M. or 0.5 mg P.O. q 6 hours for 48 hours (with urine collection testing, as ordered)

Off-label uses

• Acute altitude sickness
• Bacterial meningitis
• Bronchopulmonary dysplasia in preterm infants
• Hirsutism
• Suppression test for detection, diagnosis, or management of depression

Contraindications

• Hypersensitivity to drug, benzyl alcohol, bisulfites, EDTA, creatinine, polysorbate 80, or methylparaben
• Systemic fungal infections

Precautions

Use cautiously in:
• renal insufficiency, cirrhosis, diabetes mellitus, diverticulitis, GI disease, cardiovascular disease, hypoprothrombinemia, hypothyroidism, myasthenia gravis, glaucoma, osteoporosis, infections, underlying immunosuppression, psychotic tendencies
• pregnant or breastfeeding patients
• children.

Administration

• Give P.O. dose with food or milk.
• When giving I.M., inject deep into gluteal muscle; rotate sites as needed.
• For I.V. use, drug may be given undiluted as a single dose over 1 minute or added to dextrose or I.V. saline solutions and given as an intermittent infusion at prescribed rate.

Route	Onset	Peak	Duration
P.O.	Unknown	1-2 hr	2.75 days
I.V.	1 hr	1 hr	Variable
I.M. (sodium phosphate)	1 hr	1 hr	6 days

Adverse reactions

CNS: headache, malaise, vertigo, psychiatric disturbances, increased intracranial pressure, seizures

CV: hypotension, thrombophlebitis, myocardial rupture after recent myocardial infarction, thromboembolism

EENT: cataracts

GI: nausea, vomiting, abdominal distention, dry mouth, anorexia, peptic ulcer, bowel perforation, pancreatitis, ulcerative esophagitis

Metabolic: decreased carbohydrate tolerance, hyperglycemia, cushingoid appearance (moon face, buffalo hump), decreased growth (in children), latent diabetes mellitus, sodium and fluid retention, negative nitrogen balance, adrenal suppression, hypokalemic alkalosis

Musculoskeletal: muscle wasting, muscle pain, osteoporosis, aseptic joint necrosis, tendon rupture, long bone fractures

Skin: diaphoresis, angioedema, erythema, rash, pruritus, urticaria, contact dermatitis, acne, decreased wound healing, bruising, skin fragility, petechiae

Other: facial edema, weight gain or loss, increased susceptibility to infection, hypersensitivity reactions

Interactions

Drug-drug. Barbiturates, phenytoin, rifampin: decreased dexamethasone effects

Digoxin: increased risk of digoxin toxicity

Ephedrine: increased dexamethasone clearance

Estrogen, hormonal contraceptives: blocking of dexamethasone metabolism

Fluoroquinolones: increased risk of tendon rupture

Itraconazole, ketoconazole: increased dexamethasone blood level and effects

Live-virus vaccines: decreased antibody response to vaccine, increased risk of adverse reactions

Loop and thiazide diuretics: additive hypokalemia

Nonsteroidal anti-inflammatory drugs: increased risk of GI adverse effects

Somatrem, somatropin: decreased response to these drugs

Drug-diagnostic tests. Calcium, potassium: decreased levels

Cholesterol, glucose: increased levels

Nitroblue tetrazolium test: false-negative result

Drug-herbs. Echinacea: increased immune-stimulating effect

Ginseng: potentiation of immune-modulating response

Drug-behaviors. Alcohol use: increased risk of gastric irritation and GI ulcers

Patient monitoring

• Monitor blood glucose level closely in diabetic patients receiving drug orally.
• Monitor hemoglobin and potassium levels.
• Assess for occult blood loss.
☞ In long-term therapy, never discontinue drug abruptly. Dosage must be tapered gradually.

Patient teaching

☞ Instruct patient to immediately report sudden weight gain, swelling of face or limbs, excessive nervousness or sleep disturbances, excessive body hair growth, vision changes, difficulty breathing, muscle weakness, persistent abdominal pain, or change in stool color.
• Tell patient to take oral drug with or after meals.
• Advise patient to report vision changes.
• Inform patient that drug makes him more susceptible to infection. Advise him to avoid crowds and exposure to illness.
☞ Caution patient not to stop taking drug abruptly.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, herbs, and behaviors mentioned above.