Dexamethasone is a glucocorticoid given orally, in the management of various disorders in which corticosteroids are indicated. Its lack of mineralocorticoid properties makes dexamethasone particularly suitable for treating cerebral oedema and congenital adrenal hyperplasia. It is also used in the differential diagnosis of Cushing’s syndrome.
Dexamethasone is readily absorbed from the gastro-intestinal tract. Its biological half-life in plasma is about 190 minutes. Binding of dexamethasone to plasma proteins is less than most other corticosteroids.
Dexamethasone is a glucocorticoid. 70µg of dexamethasone is equivalent in anti-inflammatory activity to about 5mg of prednisolone
It has been used, either in the form of the tree alcohol or in one of the esterified form, in the treatment of all conditions for which corticosteroid therapy is indicated, excerpt adrenal-deficiency states for which its lack of sodium-retaining properties make it less suitable than hydrocortisone with supplementary fludrocortisone. Its lack of mineralocorticoid properties makes dexamethasone particularly suitable for treating cerebral oedema and suppressing corticotrophin secretion in congenital adrenal hyperplasia.
For administration by mouth dexamethasone is used in usual intial doses of 0,5 to 9mg daily in divided doses. Dexamethasone is also used by mouth in the dexamethasone suppression tests for the diagnosis of Cushing’s syndrome
Muscle weakness, osteoporosis, fractures, Cushing’s syndrome, pituitary-adrenal axis suppression, growth suppression, glucose intolerance, acne, oedema, hypertension, hypokalaemia, alkalosis, cataracts, glaucoma, peptic ulcer, nausea, vomiting, headache, vertigo, seizures, psychosis, pseudotumor cerebri, skin atrophy.
Use with caution in patients with hypothyroidism, cirrhosis, hypertension, congestive heart failure, ulcerative colitis, thromboembolic disorders; fatalities have occurred due to adrenal insufficiency in asthmatic patients during and after transfer from systemic corticosteroids to aerosol steroids; during this period, aerosol steroids do not provide the systemic steroid needed to treat patients having trauma, surgery, or infections; may retard bone growth.
There is inadequate evidence of safety in human pregnancy and there may be a very small risk of cleft palate and intrauterine growth retardation in the fetus. There is evidence of harmful effect on pregnancy in animals.
Corticosteroids appear in breast milk and could suppress growth, interfere with endogenous corticosteroid production or cause other unwanted effects. Mothers taking pharmacological doses of corticosteroid should be advised not to nurse.
Dexamethasone is contraindicated in patients with active untreated infections, viral, fungal or tuberculous disease of the eyes.
As phenytoin, barbiturates, ephedrine and rifampicin may enhance the metabolic clearance of corticosteroids, resulting in decreased blood levels and reduced physiological activity, the dosage may have to be adjusted. These interactions may interfere with dexamethasone suppression tests which should be interpreted with caution during administration of these drugs.
The prothrombin time should be checked frequently in patients who are receiving corticosteroids and coumarin anticoagulants at the same time.