Dexamethasone is a type of corticosteroid medication. It is used in the treatment of many conditions, including rheumatic problems, a number of skin diseases, severe allergies, asthma, chronic obstructive lung disease, croup, brain swelling, and along with antibiotics in tuberculosis. In adrenocortical insufficiency, it should be used together with a medication that has greater mineralocorticoid effects such as fludrocortisone. In preterm labor, it may be used to improve outcomes in the baby. It may be taken by mouth, as an injection into a muscle, or intravenously. The effects of dexamethasone are frequently seen within a day and last for about three days.
Mechanism of Action of Dexamethasone
Dexamethasone is a glucocorticoid agonist. Unbound dexamethasone crosses cell membranes and binds with high affinity to specific cytoplasmic glucocorticoid receptors. This complex binds to DNA elements (glucocorticoid response elements) which results in a modification of transcription and, hence, protein synthesis in order to achieve inhibition of leukocyte infiltration at the site of inflammation, interference in the function of mediators of inflammatory response, suppression of humoral immune responses, and reduction in edema or scar tissue. The antiinflammatory actions of dexamethasone are thought to involve phospholipase A2 inhibitory proteins, lipocortins, which control the biosynthesis of potent mediators of inflammation such as prostaglandins and leukotrienes.
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Glucocorticoids are capable of suppressing the inflammatory process through numerous pathways. They interact with specific intracellular receptor proteins in target tissues to alter the expression of corticosteroid-responsive genes. Glucocorticoid-specific receptors in the cell cytoplasm bind with steroid ligands to form hormone-receptor complexes that eventually translocate to the cell nucleus. There these complexes bind to specific DNA sequences and alter their expression. The complexes may induce the transcription of mRNA leading to the synthesis of new proteins. Such proteins include lipocortin, a protein known to inhibit PLA2a and thereby block the synthesis of prostaglandins, leukotrienes, and PAF. Glucocorticoids also inhibit the production of other mediators including AA metabolites such as COX, cytokines, the interleukins, adhesion molecules, and enzymes such as collagenase.
Indications of Dexamethasone
- Injection – for the treatment of endocrine disorders, rheumatic D=disorders, collagen diseases, dermatologic diseases, allergic states, ophthalmic diseases, gastrointestinal diseases, respiratory diseases, hematologic disorders, neoplastic diseases, edematous states, cerebral edema.
- Ophthalmic ointment and solution – for the treatment of steroid responsive inflammatory conditions of the palpebral and bulbar conjunctiva, cornea, and anterior segment of the globe.
- The ophthalmic solution only – for the treatment of steroid responsive inflammatory conditions of the external auditory meatus
- Topic cream – for the relief of the inflammatory and pruritic manifestations of corticosteroid-responsive dermatoses
- Oral aerosol – for the treatment of bronchial asthma and related corticosteroid-responsive bronchospastic states intractable to an adequate trial of conventional therapy
- Intranasal aerosol – for the treatment of allergic or inflammatory nasal conditions, and nasal polyps
- Endocrine disorders – Endocrine exophthalmos.
- Non-endocrine disorders – Dexamethasone may be used in the treatment of non-endocrine corticosteroid-responsive conditions including Allergy and anaphylaxis: Anaphylaxis. Arteritis collagenosis: Polymyalgia rheumatica, polyarteritis nodosa.
- Hematological disorders – Haemolytic anaemia (also auto immune), leukaemia, myeloma, idiopathic thrombocytopenic purpura in adults,reticulolymphoproliferative disorders (see also under oncological disorders).
- Gastroenterological disorders – For treatment during the critical stage in ulcerative colitis (rectal only); regional enteritis (Crohn’s disease), certain forms of hepatitis.
- Muscular disorders Polymyositis.
- Neurological disorders – Raised intra-cranial pressure secondary to cerebral tumors, acute exacerbations of multiple sclerosis.
- Ocular disorders – Anterior and posterior uveitis, optic neuritis, chorioretinitis, iridocyclitis, temporal arteritis, orbital pseudotumour.
- Renal disorders – Nephrotic syndrome.
- Pulmonary disorders – Chronic bronchial asthma, aspiration pneumonitis, chronic obstructive pulmonary disease (COPD), sarcoidosis, allergic pulmonary disease such as farmer’s and pigeon breeder’s lung, LÖffler’s syndrome, cryptogenic fibrosing alveolitis.
- Rheumatic disorders – some cases or specific forms (Felty’s syndrome, SjÖrgen’s syndrome) of rheumatoid arthritis, including juvenile rheumatoid arthritis, acute rheumatism, lupus erythematosus disseminatus, temporal arteritis (polymyalgia rheumatica).
- Skin disorders – Pemphigus Vulgaris, bullous pemphigoid, erythrodermas, serious forms of erythema multiforme (Stevens-Johnson syndrome), mycosis fungoides, bullous dermatitis herpetiformis.
- Oncological Disorders – lymphatic leukemia,
………This drug must be avoided due to it major side effect
References
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