Most glucocorticoids are synthetic analogues of hormones secret-ed by the adrenal cortex. They exert anti-inflammatory, metabolic, and immunosuppressant effects. Drugs in this class include:
Glucocorticoids are well absorbed when administered orally. After I.M. administration, they’re absorbed completely.
Glucocorticoids are bound to plasma proteins and distributed through the blood.
Glucocorticoids are metabolized in the liver and excreted by the kidneys.
Glucocorticoids suppress hypersensitivity and immune responses through a process that isn’t entirely understood. Researchers be-lieve that glucocorticoids inhibit immune responses by:
§ suppressing or preventing cell-mediated immune reactions
§ reducing levels of leukocytes, monocytes, and eosinophils
§ decreasing the binding of immunoglobulins to cell surface re-ceptors
§ inhibiting interleukin synthesis.
Glucocorticoids suppress the redness, edema, heat, and tender-ness associated with the inflammatory response. They start on the cellular level by stabilizing the lysosomal membrane (a structurewithin the cell that contains digestive enzymes) so that it doesn’t release its store of hydrolytic enzymes into the cells.
As corticosteroids, glucocorticoids prevent the leakage of plasma from capillaries, suppress the migration of polymorphonuclear leukocytes (cells that kill and digest microorganisms), and inhibit phagocytosis (ingestion and destruction).
To ensure a job well done, glucocorticoids decrease antibody formation in injured or infected tissues and disrupt histamine syn-thesis, fibroblast development, collagen deposition, capillary dila-tion, and capillary permeability. (See How methylprednisoloneworks.)
Besides their use as replacement therapy for patients with adreno-cortical insufficiency, glucocorticoids are prescribed for immuno-suppression and reduction of inflammation and for their effects on the blood and lymphatic systems.
Many drugs interact with corticosteroids:
§ Aminoglutethimide, barbiturates, phenytoin, and rifampin may reduce the effects of corticosteroids.
§ Their potassium-wasting effects may be enhanced by ampho-tericin B, chlorthalidone, ethacrynic acid, furosemide, and thi-azide diuretics.
§ Erythromycin and troleandomycin may increase their effects by reducing their metabolism.
§ They reduce the serum concentration and effects of salicylates.
§ The risk of peptic ulcers associated with nonsteroidal anti-inflammatory drugs and salicylates increases when these agents are taken with corticosteroids.
§ The response to vaccines and toxoids may be reduced in a pa-tient taking corticosteroids.
§ Estrogen and hormonal contraceptives that contain estrogen in-crease the effects of corticosteroids.
§ The effects of antidiabetic drugs may be reduced, resulting in in-creased blood glucose levels. (See Adverse reactions to cortico-steroids.)