Source: Υπουργείο Υγείας (CY) Revision Year: 2017 Publisher: Medochemie Ltd, 1-10 Constantinoupoleos street, 3011, Limassol, Cyprus
Pharmacotherapeutic group: Corticosteroids for systemic use, plain, Glucocorticoids
ATC Code: H02AB02
Dexamethasone is a synthetic glucocorticoid with an anti-inflammatory potency about seven fold that of prednisolone. As with other glucocorticoids, dexamethasone also possesses anti-allergic, antipyretic and immunosuppressive properties.
It acts on the HPA at specific receptors on the plasma membrane. It diffuses across cell membranes in other tissues and following complexation with specific cytoplasmic receptors, enters the cell nucleus and stimulates protein synthesis.
It has practically no water and salt retaining properties, making it useful in patients with cardiac failure or hypertension. The long biological half life (36h – 54h) makes it suitable for use in conditions where continuous glucocorticoid action is wanted.
Generally corticosteroids are well absorbed from the gastro-intestinal tract. Following administration of dexamethasone sodium phosphate, it is rapidly hydrolysed to dexamethasone. Reported plasma half life is 190 minutes in adults. Intravenous administration gives a rapid onset of action of comparatively short duration. Intramuscular administration results in a slower onset of action with a comparatively longer duration. For this reason the intravenous route is the route of choice in initial dosage in life threatening situations, with maintenance being more appropriate by intramuscular administration.
Corticosteroids are rapidly distributed to all body tissues, they cross the placenta and are excreted in small quantities in breast milk. In the circulation it is extensively bound to plasma proteins, the majority to globulin (high affinity, low capacity) and less so to albumin (low affinity, high capacity). The plasma binding is proportionate to the dose, and in very high doses the majority is unbound. In hypoalbuminaemia the proportion of unbound dexamethasone increases.
Metabolism is mainly in the liver, but also in the kidney, excretion is mainly in urine as unconjugated steroids. Impaired renal function does not significantly influence the elimination of dexamethasone, whereas impaired hepatic function will prolong the elimination half life in severe impairment.
Not applicable.
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