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Brand Name, Dosage Format and Strength
Drenex 3 mg Tablet
Corticosteroid, Recombinant Growth Hormone
Dexamethasone is a highly potent and long-acting glucocorticoid whose main pharmacological actions include: (a) general effects on metabolism, water and electrolyte imbalance; (b) negative feedback effect on the hypothalamus and pituitary; (c) anti-inflammatory and immunosuppressive effects.
It has negligible sodium-retaining properties and has powerful anti-inflammatory and immunosuppressive effects.
Dexamethasone is well absorbed orally. Peak plasma levels are reached between 1 to 2 hrs after ingestion. The AUC, Vd, plasma clearance, and maximum plasma concentration are not dose-dependent but vary by a factor of about 0.6-0.7 after oral doses of 0.5-1.5 mg. The systemic bioavailability of dexamethasone is approximately 90% and the mean plasma t1/2 is 3.6 ± 0.9 hr.
Dexamethasone`s plasma t1/2 is shortened in CRF and simultaneous use of other drugs, e.g., rifampicin, phenobarbital, and phenytoin. Phenytoin decreases the oral bioavailability of dexamethasone by over 50%; plasma t1/2 is shortened and mean plasma clearance is increased to approximately three times the normal.
Metabolic clearance is reduced and plasma t1/2 is prolonged in patients with liver disease. Dexamethasone is cleared more rapidly from the circulation of the fetus and neonate than in the mother.
Up to 77% of dexamethasone is bound to plasma proteins. Percentage binding of dexamethasone, unlike that of cortisol, remains practically unchanged with increasing steroid concentrations.
Dexamethasone`s metabolism in the liver is slow and limited and 60% of the administered dose is excreted in the urine within 24 hrs largely as unconjugated steroids.