Corticosteroids are highly plasma protein bound (around 90%). Binding may be both "generic" (to albumin) and "specific". Specific binding occurs to corticotrophin binding globulin (CBG), which has a high affinity but low capacity and hence binds endogenous corticosteroids only. Albumin binds both endogenous and synthetic steroids.
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Corticosteroids have a short half-life, with that of cortisol being only 90 minutes. The drugs are metabolised in the liver, where the C4-5 double bind is reduced and conjugation with sulphate or glucuronic acid occurs. They are then excreted in the urine. Cortisone and prednisone are inactive prodrugs; upon liver metabolism they are converted to hydrocortisone and prednisolone respectively.