Comparative properties steroids
Steroids used therapeutically will have differential properties to each other that can be very important to understand. Some of these differences may have minimal clinical impact but others such as the relative potency and insolubility designed into some esters are very important. Most steroids used at long term therapeutic dosage (not replacement physiological dosage which in adults is about 30mg of hydrocortisone a day) have predictable side effects that do not vary much.
|Steroid||Comparative glucocorticoid activity||Comparative mineralocorticoid activity||Comment|
|Prednisolone||5mg||16mg||The active drug that prednisone is metabolised to|
|Prednisone||5mg||16mg||Prodrug with ketone radical on C-11 which is hydrolysed to prednisolone.|
|Dexamethasone||750 µg||none||Usual to use to treat CNS oedema and if heart failure. The doses of the various salts cause confusion and be careful of the preparation used if given into an sensory organ or CSF as it must be preservative free|
|Hydrocortisone (cortisol)||20mg||20mg||Corticosteroid of choice for physiological replacement as fair mineralocorticoid activity|
|Methylprednisolone||4mg||10mg||Prodrug with ketone radical on C-11 which is hydrolysed.|
|Cortisone acetate||25mg||25mg||Prodrug with ketone radical on C-11 which is hydrolysed. As acetate will be insoluble. Fair mineralocorticoid activity.|
|Deflazacort||6mg||No affinity for corticosteroid binding globulin (transcortin) and has markedly less crossing of the blood-brain barrier|
|Fludrocortisonealdosterone||2mg||160µg||Additional fluorination at the C-9 position enhances both glucocorticoid and mineralocorticoid activity|
The introduction to the hydrocortisone basic structure of a double bond between C-1 and C-2 increases glucocorticoid and anti-inflammatory activity. Many steroids are administered as esters. Esterification of the alcohol at C-21 determines the extent of water/lipid solubility. Esterification with acetic acid, yields water-insoluble drugs used for long acting IM or IA formulations (eg, methylprednisolone acetate). Esterification by succinic acid or a phosphate can yield a hydrosoluble ester useful for iv preparations. Esterification at C-17 (valerate) produces a lipophilic compound with an enhanced topical:systemic potency ratio. Similarly fluticasone propionate is designed to be rapidly metabolised to reduce systematic side effects and is used in respiratory inhalers.