Important Differences Between Synthetic and Natural Glucocorticoids

There are several important differences between synthetic and naturally occurring glucocorticoids. Glucocorticoids comprise one of the two major groups of corticosteroids produced by the human body. The 2^nd major group, mineralocorticoids, and glucocorticoids are both produced in the cortex of the adrenal glands.

Acting as hormones, glucocorticoids primarily affect metabolism, immune response and inflammation through out the body. The major natural glucocorticoid produced by the human body is cortisol. Importantly, naturally produced cortisol also has some mineralocorticoid properties which affect fluid and electrolyte balance.

The biologic activity profiles of many of the pharmacologic synthetic glucocorticoids also have some amount of mineralocorticoid properties. The ratio of glucocorticoid activity to mineralocorticoid activity varies between natural and synthetic glucocorticoids and also within the group of synthetic glucocorticoids.

Another key difference between synthetic and natural glucocorticoids is the degree of absorption through lipid barriers. When compared to a natural glucocorticoid such as cortisol, synthetic glucocorticoids a better absorbed through lipid barriers. Cell membranes and the blood-brain barrier are examples of lipid barriers.

A third important difference between natural and synthetic glucocorticoids is the half-life. The half-life of a biologically acting agent is the length of time it takes for the initial amount of the administered agent to be reduced by half. This means that a drug with a short half life will be metabolized and excreted more quickly than a drug with a long half life. Drugs with longer half lives are said to be longer-acting. Synthetic glucocorticoids are generally longer-acting than natural glucocorticoids.

The pharmacologic group of commonly used synthetic glucocorticoids includes hydrocortisone, cortisone, prednisone, prednisolone, methylprednisolone, traimcinolone, betamethasone, dexamethasone, and paramethasone among others.

The group of short-acting glucocorticoids are fully active for about 8 to 12 hours. The short-acting glucocorticoids include hydrocortisone and cortisone. Hydrocortisone is available in over-the-counter topical preparations. However, hydrocortisone is also used as intravenous "stress dose steroids" in hospitalized patients.

The intermediate-acting group of glucocorticoids maintain full efficacy for about 18 to 36 hours. The group of intermediate-acting glucocorticoids include prednisone, prednisolone, methylprednisolone and traimcinolone. Prednisone is also known as Orasone or Deltasone. Triamcinolone is commonly known as Aristocort and often used topically.

Finally, the long-acting group of glucocorticoids are fully active within the body for about one to three days. Glucocorticoids which fall in to the long-acting group include betamethasone, dexamethasone, and paramethasone. Dexamethosone is also called Decadron, while betamethosone may be known as the medication Celestone.

Of all synthetic glucocorticoids, hydrocortisone, cortisone and methylprednisolone have the highest amount of salt-retaining mineralocorticoid activity. Methylprednsilone and prednisone have a smaller degree of mineralocorticoid activity in comparison.

Synthetic glucocorticoids differ from naturally produced glucocorticoids in several ways. These differences are important in determining which synthetic glucocorticoid is appropriate for pharmacologic use in an ill individual.

Source:

Ramachandran, A. Pharmacology Recall. Lippincot Williams & Wilkins. 2000.