Risk Of Systemic Absorption

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The topical corticosteroids do not typically cause significant absorption effects when used on small areas of intact skin.

When these compounds are used on large areas of the body, however, systemic absorption may occur, especially if the skin is damaged or if occlusive dressings are used. Up to 20% to 40% of hydrocortisone given rectally may also be absorbed.

Therapeutic Uses of Adrenal Cortex Hormones

The adrenocortical steroids are used primarily for their GC effects, including immunosuppression, anti-inflammatory activity, and antiallergic activity. The MCs are used only for treatment of Addison disease. Addison disease is caused by chronic adrenocortical insufficiency and may be due to either adrenal or anterior pituitary failure. The GCs are also used in the treatment of congenital adrenal hyperplasias.

The symptoms of Addison disease illustrate the great importance of the adrenocortical steroids in the body and, especially, the importance of aldosterone. These symptoms include increased loss of body sodium, decreased loss of potassium, hypoglycemia, weight loss, hypotension, weakness, increased sensitivity to insulin, and decreased lipolysis.

Hydrocortisone is also used during postoperative recovery after surgery for Cushing syndrome—excessive adrenal secretion of GCs. Cushing syndrome can be caused by bilateral adrenal hyperplasia or adrenal tumors and is treated by surgical removal of the tumors or resection of hyperplastic adrenal gland(s).

The use of GCs during recovery from surgery for Cushing syndrome illustrates a most important principle of GC therapy: abrupt withdrawal of GCs may result in adrenal insufficiency, showing clinical symptoms similar to those of Addison disease. For that reason, patients who have been on long-term GC therapy must have the dose reduced gradually. Furthermore, prolonged treatment with GCs can cause adrenal suppression, especially during times of stress. The symptoms are similar to those of Cushing syndrome, such as rounding of the face, hypertension, edema, hy-pokalemia, thinning of the skin, osteoporosis, diabetes, and even subcapsular cataracts.

The GCs are used in the treatment of collagen vascular diseases, including rheumatoid arthritis and disseminated lupus erythematosus. Although there is usually prompt remission of redness, swelling, and tenderness by the GCs in rheumatoid arthritis, continued long-term use may lead to serious systemic forms of collagen disease. As a result, the GCs should be used infrequently in rheumatoid arthritis.

The GCs are used extensively topically, orally, and par-enterally to treat inflammatory conditions. They also usually relieve the discomforting symptoms of many allergic conditions—intractable hay fever, exfoliative dermatitis, generalized eczema, and others. The GCs are also used to treat asthmatic symptoms unresponsive to bronchodilators. They are especially useful in inhaled formulations (see section on page 863). The GCs' lymphocytopenic actions make them particularly useful for treatment of chronic lymphocytic leukemia in combination with other antineoplastic drugs.

The adrenocortical steroids are contraindicated or should be used with great caution in patients who have (a) peptic ulcer (in which the steroids may cause hemorrhage), (b) heart disease, (c) infections (the GCs suppress the body's normal infection-fighting processes), (d) psychoses (since behavioral disturbances may occur during steroid therapy),

Figure 25.30 • Ophthalmic glucocorticoids.

(e) diabetes (the GCs increase glucose production, so more insulin may be needed), (f) glaucoma, (g) osteoporosis, or (h) herpes simplex involving the cornea.

When administered topically, the GCs present relatively infrequent therapeutic problems, but their anti-inflammatory action can mask symptoms of infection. Many physicians prefer not giving a topical anti-inflammatory steroid until after an infection is controlled with topical antibiotics. The immunosuppressive activity of the topical GCs can also prevent natural processes from curing the infection. Topical steroids actually may also cause dermatoses in some patients.

Finally, as discussed previously with the oral contraceptives, steroid hormones should not be used during pregnancy. If it is absolutely necessary to use GCs topically during pregnancy, they should be limited to small areas of intact skin and used for a limited time.

Mineralocorticoid and Glucocorticoid Products

The corticosteroids used in commercial products are shown in Figures 25.29, 25.30, and 25.31. The structures illustrate the usual changes (see Fig. 25.6) made to modify solubility of the products and, therefore, their therapeutic uses. In particular, the 21-hydroxyl can be converted to an ester to make it less water soluble to modify absorption or to a phosphate ester salt or hemisuccinate ester salt to make it more water soluble and appropriate for intravenous use. The products also reflect the structure-activity relationship changes discussed previously to increase anti-inflammatory activity or potency or decrease salt retention.

Again, patients who have been on long-term GC therapy must have the dose reduced gradually. This "critical rule" and indications are discussed previously under the heading, "Therapeutic Uses of Adrenal Cortex Hormones." Dosage schedules and gradual dosage reduction can be quite complex and specific for each indication.

Many of the GCs are available in topical dosage forms, including creams, ointments, aerosols, lotions, and solutions. They are usually applied 3 to 4 times a day to well-cleaned areas of affected skin. Ointments are usually prescribed for dry, scaly dermatoses. Lotions are well suited for weeping dermatoses. Creams are of general use for many other

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Figure 25.31 • Glucocorticoids used to treat asthma and allergic rhinitis (some are also used topically).

dermatoses. When applied to very large areas of skin or to damaged areas of skin, significant systemic absorption can occur. The use of an occlusive dressing can also greatly increase systemic absorption.

The GCs that are mainly used for inflammation of the eye are shown in Figure 25.30. These compounds differ structurally from other GRs, in that the 21-hydroxyl is missing from medrysone, fluorometholone, and rimexolone, while loteprednol etabonate has a modified ester at C17 that leads to rapid degradation upon systemic absorption.

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