An auto mechanic accidentally has battery acid splashed in his eyes. His coworkers irrigate his eyes with water for 20 minutes, and then take him to the emergency department of a nearby hospital, where he receives emergency care for the corneal injury. The physician prescribes dexamethasone (Maxidex Ophthalmic Suspension), two drops of 0.1% solution to be instilled initially into the conjunctival sacs of both eyes every hour; and polymyxin B sulfate (Neosporin Ophthalmic), 0.5% ointment to be placed in the conjunctival sacs of both eyes every 3 hours. Dexamethasone exerts its therapeutic effect by:
A. Increasing the exudative reaction of ocular tissue.
B. Decreasing leukocyte infiltration at the site of ocular inflammation.
C. Inhibiting the action of carbonic anhydrase.
D. Producing a miotic reaction by stimulating and contracting the sphincter muscles of the iris.
Correct Answer: B. Decreasing leukocyte infiltration at the site of ocular inflammation.
Dexamethasone exerts its therapeutic effect by decreasing leukocyte infiltration at the site of ocular inflammation. This reduces the exudative reaction of diseased tissue, lessening edema, redness, and scarring. Dexamethasone is a widely prescribed drug by many healthcare professionals, including the nurse practitioner. However, it is essential to know that this potent steroid has many adverse effects, and patient monitoring is critical.
Option A: Dexamethasone is a potent glucocorticoid with very little, if any, mineralocorticoid activity. Dexamethasone’s effect on the body occurs in a variety of ways. It works by suppressing the migration of neutrophils and decreasing lymphocyte colony proliferation. The capillary membrane becomes less permeable, as well. Lysosomal membranes have increased stability.
Option C: There are higher concentrations of vitamin A compounds in the serum, and prostaglandin, and some cytokines (interleukin-1, interleukin-12, interleukin-18, tumor necrosis factor, interferon-gamma, and granulocyte-macrophage colony-stimulating factor) become inhibited.
Option D: Dexamethasone and other anti-inflammatory agents don’t produce any type of miotic reaction. In the treatment of inflammation, it is advisable to start with low doses of 0.75 mg/day, which may titrate to 9 mg/day, with dosing divided into 2 to 4 doses throughout the day. This applies to intravenous, intramuscular, and oral administrations. Less may be used when directly administered to the lesion or tissue with dosing ranging from 0.2 to 6 mg per day.
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