Ophthalmic corticosteroid therapy: systemic effects in the dog

Degenerative myopathy suggestive of glucocorticoid-induced myopathy was diagnosed in a 10-year-old female Poodle X Pekingese dog with a history of progressive lameness. Electromyography revealed bizarre high-frequency discharges. Evidence of adrenal suppression was obtained in response to exogenous ACTH. The predominant source of corticosteroid was an ophthalmic preparation used in the management of keratoconjunctivitis sicca. Considering the apparent adverse effects of the corticosteroid in this case, a study was undertaken to determine the systemic effects, if any, induced by long-term ophthalmic administration of 0.1% dexamethasone suspension in healthy adult dogs. Dogs in one group (n = 5) were treated 4 times daily for 8 weeks, and dogs in another group (n = 5) were treated 4 times daily for 16 weeks. All dogs remained healthy throughout the study, but dexamethasone-treated dogs developed marked adrenal suppression, beginning the second week of treatment and intensifying throughout the treatment period. Histopathologic changes in the liver of dexamethasone-treated dogs included scattered foci of vacuolated hepatocytes, increased hepatocytic glycogen content, and ballooning degeneration of hepatocytes. Muscle specimens were histologically, histochemically, and electromyographically normal.