Zilretta and Myopathy

Toxic myopathy has been observed with the chronic use or the administration of large doses of corticosteroids, often in patients with disorders of neuromuscular transmission such as myasthenia gravis or in patients receiving neuromuscular blocking agents. Fluorinated corticosteroids such as betamethasone, dexamethasone, and triamcinolone appear to cause more severe muscle atrophy and weakness than the nonfluorinated agents. Moreover, multiple-daily doses are more toxic than once-daily or, preferably, alternate-day morning doses. Steroid myopathy is generalized and sometimes accompanied by respiratory weakness and dyspnea. In some cases, it has resulted in quadriparesis. Elevations of creatine kinase may also occur, albeit infrequently. After withdrawal of corticosteroid therapy, recovery may be slow and incomplete. Therapy with corticosteroids should be administered cautiously in patients with preexisting myopathy or myoneural disorders, since these conditions may confound the diagnosis of steroid-induced myopathy. The presence of a normal serum CK level, minimal or no changes of myopathy on EMG, and type 2 muscle fiber atrophy on biopsy are helpful in suggesting steroid-induced weakness. If steroid myopathy is suspected, a dosage reduction or discontinuation of the steroid should be considered.