Objective: To report a case of acute methemoglobinemia in a patient treated with celecoxib for osteoarthritis.
Case summary: A 72-year-old African American man developed an acute confusional state (ACS) one month after receiving celecoxib for osteoarthritis of his knee joints. There was no other identifiable cause of ACS such as any recognized cause of metabolic encephalopathy, meningoencephalitis, cerebrovascular accident, or drug intoxication. He was found to have severe methemoglobinemia (serum methemoglobin fraction 9%; reference range 0-0.2). His symptoms improved substantially, and serum methemoglobin levels decreased to 0.7% after the initiation of methylene blue therapy. He was discharged on oral riboflavin and ascorbic acid and was advised not to restart celecoxib therapy. He had not shown any recurrence of the symptoms at a follow-up visit 2 months after the withdrawal of celecoxib.
Discussion: Celecoxib is a nonsteroidal antiinflammatory drug that selectively inhibits cyclooxygenase-2. Acute methemoglobinemia can present as a syndrome of nonspecific symptoms such as headache, nausea, fatigue, dyspnea, and lethargy; these may progress to respiratory depression, coma, shock, seizures, and death. Although acute methemoglobinemia has been reported with the use of several drugs, including sulfonamides, as of August 13, 2004, this is the first case report of severe methemoglobinemia manifesting as ACS with celecoxib therapy. Use of the Naranjo probability scale indicated a probable relationship between the clinical manifestations of methemoglobinemia and celecoxib therapy in this patient.
Conclusions: Celecoxib can be associated with acute methemoglobinemia. Prompt diagnosis of this condition, withdrawal of celecoxib, and treatment with the antagonists (methylene blue, ascorbic acid, riboflavin) can reverse this potentially serious condition.