A case report of elevated bromide levels from pyridostigmine bromide for treatment of myasthenia gravis

Purpose Elevated serum bromide levels can cause dermatological, gastrointestinal, and neurological abnormalities. As bromide and chloride are both halogens, bromide may interfere with chloride assays, causing a falsely high serum chloride concentration and a low or negative anion gap. There is a paucity of data describing bromide toxicity from high doses of pyridostigmine bromide (PB). This case report describes a patient with an elevated bromide level with neurological symptoms from a therapeutic dose of PB.Summary A 37-year-old male with myasthenia gravis secondary to type B2 thymoma following thymectomy presented in myasthenic crisis. He required mechanical ventilation and was managed with steroids, intravenous immune globulin, plasmapheresis, and PB. On day 9, the patient experienced acute agitation. He had an anion gap of 2 mEq/L and a chloride concentration of 109 mEq/L. The plasma creatinine concentration was 0.63 to 1.15 mg/dL and urine output was 0.76 to 1.79 mL/kg/h throughout his admission. All other laboratory values were normal. The daily dose of PB was 660 mg on day 9, but the patient received 76 mg of intravenous PB over the first few days of his admission with the largest dose in 24 hours equal to 48 mg. On day 10, the patient's bromide level was 37 mu g/mL. His agitation was initially managed with quetiapine, followed by PB dose reduction. To our knowledge, there are 2 cases in the literature of bromide toxicity secondary to PB. These patients experienced neurological symptoms with bromide levels of 88 to 90 mu g/mL. Bromide concentrations of more than 12 mu g/mL are associated with a higher risk of neuronal dysfunction demonstrated as disturbances on an electroencephalogram, and levels greater than 50 mu g/mL are considered toxic. While our patient's bromide level was not as high as those previously reported, no other causes for his agitation were identified.Conclusion Elevated bromide levels from therapeutic PB can occur, and monitoring of these levels should be considered.