Bilirubin Elevation Caused by Naproxen Overdose: A Case Report Highlighting Laboratory Interference

BACKGROUND Overdoses on over-the-counter (OTC) drugs are increasing in the United States, which includes widely available non-steroidal anti-inflammatory drugs (NSAIDs) like naproxen. Symptoms of NSAID toxicity are well known and nonspecific, including nausea, vomiting, abdominal pain, and headaches. Extreme cases can present with confusion, seizures, and renal failure. CASE REPORT We present the case of 63-year-old man with a history of hyperthyroidism and polysubstance use who had an elevated total bilirubin level after attempting suicide via ingestion of 16 tablets of naproxen. The patient presented with vague abdominal pain and nausea in the setting of 2 weeks of worsening psychiatric symptoms, including suicidal ideation. Vital signs, physical examination, and review of systems revealed no significant findings. Medical workup was notable only for an elevated total bilirubin level; workup for hemolysis, biliary stasis, hepatic dysfunction was all within normal limits. Direct bilirubin was not elevated. The patient received intravenous fluids and antiemetic medications, and indirect hyperbilirubinemia resolved by the following day. After ruling out other causes of hyperbilirubinemia, it was determined that his elevated bilirubin was due a naproxen metabolite, O-desmethylnaproxen (ODMN), that has been shown to interfere with certain bilirubin assays when naproxen is ingested over the therapeutic dose. CONCLUSIONS Supratherapeutic naproxen ingestion can lead to laboratory findings of elevated total bilirubin in some assays due to ODMN interference. With the rise in suicide attempts in the United States with OTCs, clinicians should consider laboratory error in such clinical circumstances where the clinical data does not fit the history and physical examination.