[Metabolic Acidosis under Acetaminophen Intake - an Unordinary Side Effect]

Metabolic acidosis is common among hospitalized patients. However, in a few cases a long-term administration of acetaminophen can lead to transient 5-oxoproline accumulation and causes metabolic acidosis with high anion gap in adults. A 73-year-old man was hospitalized with Staph. aureus sepsis after right knee prosthesis infection and received analgesic treatment with acetaminophen 2 g/d and antibiotic therapy with flucloxacillin over several weeks. The patient had a protracted course of illness and was transferred to intensive care unit with progressing vigilance reduction and for metabolic acidosis with high anion gap. Further medical investigation confirmed an increased concentration of 5-oxoproline in urine. A change in antibiotic treatment, interruption of acetaminophen and administration of acetylcysteine lead to a normalization of the acid-base balance. In a patient with metabolic acidosis under acetaminophen administration, particularly in the context of sepsis, malnutrition, liver and kidney diseases as well as antibiotic treatment with flucloxacillin an accumulation of 5-oxoproline must be considered. The treatment with acetaminophen must be interrupted and acetylcysteine should be administered.