β-Lactam-Induced Encephalopathy: An Underrecognized Complication Of Commonly Used Antibiotics-A Case Report

β-lactam-induced encephalopathy is an underrecognized cause of altered mental status, particularly in hospitalized patients. Despite being described decades ago, its diagnosis remains challenging.

We report the case of a 67-year-old man with septic shock secondary to Streptococcus pyogenes - mediastinitis who developed a minimally state of consciousness, psychomotor agitation, myoclonus, and dyskinesia, during treatment with different β-lactam antibiotics (ceftriaxone, amoxicillin, meropenem). Extensive neurological workup, including brain magnetic resonance imaging, cerebrospinal fluid analysis, and autoimmune testing, was unremarkable, while electroencephalography showed diffuse, non-specific slowing. A drug-induced encephalopathy was suspected. Discontinuation of β-lactam antibiotics led to rapid clinical improvement. Subsequent re-exposure resulted in recurrence of symptoms, which again rapidly resolved after drug withdrawal. This reproducible pattern strongly supported a causal relationship.

This case illustrates key features of β-lactam-induced encephalopathy. Importantly, the recurrence of symptoms following exposure to structurally distinct β-lactam agents provides compelling evidence of a class effect. The condition may occur even in the absence of severe renal failure such as our patient, highlighting the role of individual susceptibility.

β-lactam-induced encephalopathy is an underrecognized but clinically significant adverse drug reaction. Increased awareness of this condition may facilitate earlier diagnosis and prompt discontinuation of the offending agent.