Methods: We present a 60 year-old man who presented with altered mental status and agitation. Four days prior to admission, he took amoxicillin for dental prophylaxis and had transient agitation. Amoxicillin was taken again the day prior to admission and 12 hours post-procedure, patient became agitated, had fever, headache, neck pain, and photophobia. He presented to ER and LP was performed. cerebrospinal fluid (CSF) had 113 nucleated cells with a monocytic pleocytosis. Empiric antibiotics, including ampicillin were started. Patient’s mental status worsened and his fevers persisted. All cultures were negative and antibiotics were stopped by Infectious Disease. He subsequently but slowly improved. Upon further questioning, he had two prior episodes of meningitis in 2011, and 2015, each occurring after amoxicillin prophylaxis for dental procedures. CSF in both episodes had lymphocytic pleocytosis and was consistent with aseptic meningitis. Based on his history, there was no indication for dental prophylaxis.
Results: Aseptic meningitis has multiple non-infectious etiologies including drugs, malignancy, and autoimmune diseases. Amoxicillin-induced aseptic meningitis (AIAM) is a rare adverse reaction with 12 reported cases. The pathogenesis is unknown and clinical signs and CSF findings vary greatly. Thus, AIAM is a diagnosis of exclusion. Given amoxicillin was administered prior to each episode of meningitis in our patient, amoxicillin is the causative agent in each case. We suspect he worsened after admission because of empiric ampicillin used for Listeria. Clindamycin was recommended for future dental infections.
Conclusion: Due to widespread and common use of amoxicillin, clinicians should be aware of this rare side effect of amoxicillin. Appropriate use of dental prophylaxis is imperative to minimize unnecessary antibiotic use. Thorough history is key for diagnosis.