Predominant Jaw Myoclonus from Cefepime Toxicity: A Case Report and a Review of the Literature

JMD Dear Sir, Cefepime is a commonly prescribed antibiotic, but the frequency and incidence of its neurotoxicity are unknown. 2 Early discontinuation after the development of neurotoxicity is crucial to recovery and to reducing morbidity and mortality. 3 The pathophysiology of cefepime-induced myoclonus is unknown. Much of the current literature does not describe debilitating jaw myoclonus. 1,3-6 Here, we expand on our two previously-reported cases of cefepime-induced jaw myoclonus 7 and introduce a new case. As in the first two cases, this case had varying degrees of renal and cardiac dysfunction 7 contributing to symptom development. Although other antibiotics were used, the resolution of symptoms after cefepime discontinuation makes it the likely cause. An 88-year-old man presented to the emergency room with shortness of breath. On admission, his temperature was 99.8 degrees Fahrenheit and his blood pressure was 80/30. The neu-rological examination was non-focal. His chest radiograph revealed a right apical infiltrate, and he was admitted with presumed pneumonia. He was given 2 grams of cefepime by intravenous (IV) daily. In addition, he was given single doses of 400 mg moxifloxacin, 360 mg gentamicin, and 1,250 mg vanco-mycin in the emergency room by IV. An IV of 500 mg metro-nidazole every 8 hours was subsequently added and continued until discharge. His creatinine and blood urea nitrogen at the time of admission were 1.7 mg/dL and 27 mg/dL, respectively and remained stable during his hospitalization. His calculated glomerular filtration rate (GFR) was 35 mL/min/1.73 m 2. Echocardiogram demonstrated an ejection fraction of 35 percent. On day three of the admission, he had transient bilateral upper extremity jerking. On day four, he had persistent myoc-lonus of the entire face, most prominently of his mouth and jaw, extending to the left side of the trapezius, with a frequency greater than 1 hertz. He was awake and communicative but dis-oriented with regard to place and time. Head CT and EEG were not performed, based on our prior experience from our two previously reported cases. 7 Cefepime was immediately stopped and replaced with ceftriaxone. His jaw myoclonus ceased, and his mental status improved the next day. Cefepime is a fourth-generation cephalosporin, commonly prescribed because of its broad coverage. Its half-life is two hours in patients with normal renal function. Because it is mainly eliminated by glomeru-lar filtration, its serum levels increase with kidney injury. Our case further demonstrates that despite appropriate renal dosing, in the …