Metronidazole in treating portosystemic encephalopathy

Clinical and Neuroradiological Spectrum of Metronidazole Induced Encephalopathy: Our Experience and the Review of Literature

Metronidazole is an antimicrobial agent mainly used in the treatment of several protozoal and anaerobic infections, additionally, is often used in hepatic encephalopathy and Crohn disease. Apart from peripheral neuropathy, metronidazole can also cause symptoms of central nervous system dysfunction like ataxic gait, dysarthria, seizures, and encephalopathy which may result from both short term and chronic use of this drug and is collectively termed as "metronidazole induced encephalopathy"(MIE). Neuroimaging forms the backbone in clinching the diagnosis of this uncommon entity, especially in cases where there is high index of suspicion of intoxication. Although typical sites of involvement include cerebellum, brain stem and corpus callosum, however, lesions of other sites have also been reported. Once diagnosed, resolution of findings on Magnetic Resonance Imaging (MRI) of the Brain along with clinical improvement remains the mainstay of monitoring. Here we review the key clinical features and MRI findings of MIE as reported in medical literature. We also analyze implication of use of this drug in special situations like hepatic encephalopathy and brain abscess and discuss our experience regarding this entity.

Management of hepatic encephalopathy in the hospital

Hepatic encephalopathy (HE) develops in up to 50% of patients with cirrhosis and is a feature of decompensated cirrhosis. With the goal of reviewing the evidence for treatment and prevention of overt hepatic encephalopathy, pubmed was searched using search terms hepatic encephalopathy AND treatment, limited to human studies from January 1, 2003, through December 1, 2013, and supplemented by key references. The inpatient incidence of HE is approximately 23,000 annually, and management of these patients is common for internists and subspecialists. Treatment of the hospitalized patient with HE has changed in recent years. Treatment entails 2 phases: induction and maintenance of remission. Most cases of significant HE are precipitated by infection, gastrointestinal bleeding, medications, or other culprits. All patients should be evaluated for secondary triggers of HE, and treatment should be initiated with a nonabsorbable disaccharide (ie, lactulose) in most patients. Rifaximin (off label) can be added in patients not responding to lactulose. Neomycin is a less preferred alternative to rifaximin owing to its adverse effect profile. Other therapies, including zinc, L-ornithine-L-aspartate, and branched-chain amino acids, can be considered for patients not responding to disaccharides and nonabsorbable antibiotics. Large portosystemic shunts may be embolized in patients with medically refractory recurrent or severe HE with otherwise well-compensated cirrhosis. Molecular Adsorbent Recirculating System is now available for patients with severe HE who do not respond to medical therapy. It is critically important that patients hospitalized with significant HE continue maintenance therapy at the time of dismissal to prevent further episodes. Patients with a first-time episode of HE can be administered lactulose, and careful instructions should be provided to patients and caregivers about dose titration to achieve 3 bowel movements daily. Patients with recurrent HE episodes despite lactulose use benefit from the addition of rifaximin, which decreases the frequency of recurrent HE episodes and related hospitalizations. Last, patients and their families should be counseled about the risk of motor vehicle accidents, which require mandatory reporting to the Department of Motor Vehicles in some states.

Metronidazole-induced central nervous system toxicity: a systematic review

OBJECTIVE

To assess patient and medication factors that contribute to metronidazole toxicity.

DATA SOURCES

We searched PUBMED from 1965 through April 7, 2011, and performed a hand search of bibliographies.

STUDY SELECTION

Case reports or case series reporting metronidazole-induced central nervous toxicity.

DATA EXTRACTION

Two authors independently abstracted demographics, metronidazole indication, dose and duration, neurological manifestations, and outcomes as well as brain imaging findings.

DATA SYNTHESIS

Among 64 patients, 48 (77%) had cerebellar dysfunction, 21 (33%) had altered mental status, and 8 (15%) had seizures. Patients' ages averaged 53.3 years (range, 12-87 years), and 64% were male. The median duration of metronidazole was 54 days, although 26% had taken it less than a week and 11% had taken it less than 72 hours. Among cases with outcome data, most patients either improved (n = 18 [29%]) or had complete resolution of their symptoms with discontinuation of metronidazole (n = 41 [65%]). There was no difference in resolution of symptom by age (P = 0.71) or sex (P = 0.34). The patients with cerebellar dysfunction were less likely to experience complete resolution than those with mental status changes or seizures (relative risk, 0.67; 95% confidence interval (CI), 0.49-0.92). Nearly all patients (n = 55 [86%]) underwent imaging of the brain: 44 (69%) underwent magnetic resonance imaging (MRI) and 12 (19%) underwent computed tomographic studies. All patients with cerebellar dysfunction had abnormalities on imaging: 93% (n = 39) had a cerebellar lesion, although numerous areas in the brain were affected. On follow-up MRIs, 25 patients (83%) had complete resolution of abnormalities.

CONCLUSIONS

Metronidazole can rarely cause central nervous system toxicity; it does not seem to be a dose- or duration-related phenomenon. Most patients will have MRI abnormalities. Prognosis is excellent with metronidazole cessation.

Metronidazole-induced encephalopathy in a patient with liver cirrhosis

Encephalopathy is a disorder characterized by altered brain function, which can be attributed to various causes. Encephalopathy associated with metronidazole administration occurs rarely and depends on the cumulative metronidazole dose, and most patients with this condition recover rapidly after discontinuation of therapy. Because metronidazole is metabolized in the liver and can be transported by the cerebrospinal fluid and cross the blood-brain barrier, it may induce encephalopathy even at a low cumulative dose in patients with hepatic dysfunction. We experienced a patient who showed ataxic gait and dysarthric speech after receiving metronidazole for the treatment of hepatic encephalopathy that was not controlled by the administration of lactulose. The patient was diagnosed as metronidazole-induced encephalopathy, and stopping drug administration resulted in a complete recovery from encephalopathy. This case shows that caution should be exercised when administering metronidazole because even a low dose can induce encephalopathy in patients with liver cirrhosis.

Current and emerging strategies for treating hepatic encephalopathy

Hepatic encephalopathy (HE) is caused by liver impairment and has a multitude of symptoms in affected patients, including change in level of consciousness, intellectual function, and neuromuscular function. Pharmacologic therapy includes use of nonabsorbable disaccharides (lactulose and lactitol), and antibiotics such as neomycin, paromycin, metronidazole, and rifaximin. Probiotics, acarbose, and drugs such as L-carnitine and flumazenil, may also be helpful in treating HE.