Peripheral Neuropathy Induced by a Short Course of Metronidazole: A Case Report of Diagnostic Challenge.

Metronidazole is a commonly used antibiotic with a good safety and economic profile, but it may rarely be neurotoxic, causing peripheral neuropathy and encephalopathy. Most literature suggests that prolonged drug therapy, that is, a duration of > 4 weeks and a dosage of > 42 g, is associated with neurotoxicity, though the exact dose-dependent drug's relationship with neurotoxicity has not been discovered yet. We herein describe a case of a 41-year-old male diagnosed with a liver abscess and treated with a cumulative dose of 12 g of metronidazole before the onset of peripheral neuropathy. Peripheral neuropathy worsened due to the continuation of the same treatment. The possibility of metronidazole-induced peripheral neuropathy was suspected after ruling out all the other causes. NCS suggested multiple sensorimotor demyelinating polyneuropathy in all four limbs, contrasting with most of the literature, which mentioned axonal degeneration in the case of metronidazole toxicity, but in line with some literature that has mentioned demyelination as the suspected mechanism. However, the exact mechanism of toxicity is yet to be uncovered. Improvement was noted within 5 days of stopping the drug, which further confirmed the diagnosis.