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Cumulative dose correlated with severity, but the design cannot establish that the drug caused the neuropathy.\nexposure: More than six months of metformin versus no metformin exposure\nevidence_span: {\"source_cache\": \"artifacts/metformin-research/19846797.abstract.txt\", \"locator\": \"Indexed abstract; zero-based, end-exclusive Unicode character offsets\", \"file_sha256\": \"801079bb07e94e223a1d7bd7fc99c9f229320aa56b6afa11700765f481558b33\", \"start_char\": 0, \"end_char\": 1789, \"text_sha256\": \"801079bb07e94e223a1d7bd7fc99c9f229320aa56b6afa11700765f481558b33\"}\n[metformin-p19846797] Association of metformin, elevated homocysteine, and methylmalonic acid levels and clinically worsened diabetic peripheral neuropathy. 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