Abstract: Gelsemium elegans Benth. (G. elegans) is a toxic medicinal plant traditionally used to treat chronic pain, with its toxicity linked to indole alkaloids such as gelsemine and humantenmine (HMT). Chronic pain often co-occurs with depression, a condition known to disrupt host-microbiota interactions, potentially affecting drug metabolism and toxicity. However, the impact of comorbid depression on the toxicity of G. elegans remains unclear. This study investigates how depression exacerbates the neurotoxicity of G. elegans and explores the role of the gut microbiota-host metabolic axis in this process. Depression-model mice were treated with G. elegans aqueous extract, gelsemine and HMT. Multi-omics approaches, including 16S rRNA sequencing and shotgun metagenomics, were used to analyze microbiota changes under depressive conditions. Functional validation was performed using pseudo-germ-free mice, fecal microbiota transplantation, and supplementation with Clostridium species and lithocholic acid (LCA), as well as pregnane X receptor (Pxr) knockout models. The results showed that depression significantly heightened the neurotoxicity of G. elegans, gelsemine and HMT. Mechanistically, depression reduced Clostridium abundance and LCA levels, impairing PXR activation and downregulating hepatic CYP3A11 expression. This disruption of the Clostridium-LCA-PXR-CYP3A11 axis hindered the detoxification of indole alkaloids, leading to increased systemic exposure and exacerbated neurotoxicity. Restoration of this pathway through Clostridium or LCA supplementation alleviated the toxicity. These findings highlight the role of the Clostridium-LCA-PXR-CYP3A11 axis in the altered toxicity of G. elegans in a depressive state, and suggest that Clostridium species and their metabolites may serve as a potential strategy for mitigating toxicity.