cobras (Oh well spp.) account for a significant number of snakebite incidents in Thailand. The monoclad cobra (Naja kaouthia) has historically been considered the only non-spitting species, but recent evidence indicates population-level diversification in central and southern regions. In addition, a recently described non-spitting species, the mountain cobra (Well fuchsia), have been identified in mountainous areas. This study examines venom variation among Thai Oh well species and populations and evaluate the efficacy of monovalent and polyvalent Thai antivenoms. Proteomic analyzes showed that three-fingered toxins predominate Oh well married, mens N. fuxi shows a distinct profile enriched in snake venom metalloproteinases and cysteine-rich secretory proteins, suggesting evolutionary divergence. Electrophoretic and enzymatic analyzes showed species- and population-specific differences in phospholipase A2, acetylcholinesterase, hyaluronidase, L-amino acid oxidase, phosphodiesterase and protease activities. Cytotoxicity assays on human fibroblasts and mouse myoblasts showed that N. kaouthia (southern) and N. fuxi toxins caused the most potent and time-dependent cell damage, while central N. kaouthia and king cobra (Ophiophagus hannah) the poisons were less cytotoxic. Immunoreactivity and neutralization assays indicated that the species-specific monovalent antivenom effectively binds and neutralizes cobra venom, while neuro-polyvalent antivenom provides moderate cross-protection, and hemato-polyvalent antivenom is highly specific for viperid venom. These findings reveal significant inter- and intraspecific venom variation in Thai cobras, and emphasize the importance of population-level considerations in antivenom design and snakebite management. Continuous evaluation of venom composition and antivenom efficacy is essential to optimize clinical outcomes across Thailand’s diverse landscape.
