Sentence: Exposure of LLC-PK1 cells to hydrogen peroxide ( 2.5 mM ) resulted in a significant increase in the bleomycin-detectable iron ( iron capable of catalyzing free radical reactions ) content that was prevented by cimetidine , but not ranitidine .
Drug combination annotation:
[{'class': 'POS', 'spans': ['hydrogen peroxide', 'cimetidine'], 'is_context_needed': False}, {'class': 'NEG', 'spans': [0, 2], 'is_context_needed': False}]