Sentence: Recent clinical work has questioned the safety of a combined therapy of oral quinidine and intravenous verapamil , because some patients were reported to react with severe hypotension probably due to drug interactions with vascular alpha-adrenergic receptors .
Drug combination annotation:
[{'class': 'NEG', 'spans': ['quinidine', 'verapamil'], 'is_context_needed': False}]