Sentence: The results indicate that BU and IPSA behave additively with verapamil and carbamazepine , which may be due to a common action on the same subtype of calcium channels .
Drug combination annotation:
[{'class': 'POS', 'spans': ['BU', 'IPSA', 'verapamil', 'carbamazepine'], 'is_context_needed': False}]