Case Progression: At The Hospital, Mr. H Receives Diltiazem IV

Case progression: At the hospital, Mr. H receives diltiazem IV for rate control with the plan to convert to PO. He is on cardiac monitoring and tolerating PO. Based on the information above, what effect would you anticipate if the patient was prescribed warfarin in conjunction with the diltiazem?
* No interaction
Increased effects of warfarin
Decreased effects of warfarin
He should not be prescribed warfarin