The PHNP sees a 64-year-old man and conducts a geriatric depression scale assessment. The score is 12, indicating depression. The PHN decides to initiate fluoxetine (Prozac). Another diagnosis in his chart is heart failure. In reviewing the patient's medications, the PMHNP notes that the patient takes a calcium channel blocker (CCB). CBs mixed with fluoxetine may result in:

A - bradycardia.
B - tachycardia.
C - sick sinus syndrome.
D - valve