Are there adverse effects between perphenazine and trazodone?

Yes: Both of these agents prolong the qtc interval and can result in life-threatening arrhythmias. Avoid the combo unless benefits outweigh the risks. There are other interactions as well, but this should be the one that you definitely know about.

Possibly: Per Drugs.Com drug interaction checker - trazodone plus perphenazine may ^ risk of arrythmia (especially if you have congenital long QT syndrome, electrolyte imbalances or other heart problems. )