Hello, First of all you should be well aware that all the medications you take can have its influence on your central nervous system. The drugs you mentioned in general have moderate interaction with each other but that doesn t mean that you should stop them. It s just that you should be cautious while using it. Never change the dosage on your own and never double dose the drug yourself. These drugs zonisamide and Trazadone can increase drowsiness and might cause confusion depending on your age. So avoid driving and other activities that needs focus and attention while using it. The other interaction between Zonisamide and Vicodin is negligible. Zonisamide can sometimes increase the rate at which Vicodin is removed from your body which means the duration of action of the medication. It might be less than expected. Again, never increase the dose on your own as your doctor would have considered everything before prescribing you the drugs. Hope I have answered your query. Let me know if I can assist you further. Regards, Dr. Manoj Pradeep