Good afternoon...My husband, 74 y/o, is on chemo vacation (since September 2016, pemetrexed maintenance chemo; Stage 4 NSCL cancer); he is taking apixaban (PE 03/2016), metoprolol (AFib 03/2016) and primadone (essential tremors long-standing). Our pharmacist just informed us that there is/are interaction(s) between apixaban and primadone. Savaysa (edoxaban) was prescribed in lieu of apixaban. Apixaban is $70/90-day supply from our mail order pharmacy; edoxaban is $285/90-day supply. Is there a drug that can be substituted for primidone. He is currently taking (3) 50-mg tablets primadone/daily. Or is there a substitute from apixaban that isn t as expensive, to your knowledge, as edoxaban?