Why does he need vitamins? Almost all dogs food (especially the 4-5 star ones) have adequate vitamins for all life stages. Adding vitamins might upset the balance. Unless the vet says he needs vitamins, I'd skip this.
I would be very careful. Over supplementing can do more harm than good, especially if you are feeding kibble.
If you think he needs more vitamins in his diet you need to change what you are feeding, or add more fresh foods to his current diet