If you want to change a vitality item, it have to be in the character's inventory.
This rule applies for exchangeable items. Pay attention to items such as Birthday Vitality Potion, Freya's Refreshing Breeze, Pa'agrio's Warm Breeze, Sweet Chocolate, Returning Hero's Vitality Replenishing Juice and Pirate Elixir and Nevit's Hourglass.
They cannot be changed after exchange.