biochemedic and JFK have hit the nail on the head.
Extracts would be, by far, the easiest way to go. There's likely far to many preservatives in Dr P's to use even flat..........
You'd have to check the label, but sulphites, sodium benzoate, etc are commonly used in drinks.
Besides, why try to make one distinctive alcoholic drink mimic another, non-alcoholic drink which has an equally distinctive, yet completely different flavour ?
If you want to get hammered, just drink vodka and Dr P's or get the extract to make Dr P's flavoured vodka. If you used Everclear with the extract, you could drink it in tiny vodka glasses and still get completely out of your tree on it..........