Like all shooters, it is intended for consumption in one mouthful, with the explicit intention of becoming inebriated within a short time. As well as harmful to the health, they can be highly harmful to the wallet, as bars typically charge exorbitant prices for them.
This is also known as a Buttery Nipple, though the Buttery Nipple is often thought to be composed of 1/2 Butterscotch and 1/2 Irish Cream. Note that Baileys does not have to be used, but any type of Irish Cream may be.