There should be three ways to interact with potions: drinking them, getting them splashed on the exterior of your body (e.g. having them thrown at you and hit you), and inhaling their vapors. These should all be fully symmetric between the player and monsters and have noticeable effects for most if not all potions.

The key missing one to implement is the “topical” potion effects. Currently, the only potion with topical effects is acid, and thrown potions only do vapor effects to the monster they hit, which is often weak and ineffective. Topical effects would probably be best implemented as working the same as quaffing the potion, or a bit weaker. This would also be useful for buffing potions that monsters throw at the hero: the vapor effects of, say, a potion of blindness are so short that it doesn’t make much sense for the monster to throw it rather than doing something else, but if blindness splashing in your eyes causes a significantly longer duration, it makes more sense.