I could see this being a way to initiate combat for a mage. The mage invokes his mana into the potion, with perhaps a round of lag, and then throws the potion at his enemy. Whether he hits or not could be DEX based and whether the potion just explodes in his hands during the adding of his mana to it would be INT/WIS based. If it blows up on him, the affects would happen to him. Even if he hits the enemy, there is a chance that it would just break and nothing would happen, perhaps skill % based for that. That is how I see it working.

The reasoning behind it not having to be drank to be affective is that the additional mana allows it to be absorbed through the skin. Perhaps someone with below 50% of their health would be more likely to be affected as they have open wounds.

Just a thought.