The Paladin in AD&D 2e has the class ability of Lay on Hands.
A paladin can heal by Laying on Hands. The paladin restores 2 hit points per experience level. He can heal himself or someone else, but only once per day.
Drinking a potion is described as being one of the common and simple actions a character can do in a round (including digging around in a pack for the potion, unstoppering it, etc). Other than doing that in lieu of making an attack, no penalties or disadvantages or vulnerabilities appear to be applicable.
Spell casters in combat can cast spells, but at a risk. Firstly, they get no DEX adjustment to their AC, any successful attack against them spoils the spell, and (IIRC) any threats in melee range get an Attack of Opportunity. Any touch ranged spell the caster wants to apply to an ally who is in melee combat would need to succeed with a hit vs AC 10.
So … is the Paladin's Lay on Hands ability, if used on himself, the same as chugging a potion, or does it trigger all the negatives associated with casting a spell?
Best Answer
Like a potion — but it's a a false equivalence
The spellcasting in combat rules don't apply to anything that isn't spellcasting.
As nothing suggests otherwise, there's no special handling of an attempt to lay on hands.
Note that the intuition that some actions open you up to attack is not a part of AD&D (either edition), and today usually comes from being familiar with Opportunity Attack rules from later editions. There's no such thing in AD&D. Recall also that combat rounds are abstractions of an entire minute of combat — the mess of attack and defence, of openings taken or missed, is all already part of the attack roll.
As a rule of thumb, if one finds oneself searching for a downside to a combat action that doesn't already say so, or assuming that there should be one, then one should check if they're importing ideas from another game. AD&D is not an exception-based design and can't be read the same way. Usually, an action or ability contains its entire rules, and there are no rules buried elsewhere that are relevant. AD&D wasn't designed with interlocking combat rules.
So it's like drinking a potion, but only superficially. It's not similar because it's an action of the same “type” or something like that. Lay on hands is just more similar to drinking a potion than to spellcasting, but only because most things in AD&D 2e are more like drinking a potion than like spellcasting.