I was just curious what the general consensus was on this. I'm a first-time DM and I have a somewhat argumentative player in the party that is quick to argue some calls so I like to be very prepared in advance with explanations. There's a part coming up where hopefully the party will just take a drink with a strong knockout roofie. I was curious about Purify Food and Drink because it says it covers poison and disease but not sleep inducing drugs. Opinions? If it isn't poison, how do you justify it?

I think that's territory where your only real defense is "because the DM and that's how I say it works." Sleep-inducing drugs aren't a thing written into the rules - so if you even open it to argument you go down the rabbit hole of "Well, it's not a poison, it's a drug." "Well, but ALL drugs are poisons if taken in sufficient quantity!" "Well, but even WATER is lethal if taken in sufficient quantity." "OK, so that means if I have Purify Food and Drink I can't drown!"

(Yes, I'm getting silly by the end, but you get the point.)

Really, all you can say if it comes up is "Purify Food and Drink is a first level spell and it's not powerful enough to counteract this particular drug, because this is a cutscene."

I'd be careful about letting poison effects circumvent a spell that is specifically designed to counteract them.

If you look at the sample poisons from the DMG, there are several 'knock out' versions.

So the game design definitely includes that type of drug in the category poison, and having the spell fail because you want it to may endanger player trust, and enjoyment of the game.

You can easily make a sleeping potion with a very high CON save. Set the DC at 20, or even 25, with a failure meaning sleep, a save meaning paralyzed but awake. (At which point you can edit your story/cutscene to include extra details for the PC that saved.) Keep in mind some races are immune to sleep effects, and some are immune to poison. 

My real question is: do they purify every drink they take? Why would you be worried about this specific instance? If the players are sharp enough to suspect a poison, then they should be allowed to avoid it. Forcing it on them even after casting a purify spell is not good. 

Purify Food and Drink would remove the knockout drugs. Basically anything in your food that you would not want to consume because it does bad things to you, that spell gets rid out.

Does the party routinely cast Purify Food and Drink on every meal they are served? That would be incredibly rude towards their hosts!

The best way to handle the potential argument is to avoid it entirely. Don't give them any reason to suspect. In the scene where they are served the drugged drink, keep the food coming and the mead flowing for a period of time. Which glass was the offending one? The first? The second? The fifth? They'll have no way of knowing, so even if they cast Purify Food and Drink on the first course/round, the poison was actually in a later course/round.

Sometimes, you get lucky. Sometimes, you have a group who was wandering in the woods for days, who found a tavern in the middle of the woods, who ran inside to get drinks despite nobody else being there beyond a bartender, and who carelessly drank themselves into locked cages with one of them, now, missing a kidney. (Then again, these are the very same people who misunderstood an obvious clue and ended up in the ocean when they were suppose to go into town.)

Sometimes, you can get away with poisoning people quite blatantly. Other times, you have to find a way to make the players think it's a good idea to do something that really isn't... and better if you can get them to think it's their own idea.

By d&d rules, a knockout drug would be a poison (wherein a failed save against the poison results in unconsciousness).

Question: Is there any way that PFaD can fail without the party knowing? I see that it has no saves and nothing that says that a higher level of casting would be required for more devious poisons which is a big problem, but is there a workaround?

How about finding a way to switch the drinks after the Purify? Is there a way to make the character with the spell burn the necessary spell slots for it and having a drink before the required rest? The flow of the adventure has to appear organic, or else, most players get suspicious (but apparently not all players). EDIT: Any way that PFaD cannot be cast - anti-magic stuff - while the players will need to drink something for some reason?

Continued edit: Someone switched potions after PFaD and they need a potion while within some anti-magic area?

My two cents:

Some people seem to be bestowing an undue amount of power on this simple little First Level spell. I feel that the simple blanket spell description leads to more questions than answers. 

First of all... it renders food and drink in the area free of poison and disease. Okay. So does that mean that ALL THE ALCOHOL in that area is no longer alcohol? Alcohol is a poison. Your wine is now Welch's grape juice. Your beer is, well.... wet bread. 

If there is chocolate in the spell's area of effect, can that chocolate now safely be fed to a dog? Does the dog also have to be in the spell's area of effect? 

If you're lactose intolerant, can you safely drink milk that was in the spell's area of effect? Has the milk changed, or have you? If the lactose in that milk has been chemically altered to suit your digestion, will the milk now taste differently to everyone else? 

And what about cheese? Cheese is just a loaf of moldy milk. Mold causes disease. Will the spell eliminate the mold? What happens to blue cheese? 

Oh, here's one... if the person casting the spell is a cannibal, will the spell remove all the poisons and diseases currently affecting another person? Suddenly a first level spell is replacing Greater Restoration! 

If there is smoking tobacco within the area of the spell's effect, will the smoking of that tobacco not contribute to lung cancer or other breathing-related diseases?

.  .  .  .  .  .  .  

You see, it seems to me that the designers of D&D, way back in the day when this spell's description was written, intended this spell to make it safe for adventurers to survive a long trek in a dungeon or wilderness without having to worry about scurvy or dysentery or under-cooked pork. But if we attempt to extrapolate the simple wording of the spell to suit our own desires, then a person clever enough could reasonably fabricate a plausible justification for dang near anything they want! 

And that's just too darn much power for a first level spell, in my humble opinion. The spell makes food and drink in a 5 foot radius safe to consume. 

The vial of poison inside the sheath of a rogue's dagger would not be neutralized, because a dagger is not food and poison is not a beverage. 

I mean, I think it's not a stretch to say that the spell does exactly what it seems like it should.

You cast it. All food and drink that are in that area becomes safe to drink. Why overthink it?

It wouldn't affect things that aren't food or drink, like the poison a rogue is storing to put on their weapon or other people.

I think it's pretty irrelevant how it would interact with real-life things that aren't well-represented in D&D, like alcohol being harmful or people having lactose intolerance. Up to the DM how they want to do it.

Spell says "All nonmagical food and drink" that means only nonmagical stuff will be affected so if you don't want the spell to work you can say that the drink is magical

Quote from soso1234 >>

Spell says "All nonmagical food and drink" that means only nonmagical stuff will be affected so if you don't want the spell to work you can say that the drink is magical

 The food itself has to be non magical. It will be rendered safe by the spell. 

If you are dead set on having that spell fail, you can find all kinds of options to justify that, but what you are doing is violating player trust. 

It is antagonistic DM'ing, and you should be aware of that before you act that way. 

The reason a player will cast that spell is because they are suspicious of someone poisoning their food. The expectation is to have safe food. if you then still retain poison, the players have wasted resources by preparing a useless spell. This spell is also from there on out completely useless for the rest of the game. 

If that is ok with you, create a magical poison that is immune to Purify Food and Drink, and disguise it with Nystuls Magic Aura.