In Cauda Venenum

They're biting their tongues. The job went sour as soon as Sir Tarkington noticed the thieves arguing in his store room about shares of loot. The melodic chime of alarm bells contrasts the hectic scrambling of the party as they look for any kind of closet or cranny to hide in. One stands by the door, ready to make a bolt for it as soon as there is any sign of escape. Another stands in the middle of the room with a crossbow and a knife, they would rather die on their feet than live on their knees or in the forced servitude of Sir Tarkington it would seem. The last cowers behind a crate, looking for any boon or sign of good fortune. After a few hurried seconds of hectic searching, fortune smiles back in the form of a small glass vial with a skull and crossbones.

Poisons and drugs are really weird to use. In my experience, it's kinda hard to use poisons without making an entire big set of rules about methods of ingestion, time limits, saves, and etc. On the other hand, I use Into the Odd and its poison rules literally just state - Poison (20s): Lose d20 str if consumed - which I find too simple. Anyway, I've come up with a smattering of houserules and other bits of content for you all, enjoy:

Poisons
"And the body begins to crumble..."
(sharpieboss)

Houserules

Poisons take three simple forms:

• Ingested: A creature must swallow an entire dose of this poison that can be laced into foods or liquids to be effected by the poison. This poison immediately works, no save required.
• Injury: A creature must be injured and get this tincture that can be applied to weapons and traps into their open wounds to be effected by the poison. The victim(s) must make a STR save, if they fail then they are effected by the poison fully, if they succeed then they muscle through the pain.
• Inhaled: A creature must inhale these powders or gases to be effected by the poison. The victim(s) must make a DEX save, if they fail then they are effected by the poison fully, if they succeed then they correctly protect their face and hold their breath. 

I really hate some D&D 5e spells and whatnot that require a save, and if it's successful then nothing happens to the victim. As a result, even when the victim saves, I try to make the poison still have some effect. These rules are already really close to D&D's rules about poison, but I think they require a lot less rolling and calculating which is nice. Poisons may also have multiple methods of application, such as a gas that can seep into injuries and be inhaled or a miasma that can be ingested and inhaled depending on distance and contact with the cloud.

Batch Of Poison

Prophetsbane - Looks like a hazy white foam and tastes of ozone, it can only be collected from the spittle of madmen.

Once this poison effects somebody by injury, they lose one of their senses below for 1D6 10 second rounds. If this poison is ingested, they lose the sense for 1D6 days. Roll 1D6 below to see the sense lost.

1-2: Sight, temporarily blinded.

3-4: Touch, drop everything, can't feel pain.

5-6: Sound, temporarily deafened.

Lustgust - Looks like gaseous velvet and tastes of sugar, it can only be collected from the breast milk of hags and witches.

Once this poison effects somebody by inhalation, they become intensely sexually attracted to dangerous things for 1D6 times 10 minutes. 

Mind-Fog - Looks like pearly oil and tastes of salt, it can only be collected from the brain fluids of the smart.

Once this poison effects somebody by ingestion, they lose 1D12 WIL. If the result is even, the victim's sight is clouded by a perpetual fog in their head for the next day. If the result is odd, the victim's mind is clouded and they cannot form any new memories for the next day.

Drugs
"I've come alive!"
(sharpieboss)

Houserules

Drugs work like this:

• Every drug has a positive, a negative, and an ability. 
• The user ingests the drug, they are immediately effected by its positive and its negative. 
• Every turn (10 seconds in combat, 10 minutes out of combat), the user makes a save with the drug's associated ability, if the save fails then the user comes down from the high and is no longer effected by the positive and short-term aspects of the negative. The negative may have long term effects, though, that might not be recoverable.
• Every time the user takes the drug more than once a day, they take 1D8 damage to the drug's associated ability.

Batch Of Drugs

Fool's Guts - Looks like ground rubies and tastes like rotten fruit, only collected from the guts of those who died heroic deaths.

This Strength based drug has the positive effect of sharpening the mind like a dagger's point, so the user's mind is no longer effected by magic, charms, deceit, intimidation, or any other mind-tricks. Although, it has the negative effect of turning the user's body into a hateful undead once they meet their fateful end, and then once the undead dies the user becomes a hateful ghost.

Liquid Lightning - Looks like a nebulous cloud in a bottle and tastes like nothing, only collected from the hearts of storms.
This Dexterity based drug has the positive effect of granting the user lightning through their veins, allowing them extreme speed and acting first in initiative while the drug is active. Although, it has the negative effect of causing crippling nausea, better have a bucket handy.

Sacrament - Looks like bubbling wet pollen and tastes of thick butter, only collected from the tears of saints.
This Will based drug has the positive effect of making the user's eyes glow with amber light. Holy things glow radiantly through walls, and evil or extra-planar horrors emanate pitch darkness. Although, it has the negative effect of reacting violently with potions or other drugs within the user's body.

The Fine Print
"I think I'm seeing things, bad, bad things."
(sharpieboss)

I didn't know where to put this bit, so I'll just put it here as a few miscellaneous points. First, I really like how drugs are handled, you could also easily convert how poisons work into drugs. So, poisons have an associated ability and no positive, although they should still probably have an ingestion method listed. Also, here's another houserule about hallucinogens and how to run hallucinations in general:

• Once a person uses hallucinogens or is under hallucinations, roll 1D6, keep the result. These are referred to as "mirage points".
• The GM can spend a mirage point to roll 1D6 on the bottom table and make the player hallucinate.

1-3: Adjective. Describe what's happening with a different set of adjectives. Give what's happening different descriptors.

4-5: Verb. Describe what's happening with a different set of verbs. Change what actions are happening right now.

6: Noun. Describe what's happening with a different set of objects. Change who and what is here right now.

Here's an example:

Raderstorf the Radiant gets hit in the face by hallucinogenic spores while trekking through a deep, dank, and damp set of tunnels and caverns. The GM rolls mirage points with a D6 and gets a 3. Raderstorf soon runs into a contaminated knight, a hulking pillar of armor and bloated flesh. Except, the GM spends a mirage point, rolls 1D6, gets a 2 (change of adjectives), and describes the plague knight to Raderstorf as exceptionally tiny, only the size of Raderstorf's thumb. Confused, Raderstorf tries to stomp the knight, only to hit its shin. After running away from the knight, Raderstorf's party runs into a raiding party of ratmen, except they haven't noticed the party yet and are just camping. Instead of seeing the ratmen sharpening blades, the GM spends yet another mirage point, rolls 1D6, gets a 5 (change of verbs), and describes the ratmen's activities as them getting drunk and sleeping. Raderstorf argues with the party a bit, describing how the ratmen are weak, but they move on and out of these stinking caves. They are finally back where they came from, and they run into the person who hired them at the cave's mouth. The GM spends the final mirage point, rolls 1D6, gets a 6 (change of nouns), and describes the noble instead as the contaminated knight he saw and tried to stomp earlier. "Protecting" his teammates, Raderstorf runs his blade through the knight, only for the hallucinations to end as he realizes that he just stabbed an influential lord and the person who was going to pay them all.

Of course, that's using the hallucination rules to an especially harsh degree, you can use it for more fun activities and whatnot. Anyway, see you guys and girls soon, and don't do anything too illegal.