Here's a table for anyone that wants to add drug use to a d20 fantasy RPG (Its designed for D&D)

drug list:
(1mj) Marijuana
(2op) Opium
(3jw) Jimson weed (AKA: datura)
(4mm) Psylcybin mushrooms (AKA: magig mushrooms)
(5am) Amanita Muscaria (AKA: fly agaric, mario mushroom)
(6al) Alcohol
(7wr) Woodrose (AKA: H.B.Woodrose)
(8ca) Cacti (AKA: peyote)
(9sd) Salvia Divinorum (AKA: salvia)
(0ah) Ayahuasca
(1dr) Dream root (AKA: african dream root)
(2co) Coca (AKA: cocaine leaves)
(3wo) Wormwood (AKA: absinthe)

EFFECTS:

FOR ALL: d% for effects
1d2 if side effects
d% for side effects
duration is in hrs

(1mj) Marijuana
Duration:
1d4 (smoked)/ 2d4 (eaten or drank(in a tea))
Effects:
(00-20) - euphoria
(21-45) - heightened senses
(46-70) - better rest
(71-95) - new ideas
(96-100)- new ideas & heightened senses
Side Effects:
(00-30) - hunger
(31-50) - loss of focus
(51-70) - paranoia
(71-90) - tiredness
(91-100)- all of the above

(2op) Opium
Duration:
2d4 (smoked, eaten, drank(in a tea))
ROLL 1d10 if <7 addicted
Effects:
(00-50) - reduce pain
(51-75) - euphoria
(76-99) - all of the above
(100) - heal 100%
Side Effects:
(00-30) - impared vision
(31-60) - vomiting
(61-80) - tiredness
(81-98) - unconsciousness
(99-100)- death

(3jw) Jimson Weed
Duration:
5d4 (smoked, eaten, or drank(in a tea))
Effects:
(00-40) - euphoria
(41-98) - prophecy
(99-100)- asrtal travel
Side Effects:
(00-20) - hallucinations
(21-50) - paranoia
(51-70) - weakness
(71-80) - uncoordinated
(81-100)- death

(4mm) Psilocybin Mushrooms
Duration:
2d4 (eaten)
Effects:
(00-10) - euphoria
(11-35) - insight
(36-65) - prophecy
(66-90) - new ideas
(91-95) - true insight
(96-100)- divine insight
Side Effects:
(00-20) - paranoia
(21-70) - hallucinations
(71-90) - confusion
(91-100)- tiredness

(5am) Amanita Muscaria
Duration:
1d10 (eaten)
Effects:
(00-20) - clarity
(21-40) - insight
(41-80) - true prophecy
(81-95) - berserk
(96-98) - astral travel
(99) - true insight
(100) - divine insight
Side Effects:
(00-30) - incoherent
(31-60) - synesthesia
(61-80) - vomiting
(81-100)- unconsciousness

(6al) Alcohol
Duration:
1d4 (drank)
ROLL 1d10 if <4 addicted
Effects:
(00-30) - euphoria
(31-70) - talkativeness
(71-100)- reduce pain
Side Effects:
(00-30) - incoherent
(31-60) - vomiting
(61-90) - unconsciousness
(91-100)- impared vision

(7wr) Woodrose
Duration:
2d4 (eaten)
Effects:
(00-20) - insight
(21-50) - empathy
(51-90) - false prophecy
(91-98) - new ideas
(99) - true insight
(100) - divine insight
Side Effects:
(00-10) - incoherent
(11-60) - hallucinations
(61-90) - paranoia
(91-100)- confusion

(8ca) Cacti
Duration:
2d4 (eaten)
Effects:
(00-40) - insight
(41-65) - euphoria
(66-98) - prophecy
(99) - true insight
(100) - divine insight
Side Effects:
(00-30) - confusion
(31-60) - hallucinations
(61-70) - insomnia
(71-85) - vomiting
(86-100)- incoherent

(9sd) Salvia Divinorum
Duration:
1d2 (smoked)
Effects:
(00-30) - insight
(31-70) - prophecy
(71-80) - astral travel
(81-90) - true insight
(91-100)- divine insight
Side Effects:
(00-30) - paranoia
(31-60) - confusion
(61-95) - hallucinations
(96-100)- negation of effect

(0ah) Ayahuasca
Duration:
2d4 (drank)
Effects:
(00-50) - insight
(51-70) - euphoria
(70-90) - true insight
(91-100)- divine insight
Side Effects:
(00-40) - hallucinations
(41-90) - confusion and paranoia
(91-100)- vomiting

(1dr) Dream root
Duration:
during sleep only (eaten, smoked, or drank (in a tea))
Effects:
(00-10) - no effect
(11-100)- prophecy
Side Effects:
N/A

(2co) Coca
Duration:
1d4 (eaten)
ROLL 1d10 if <8 addicted
Effects:
(00-90) - berserk
(91-100)- euphoria
Side Effects:
(00-50) - paranoia
(51-70) - insomnia
(71-100)- confusion

(3wo) Wormwood
Duration:
1d4 (smoked)/ 2d4 (drank(in a tea))
Effects:
(00-50) - clarity
(51-90) - euphoria
(91-100)- heightened sight
Side Effects:
(00-30) - vomiting
(31-100)- none

EFFECT DEFINITIONS:

Some effects are self explanitory (death, unconsciousness, etc.).

Paranoia:
Roll 2d4 against attacking random characters and objects. You fail if roll is <4.
Only applies for the duration of the drug's effect.

Insomnia:
Roll 1d4 against being unable to sleep. You fail if roll is <7. If you fail, roll
1d10. you remain unable to sleep for this many days.

Heightened sight/senses:
Add +10 to spot checks and tracking.If Heightened senses add +10 to listen
checks as well. Only applies for the duration of the drug's effect.

Clarity:
Add +20 on concentration checks. Only applies for the duration of the drug's
effect.

Berserk:
Add +1 to strength and +2 to constitution for the duration of the drug's
effect.

Confusion:
Roll 2d4 against targeting a character at random when you preform an action.
Fail if roll is <6. Only applies for the duration of the drug's effect.

Prophecy:
Gain the ability to see the future anytime within the drug's duration. DM rolls
1d10 to see if you see true or false. 1-7=false 8-10=true.

Hallucinations:
Roll 1d10 against targeting a character at random when you preform an
action. Fail if roll is <5. If fail, roll 1d10 against targeting a character that isn't
there. Fail if roll is <3. Only applies for the duration of the drug's effect.

New ideas:
+1 skill point for a cross-class skill.

Incoherent:
-10 to all checks involving talking. Spells with verbal comands are unusable.
Only for the duration of the drug's effect.

Talkativeness:
+20 for all checks involving talking. Only applies for the duration of the
drug's effect.

Loss of focus:
-20 to all concentration checks. Only applies for the duration of the drug's
effect.

Insight:
+1 to your wisdom. Only applies for the duration of the drug's effect.

True/Divine insight:
+1 to your wisdom permenantly. If divie insight, choose a new religion as
well.

Reduce pain:
+(2d4)hp. Only applies for the duration of the drug's effect. If hp is max,
then prevent the damage instead.

Impared vision:
-10 to spot and tracking checks. Only applies for the duration of the drug's
effect.

Astral travel:
Explore other planes or places. You can see traps, enimies, and items in
this state. If other planes, roll 1d20. If roll is >15, apply divine insight
talking to a god/goddess.

Synesthesia:
-10 for all checks involving perception. Only applies for the duration of the
drug's effect.

Euphoria:
-2 to all initiative checks and +1 to charisma. Only applies for the duration
of the drug's effect.

Hunger:
Player must eat once an hour. If they don't eat once an hour, then they lose
-1 to all abilities other than Constitution and -10 to all skill checks. This is
cumulative, so if its been two hours since you last ate, then you lose -2 to all
abilities except Constitution.

ADDICTION:


For Opium and Coca roll to check if you're addicted to the substance. If you are
addicted, you need to take the drug once every 1d4 days, or you will suffer withdrawal
symptoms.

Roll(1D20) Cold-Turkey(CT)-Effect
1 Trembling (-4RK, -3 DE for duration of CT.)
2 Concentration problems (-4 IN for duration of CT.)
3 Sweating (-2 CO for duration of CT.)
4 Dizziness (RK -8, -5THACO, no ranged weapons for duration of CT.)
5 Rashes (-2 CH for duration of CT.)
6 Obsession (-4 WI,desperately search of drugs for duration of CT.)
7 Alignment change (chaotic-lawfull, evil-good, for duration of CT. If neutral, change
to chaotic evil.)
8 Queasiness (can't eat anythin for duration of CT.)
9 Cramps (pain, no spells, no armor, 1 DP/day for duration of CT.)
10 Insanity (Roleplay! for duration of CT.)
11 Disease (DM chooses what sort of disease for duration of CT.)
12 Nightmare (cannot sleep good, -1 on all atributes for duration of CT.)
13 Deafness (cannot hear anything for duration of CT.)
14 Paranoid (is afraid of everything, very fearful for duration of CT.)
15 Aggressiveness (Roleplay, -4 on all reactions for duration of CT.)
16 Depressions (Roleplay, -3 on all reactions for duration of CT.)
17 Schizophrenia (everything what the "disease" makes. for duration of CT+2W4
weeks.)
18 Fuddle (Effect of the drug, which th PC is atticted to,for duration of CT.)
19 You're cured of withdrawl!
20 (-1 to wisdom permanently. Divine insight negates this)

NOTES...

Druids and Rangers are the only characters that automatically know what each drug is (Unless it is bought specifically). Other classes have to use a skill check on Knowlage (Natural). Roll 1d20. if the roll is <18 then roll 1d10 for random.


RANDOM DRUG TABLE:

1=Dream Root 2=Marijuana 3=Wormwood 4=Woodrose 5=Savlia Divinorum
6=Psylocybin Mushrooms 7=Amanita Muscaria 8=Opium 9=Opium 10=Jimson Weed


On how to take drugs:
SMOKED: Characters need to have a pipe or be able to craft one(skill check for
craft(other)) to ingest drugs in this manner.
DRANK: Characters need a flask or glass to ingest or carry drugs in this manner. If
it's drank in a tea, then you need a teapot to make it in and a glass to
ingest or carry the drug.
EATEN: Characters simply need to be able to open their mouths to ingest these
drugs.