Usage of most of drugs is regulated to some extent. While details vary with location, these are somewhat usual regulations in the Western world:

Not regulated:

Caffeine

Regulated to some extent (age or labeling requirements, for example) but available over the counter:

DXM/dextromethorphan
Acetylsalicylic acid (such as aspirin)
Paracetamol (also known as acetaminophen) (such as Tylenol)
Alcohol (although in some nations with an Islamic background, alcohol is prohibited)
Nicotine
Ephedrine and pseudoephedrine (illegal in US since Jan 2004)
Taurine

Prescription drugs, prohibited for non-medical use:

Cocaine
Codeine - available OTC in some countries as a cough remedy or in combination painkillers
GHB
Amphetamines
Anabolic steroids
Inhalants
Methadone
Morphine

Varies from tolerated to prohibited for medical use:

Cannabis
Salvia divinorum (prohibited in Australia, tolerated elsewhere)

Varies from prohibited for non-medical use to prohibited for any use

Heroin
MDMA

Prohibited for any use, no medical uses currently allowed

LSD

Drug Rehab : Lifestyle

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