Heroin (IV) ~6x

GHB ~8x

Ethanol ~10x

Methamphetamine ~10x

DXM ~10x

Cocaine ~15x

MDMA ~16x

Codeine ~20x

Methadone ~20x

Mescaline ~24x

Flunitrazepam ~30x

Ketamine ~40x

Phenobarbital ~50x

Nitrous oxide ~150x

LSD ~1000x

Cannabis/THC ~1000x or greater

Citation: Gable RS. Comparison of acute lethal toxicity of commonly abused psychoactive substances. Addiction. 2004;99(6):686–696. doi:10.1111/j.1360-0443.2004.00744.x