“N-bomb” refers to any of three closely related synthetic hallucinogens (25I-NBOMe, 25C-NBOMe, and 25B-NBOMe) that are being sold as legal substitutes for LSD or mescaline. Also called “legal acid,” “smiles,” or “25I,” they are generally found as powders, liquids, soaked into blotter paper (like LSD) or laced on something edible.
These chemicals act on serotonin receptors in the brain, like other hallucinogens, but they are considerably more powerful even than LSD. Extremely small amounts can cause seizures, heart attack or arrested breathing, and death. At least 19 young people are reported to have died after taking 25I- 25C- or 25B-NBOMe between March 2012 and August 2013. People may ingest one of these drugs unknowingly, believing it to be LSD; a young man in one medical case report published in late 2014 experienced severe hallucinations and panic and attempted suicide after such an ingestion.
For more information, see https://deadiversion.usdoj.gov/drug_chem_info/nbome.pdf (PDF, 217KB)