Joker Venom

More correctly a neurotoxin than a narcotic. Generally delivered through dermal contact but equally deadly if delivered intravenously, ingested, or inhaled as aerosol. This toxin is one of the deadliest poisons to be found in the Gotham underworld, and was developed by its namesake who generally controls its availability singlehandedly as a trademark. The telltale result is the rictus grin particular to its victims as they laugh hysterically until they suffocate or their hearts explode.

There is a variant of diluted Joker Venom laced with Ecstasy. Called "Chuckles", it exploded onto the rave scene in Gotham some years back and is considered the worst urban drug epidemic since heroin.