Kerasine is a drug in Kenichi Sonoda's Gunsmith Cats. Created by a team of chemists contraced by Goldie, kerasine is a hallucinogen that makes people susceptible to hypnotic suggestion. It became an instant hit on the streets, because each pack comes with it's own needle, and it hits similarly to LSD for "only a couple bucks mor than crack".
According to Roy Coleman, doing kerasine you can fine tune your high. A little feels like crack, do more and it hits like heroin and finish it off and it's like doing PCP and LSD.