Green’s Dictionary of Slang

(drugs) an especially powerful drug, esp. a hallucinogen.

1975		in Spears Sl. and Jargon of Drugs and Drink (1986).
a.1989		Spears NTC’s Dict. Amer. Sl. 176: This stuff is a real headfucker. Stay away from it.
2000		JC’s bar 🌐 You don’t have to be a rocket scientist to figure out the effect a headfucker has on you. The headfucker is a combination of vodka, white rum, gin, vermouth, more vodka, some lemonade, a dash of rum and vodka, orange juice and grenadine.