Green’s Dictionary of Slang

1. a regular or excessive amphetamine user.

1969		R.R. Lingeman Drugs from A to Z (1970) 27: A-head [...] A frequent, habitual, often exclusive user of amphetamines.
1975		L. Bangs in Psychotic Reactions (1988) 178: There’s A-heads and there’s speedfreaks.
1981		D.E. Miller Bk of Jargon 339: A-head: A habitual amphetamine user.
1992		R. Burns Suicide Club 🌐 They weren’t totally gone like Ahab the A-Head. He was a thirty year old who looked eighty. He used to be a jazz musician, but he’d taken so much amphetamine that his brain sounded like a non-stop record player that’s skipping through all the tracks and playing a couple of lyrics from each of ten different songs.
1998		‘Weekly Wire’ Boston Phoenix 4 May 🌐 Ondine was a self-described ‘A-head,’ an amphetamine freak, who was so high during much of the taping that listening to him is like putting your ear up to a radio and scanning the stations with the volume cranked up full blast.
2002		Parenting of Adolescents ‘Drug Sl. Dict.’ 🌐 A-head: frequent amphetamine user.

2. a regular or excessive user of LSD.

1971		E.E. Landy Underground Dict. (1972).
1982		A. Shaw Dict. Pop/Rock.
2004		W. Plummer Holy Goof 125: Generally the A-head was brought down from his polychromed nirvana by the speed freak’s wired kinetics and logorrhea.