Green’s Dictionary of Slang

1. a measure of one half grain of a narcotic.

1969		B. Jackson Thief’s Primer 107: I had some footballs, some Dilaudid.
1971		(con. 1930s) J. Brown Monkey Off My Back (1972) 55: Though Delaudid had been my favorite (I would shoot those ‘footballs’ — ½ grain — by the hatful), I was put on morphine sulphate.
1981		D.E. Miller Bk of Jargon 337: footballs: [...] Dilaudid, synthetic opiate.

2. a capsule of a psychotropic drug.

1969		R.R. Lingeman Drugs from A to Z (1970).
1977		L. Young et al. Recreational Drugs.
1980		‘Gloss. of Drug Terms’ National Instit. Drug Abuse.
2001		D. Looser Boobslang [U. Canterbury D.Phil. thesis] 72/2: football (also footie) n. 1 a temazepam capsule 2 a halcyon pill.

3. in pl., amphetamine.

1969		R.R. Lingeman Drugs from A to Z (1970) 97: footballs [from the shape?] Diphetamine pills; also, pill containing dilaudid, a synthetic opiate.
1976		R. Sabbag Snowblind (1978) 240: The most popular word is ups. Brain ticklers, browns, cartwheels, chalk, Christmas trees, coast-to-coasts, dominoes, footballs [...] are words of the sixties and are out of use now.
1981		D.E. Miller Bk of Jargon 337: footballs: Diphetamine, an amphetamine.
2001		ONDCP Street Terms 9: Footballs — Amphetamine.