Green’s Dictionary of Slang

fix n.3

[it ‘fixes’ one’s emotional and/or physical state]

1. [1930s+] (drugs) an injection of a narcotic which ‘fixes one up’ when one is ‘sick’; the usual presumption being that the drug is heroin.

2. [1960s–70s] (drugs) a small amount of cocaine or heroin.

3. [1960s+] an ingestion of any drug.

4. [1960s+] (US) a compulsive desire or thrill.

5. [1980s+] anything that satisfies a craving, e.g. for food.

6. a hypodermic syringe.