mainlining

verb (used without object), main·lined, main·lin·ing. Slang.

1. to inject a narcotic, especially heroin, directly into a vein.
2. to use or enjoy something without restriction: to mainline on TV movies.

verb (used with object), main·lined, main·lin·ing. Slang.

3. to inject (a narcotic, especially heroin) directly into a vein.
4. to use, enjoy, or imbibe (something) without restriction: mainlining coffee all day long.

adjective

5. having a principal, established, or widely accepted position; major; mainstream: the membership of mainline churches.

v.also main-line, 1934, from main line in American English slang sense “principal vein into which drugs can be injected” (1933).