Pentazocine is a synthetically-prepared narcotic drug used to treat mild to moderate pain. Pentazocine is sold under several brand names, such as Talwin.

In the 1980s, recreational drug users discovered that combining pentazocine with the antihistamine tripellenamine (most commonly dispensed under the brand name Pyribenzamine) produced a euphoric sensation much like that brought on by heroin, and users who were already addicted to the latter often used this combination when heroin was unavailable to them. Since tripellenamine tablets are typically blue in color, the pentazocine/tripellenamine combination acquired the slang name Ts and blues.

After health-care professionals and drug-enforcement officials became aware of this scenario, the narcotic-antagonist naloxone was added to preparations containing pentazocine, and the reported incidence of its abuse has declined precipitously since. Pentazocine is still classified in Schedule IV under the Controlled Substances Act in the United States, even with the addition of the naloxone.