The first medical use of acetaminophen occurred in 1893. Almost 30 years later, a German pharmaceutical company named Knoll synthesized hydrocodone. Then, in 1978, Knoll introduced Vicodin to the U.S., and a generic version of the drug hit the market five years later. Norco and Lortab are other well-known drugs with the same ingredients.Vicodin is available as a tablet, capsule, or liquid. In terms of potency, it rivals morphine. Vicodin works by reducing the experience of pain and producing feelings of pleasure. Hydrocodone produces the latter effect, which causes users to become addicted. Furthermore, long-term acetaminophen abuse can cause liver damage.