A "4 Bar" is one of the street names for the prescription drug Alprazolam. The more popular or trade/company name for the drug is Xanex. Medically it is used to treat anxiety disorders and panic attacks. "It works by decreasing excitement in the brain"www.nlm.nih.gov" The name "4 bar" is derived from the appearance of the pill witch is scored into four sections. Xanex is usually white, while some generic versions can be yellow. The high last around 4 hours, so experienced users sometimes take more than one. The drug is highly addictive if abused.
"Man, I just popped two 4 bars and I'm feelin loaded"
"Now it's six Xanex just to feel right" -- Rick Ross