Yellow Xanax is also recognized as R039 tablets. The pharmaceutical creator imprints this code to make its identification unique. R039 pills contain the active alprazolam in the 2mg ratio, enabling it to function inside the system. Furthermore, the yellow and white Xanax bar is highly compatible in the mechanism rate but may vary in the prices. The cost of 1 pill of R039 pill is around $4 over the counter. It is a short term acting benzodiazepine, and thus, it begins its function within hours, and effects may last up to 6 hours. Sometimes, effects may vary from recommended duration due to other medication and health status.