Notes: Theophylline (Item No. 32993) is an analytical reference standard categorized as a caffeine metabolite.{62138} Theophylline has been found as an adulterant in seized heroin samples.{62139} It has also been used as a marker of authentic human urine specimens.{62138} This product is intended for use in analytical forensic applications. This product is also available as a general research tool (Item No. 23760).