The two forms of methamphetamine are d- and l-, with both forms registering a positive result. The d- form is usually used in prescription stimulants and appetite suppressants. The l- form is the active ingredient in an OTC inhaler such as Vick’s as well as being a metabolite of other prescription drugs.
When methamphetamine is produced as an illicit substance, it usually contains a higher amount of the d- form. During D&L analysis, the percentage of this d- isomer is revealed. If more than 20% of the d- form is present, this may indicate the illicit form of methamphetamine has been used.
When a patient tests preemptively positive for Methamphetamine and/or Dextrophan/Levorphanol, a secondary test (D/L Isomer) is automatically performed to confirm positive Methamphetamine and/or Dextrophan/Levorphanol result.