From: Robert Swotinsky MD
Date: 23 Oct 2005
Time: 16:29:56 -0700
Remote Name: 68.166.234.126
Amphetamine and methamphetamine exist as d (dextro) and l (levo) enantiomers or stereosiomers. These designators, d and l, indicate the direction in which each enantiomer rotates a beam of polarized light. The d isomer of each substance has a strong stimulant effect on the central nervous system, while the l isomer of each substance has a less strong effect, primarily on the peripheral nerves.
Prescription amphetamine and illicit methamphetamine contain mainly the d isomer. Laboratories typically report the result(s) as just amphetamine or methamphetamine, without reporting how much is d and how much is l. (Nevertheless, many of the labs test with procedures that are more selective for d, so even if the percentages are not provided, it's likely it's mostly d.) If an MRO thinks an amphetamines-positive lab result may be due to use of Vicks Inhaler -- for example, because the result is positive for methamphetamine and negative for amphetamine and the donor says he took Vicks Inhaler -- the MRO can ask the laboratory to run additional tests that provide the percentages of d and l methamphetamine. If the lab says there is 80% or more l, that's consistent with use of Vicks Inhaler. Otherwise, it's not consistent with use of Vicks Inhaler and instead indicates use of illicit methamphetamine or a prescription drug that is metabolized to d-methamphetamine (e.g., Benzphetamine).