The finding of d MAMP on a urine drug test may have severe consequences for the patient that go beyond health concerns, including potential dismissal from a physician’s practice, discharge from a rehabilitation facility, as well as loss of employment and loss of reputation [1-3]. Laboratories that differentiate the enantiomeric forms of the drug are limited in their choice of methods. Results for a chiral analysis are expressed as the percentage of the d-enantiomer relative to the total amount of MAMP present.

For the derivatization method 1-fluoro-2-4-dinitrophenyl-5-Lalanine amide (FDAA) also called Marfey's reagent was used [4-10]. FDAA derivatives of D-amino acids exhibit strong intramolecular bonding, which reduces their polarity relative to the corresponding Lamino acid derivatives. Consequently, the D-derivatives are selectively retained on reverse phase columns and elute later than corresponding L-derivatives. The methamphetamine in the test specimen is isolated using a Cerex PSCX solid phase extraction columns followed by derivatization using Markey’s reagent. For the non-derivatized separation a Phenomenex LUX 3u 140 × 4.6 mm column using an elution buffer of 5 mM ammonium Bicarbonate pH 11.

Of the 11,264 specimens found positive for MAMP only 198 contained significant amounts of l MAMP. In general, these concentrations were low with median concentrations of 166 ng/mL (Table 1).

Table 1: Comparison of the LUX column versus Marfey method.

The majority of d-MAMP positive specimens contained high concentrations of this enantiomer. However, concentration cannot be the sole criteria to separate the use of illicit MAMP from the legal form. We observed 5 cases with very high l MAMP. As this cannot be ascribed to inhalation, we attribute these observations to spiking of the urine to mask the presence of the d enantiomer.

The finding that about 1% of MAMP positives specimens are not due to use of the illegal form should make health care workers cautious in classifying patients as meth users. To aid in the differentiation most of this true l methamphetamine findings have low urine concentrations. Chiral analysis is a well-established method that can resolve most cases, and laboratories should provide this test upon request. An accurate interpretation should include medication review and the use of the other interpretive tools.