Assays - Amphetamine

Determination of Desmethylselegiline, Methamphetamine and Amphetamine - the main metabolites of Selegiline in plasma by HPLC after derivatization

Author: H.J. Mascher, B. Göd, C. Kikuta
Publisher: J. Liqu. Chrom and Rel. Technol. 20 (1997), 797-809

Determination of desmethylselegiline, methamphetamine and amphetamine in plasma requires a very sensitive and selective method. These substances are metabolites of the MAO-inhibitor selegiline. This is the first published HPLC method which is able to determine these three substances down to a limit of quantification of 0.2 ng/ml human plasma. After extraction as free bases into an organic solvent and reextraction as salts into an inorganic acid all three substances and an internal standard (phentermine) are derivatized for fluorescence detection after reversed phase chromatography. The recovery is better than 90 % for all substances. The linearity in the range tested (0.2 - 15 ng for each substance/ml) is very good indeed. The precision and accuracy is usually smaller than 5 %. Pharmacokinetic results are presented.

Pharmacokinetics and bioequivalence of the main metabolites of Selegiline: Desmethylselegiline, Methamphetamine and Amphetamine after oral aministration of Selegiline

Author: H. J. Mascher, C. Kikuta, A. Millendorfer, H. Schiel and G. Ludwig
Publisher: Int. J. Clin. Pharmacol. Ther. 35 (1997), 9 - 13

A bioavailability study of 2 different selegiline preparations were conducted in 20 healthy volunteers to test the bioequivalence. Almost no bioavailability study of selegiline has been published. As plasma levels of selegiline are very low and the elimination half-life is very short being about 9 minutes, therefore a very sensitive and selective method for determining the 3 main metabolites desmethylseligiline (DMS), methamphetamine (MA) and amphetamine (A) was developed. After application of a single oral dose of 5 mg selegiline the Cmax values of DMS reached 5 - 6 ng/ml, of methamphetamine (MA) 6 - 7 ng/ml and of amphetamine (A) about 2 ng/ml. The AUC∞ values were with DMS about 11 ng/ml x h, with MA about 130 ng/ml x h, and with A about 50 ng/ml x h. The 90 % confidence interval was with logarithmic transformed AUC∞ values 92 - 107 % with DMS, 89 - 107 % with MA, and 64 - 104 % with A. The logarithmic transformed Cmax values showed a 90 % confidence interval of 92 - 127 % with DMS, 91 - 101 % with MA, and 90 - 103 % with A. All relevant pharmacokinetic parameters showed bioequivalence with all 3 metabolites (DMS, MA, and A)