Amphetamine in Human Plasma: A Sensitive and Specific Enzymatic Assay
David S. Kreuz 1 and
Julius Axelrod 2
1 Pharmacology-Toxicology Program, National Institute of General Medical Sciences, Bethesda, Maryland 20014
2 Laboratory of Clinical Science, National Institute of Mental Health, Bethesda, Maryland 20014
A sensitive and specific enzymatic-isotopic method of determining plasma amphetamine concentrations in man is described. The assay is based on the transfer of the tritiated methyl group of S-adenosyl-L-[methyl-3H]methionine to amphetamine in the presence of a partially purified N-methyltransferase from rabbit lung. With this assay as little as 10 nanograms of amphetamine per milliliter of plasma can be accurately determined. The concentrations of d- and 1-amphetamine in the plasma after 20 to 30 milligrams of the drug had been ingested by human subjects are reported.
