Measurement of Lysergic Acid Diethylamide (LSD) in Human Plasma by Gas Chromatography/Negative Ion Chemical Ionization Mass Spectrometry*

A method originally developed to measure LSD in urine was adapted for use with plasma. After adding a deuterium-labeled version of LSD as an internal standard, the plasma is extracted and the drug is converted to a derivative for analysis by gas chromatography combined with negative ion chemical ionization mass spectrometry. The assay produced a linear response for concentrations between 0.1 and 3.0 ng/mL. When applied to a male volunteer who took 1 microgram of LSD per kilogram of body weight orally, the peak plasma concentration reached 1.9 ng/mL three hours after dosing, and the apparent plasma half-life was 5.1 hours.

Study at a glance

Abstract

A previously reported procedure for quantification of LSD in urine was modified to permit measurement of the drug in plasma. After addition of deuterium-labelled LSD, the plasma is extracted and the extract is treated with trifluoroacetylimidazole to convert the LSD to its N-trifluoroacetyl derivative. The derivatized LSD is analyzed by capillary column gas chromatography/negative ion chemical ionization. Plasma fortified with known concentrations of LSD gave linear responses from 0.1 to 3.0 ng/mL with this assay. The method was used to determine pharmacokinetic parameters for LSD after oral administration (1 microgram/kg) to a male volunteer. The apparent plasma half-life was determined to be 5.1 h. The peak plasma concentration of 1.9 ng/mL occurred 3 h after administration.