Quantitative Analysis of THC, 11-OH-THC, and THCCOOH in Human Hair by Negative Ion Chemical Ionization Mass Spectrometry

A sensitive and specific method was developed for the quantitative analysis of A%tetrahydrocannabinol (THC), 11-hydroxy-THC (11-OH-THC), and 11-nor-9-carboxy-THC (THCCOOH) in human hair. Deuterated internal standards were added to hair samples, and samples were digested overnight in 1N NaOH at 37~ Digest solutions were extracted with a liquid-liquid extraction procedure, which was previously developed in our laboratory for the analysis of plasma and whole blood. Derivatized extracts were analyzed on a Finnigan 4500 TM mass spectrometer in negative ion chemical ionization mode using methane as the reagent gas, hydrogen as the carrier gas, and a Restek Rtx | 200-15M-0.25-pm capillary column. The assay was linear up to 50 ng/mg hair (r, 0.99) for all three compounds and was capable of detecting 10 pg THC and THCCOOH and 100 pg 11-OH-THC on column. The intra-assay precision ranged from 2.1 to 11.2% for the three analytes; the interassay precision ranged from 4.4 to 13.0%. The method was used to detect and quantitate the presence of THC, 11-OH-THC, and THCCOOH in human hair obtained from eight regular users of cannabis. THC, but not 11-OH-THC or THCCOOH, was detectable in the hair shaft above the assay limit of quantitation. Four laboratory wash procedures were also evaluated for their effect on the measured concentration of THC in hair. In seven of eight subjects, a methylene chloride wash procedure substantially reduced the measured THC concentration by up to 50%. The gas chromatographic-mass spectrometric assay is currently being used to support pharmacokinetic studies of drug disposition into the hair of humans and animals. lowing: amphetamines, barbiturates, cocaine, phencyclidine, benzodiazepines, tetrahydrocannabinol, codeine, morphine, and heroin. Many other pharmaceuticals, such as haloperidol, buprenorphine, and amitriptyline, have also been detected in hair (27-31). However, our present knowledge of the factors that control the disposition of drugs of abuse in human hair is incomplete, and studies regarding the initial incorporation and long-term stability of the parent drug and metabolites remain to be performed. Carefully controlled, single-dose and multiple-dose experiments on human subjects will increase our understanding of the factors that control the concentration of drugs in human hair. Such studies require sensitive analytical methods for the quantitative measurement of drugs and their metabolites in human hair. The objective of this project was to develop and validate a sensitive, selective, and reliable analytical method for the detection of Ag-tetrahydrocannabinol (THC), 11-hydroxy-THC (11-OH-THC), and 11-nor-9-carboxyTHC (THCCOOH) in human hair, which could support controlled, multiple-dose pharmacokinetic studies of the disposition of these drugs into human hair. A liquid-liquid extraction procedure published previously by our laboratory for the analysis of THC and metabolites in plasma and whole blood was modified and applied to the analysis of hair (31). This paper describes the analytical method and its application to the analysis of hair samples obtained from subjects who were regular smokers of cannabis, as evidenced by self report and positive urine specimens, which were detected by Emit | (Syva Corp., Palo Alto, CA).