EMIT-d.a.u. monoclonal amphetamine/methamphetamine assay. I. Stereoselectivity and clinical evaluation.

The stereoselectivity, cross-reactivity and clinical performance of the EMIT-d.a.u. monoclonal amphetamine(A)/methamphetamine (MA) immunoassay (EM) were evaluated. The cut-off calibrator of the assay was 1000 ng/ml S(+)MA. Analysis of drug-added urines and 72 clinical specimens demonstrated a cut-off for S(+)-amphetamine of approximately 400 ng/ml. The stereoisomeric selectivity of the assay was determined in a concentration vs. response manner by adding pure S(+) or R(-)isomers of A and MA, to drug free urine. The EM assay demonstrated a high selectivity for S(+)-isomers with only one of 16 urine specimens collected following excessive use of nasal inhalers yielding a positive result. This specimen contained 6000 ng/ml R(-)MA. Five-hundred clinical urine specimens were simultaneously analyzed for A or MA by the EM and EMIT-d.a.u. polyclonal (EP) amphetamine assay with 131 positive results confirmed by GC/MS. In five specimens negative by EM while positive by EP, MA was present at concentrations below the 1000 ng/ml cut-off. Two ME false positive results were apparently caused by chlorpromazine (CPZ) metabolites. A study of other phenothiazines or their metabolites gave no false positive results. The possible cross reactivity of the EM assay was further studied for phenyl-isopropylamine analogs or drugs previously reported to react with the EP assay. The EM assay showed much less cross-reactivity than EP to all drugs tested.

Resolution of methamphetamine stereoisomers in urine drug testing: urinary excretion of R(-)-methamphetamine following use of nasal inhalers.

The objective of this study is to determine whether R(-)-methamphetamine inhaled from nasal inhalers produces positive methamphetamine results in currently used urine drug screening procedures and to present a rapid method for distinguishing the optical isomers of methamphetamine. Urine from three subjects inhaling from a Vicks Nasal Inhaler every 20 min for six hours tested positive for methamphetamine by EMIT, Toxilab, TDx, and GC/MS. The chiral derivatizing reagent N-trifluoroacetyl-L-prolyl chloride (L-TPC) was used to form methamphetamine diastereomers allowing rapid identification of each stereoisomer of methamphetamine present in the urine samples. Urine samples positive for amphetamines during routine drug screening were determined to consist of a racemic mixture of methamphetamine. The isomeric composition of methamphetamine present in a urine sample indicates the probable source of the drug.

Ingestion of boric acid by infants.

Boric acid solution was inadvertantly used to dilute concentrated formula and was fed to 24-day-old and 14-month-old siblings. Total amounts ingested were 2.6 g and 1.95 g, respectively. Symptoms of toxicity included irritability, diarrhea, and perineal erythema (in the younger child only). Peak boric acid levels were 147 micrograms/ml in the 24-day-old and 56 micrograms/ml in the 14-month-old. Peritoneal dialysis was utilized in the younger child, while the older child required only symptomatic care. Serum boric acid half-lives were approximately ten hours (24-day-old) and eight hours. Neither child developed severe toxicity; both were asymptomatic at one-month follow-up.

Separation and quantitation of cis- and trans-thiothixene in human plasma by high-performance liquid chromatography.

A high-performance liquid chromatographic procedure is described for the separation of cis and trans isomers of thiothixene, a thioxanthene derivative used as an antipsychotic agent. A radial compression module (RCM-100) was used with both silica and cyanopropyl cartridges. A fixed-wavelength UV detector (254 nm) was used in these studies for quantitation. Mesoridazine is used as an internal standard because of its separation characteristics and reproducible quantitation. C18 Sep-Pak cartridges are used for biological sample clean-up. Plasma samples from patients treated with thiothixene (Navane) were assayed for cis and trans-thiothixene. No trans-thiothixene was detectable and cis-thiothixene concentrations ranged from 0 to 22.5 ng/ml.