Rapid gas chromatographic procedure for the determination of topiramate in serum.

A rapid gas chromatographic method for the routine determination in serum of the new anticonvulsant drug topiramate (Topamax) (TOP) is described. The method involves extracting 0.50 mL of sample, previously adjusted to pH 9.5 with saturated borate buffer with ethyl acetate. One-microliter aliquots of the extract were injected into a 10-m x 0.53-mm i.d. x 0.5-microm 100% methyl silicone megabore capillary column connected to a nitrogen-phosphorus detector. The column temperature was initially at 170 degrees C for 0.1 min, then programmed at 10 degrees C/min to 240 degrees C, then 20 degrees C/min to 280 degrees C for 0.5 min. Under these conditions of the assay, the retention times of TOP and mepivicaine, internal standard, were 4.0 and 3.4 min, respectively. Quantitative determinations were performed with peak-height ratios of TOP to the internal standard. Calibration curves were linear from 2.5 to 150 mg/L TOP. The assay had a limit of quantitation of 2.5 mg/L. The overall within-run precision of the method yielded coefficients of variation (CV) of 3.9% at 10 mg/L (n = 10) and 3.1% at 100 mg/L (n = 10). The overall between-run precision calculated by three determinations on a single day for a week yielded CVs of 7.3% at 23 mg/L (n = 12) and 7.8% at 85 mg/L (n = 12). Common anticonvulsant and basic/neutral extractable drugs were found not to interfere with the assay. At present, no correlation has been demonstrated between trough plasma TOP concentrations and clinical efficacy. However, TOP values observed in our laboratory in serums from patients receiving adjunctive treatment for seizure disorders ranged from 2.5 to 35 mg/L.

Evaluation of a colloidal metal immunoassay device for the detection of tricyclic antidepressants in urine.

BACKGROUND: The sensitivity and selectivity of a colloidal metal immunoassay device (Triage Plus TCA) which is designed for the rapid detection of tricyclic antidepressant drugs in urine at a total tricyclic antidepressant concentration of 1000 ng/mL or greater were evaluated. METHODS: The sensitivity of the Triage Plus assay was determined by adding known amounts of amitriptyline, nortriptyline, imipramine, desipramine, doxepin and desmethyl-doxepin to drug free urine. The selectivity of the assay was determined by adding known concentrations of 32 drugs or drug metabolites commonly encountered in emergency department admissions to drug free urine. Triage Plus results from clinical urine specimens containing either amitriptyline, nortriptyline, imipramine, desipramine, doxepin and desmethyl-doxepin were compared to those obtained with thin layer chromatography and high performance liquid chromatography. RESULTS: Triage Plus yielded a positive response to gravimetrically prepared urines of tricyclic antidepressant at the stated cut-off value (1,000 ng/mL), and at 80% (800 ng/mL) and 50% (500 ng/mL) of the cut-off with amitriptyline, nortriptyline, imipramine, desipramine and doxepin. Other tricyclic antidepressant drugs, clomipramine and protriptyline were positive at 1000 ng/mL. Significant cross-reactivity was observed only with cyclobenzaprine at 1000 ng/mL. No significant cross reactivity was found at 1.0 g/L for 32 drugs commonly encountered in emergency department admissions. A 95% (70/74) agreement of positive tricyclic antidepressant results was observed between Triage Plus and thin layer chromatography. Discordant urines were found by high performance liquid chromatography to contain tricyclic antidepressant concentrations below the cut-off value of the colloidal metal assay. CONCLUSION: Triage Plus was found to be an accurate device for the detection of tricyclic antidepressants in urine at the stated cut-off value of 1000 ng/mL tricyclic antidepressant. With the exception of cyclobenzaprine, significant cross-reactivity was not observed with other drugs commonly encountered in emergency department admissions.

Response of the Emit II amphetamine/methamphetamine assay to specimens collected following use of Vicks inhalers.

The possible cross-reactivity of l-methamphetamine (desoxyephedrine) to the Syva Emit II amphetamine/methamphetamine assay was evaluated in urine specimens collected from seven subjects using Vicks Inhalers. The subjects were six males and one female ranging from 24 to 47 years of age. Four subjects used the inhaler every two waking hours for five consecutive days, while three subjects inhaled hourly for three consecutive days. All urine voids were collected, totaling 150 specimens. All specimens were analyzed by the Emit II assay on a Hitachi 717 automatic analyzer with a 1000-ng/mL d-methamphetamine cutoff calibrator. None of the inhaler specimens produced an Emit II response equal to or greater than the cutoff calibrator; all were negative. Specimens producing the highest rates were further analyzed by chiral GC/MS. The highest concentrations of l-methamphetamine were observed in urines from two subjects inhaling hourly: 1390, 1290, and 740 ng/mL. These specimens were collected the evenings of the second and third day. When used as directed or even with double the daily dose, Vicks Inhalers did not cause false-positive results in urine tested with the Emit II Amphetamine/Methamphetamine assay.

Evaluation of the Abbott ADx total serum tricyclic immunoassay.

The ADx total serum tricyclic antidepressant (TCA) fluorescence polarization immunoassay (Abbott Diagnostics) for the semi-quantitation of imipramine or amitriptyline and their respective N-demethylated metabolites in cases of TCA overdose was evaluated. The assay is linear from 75-1000 ng/mL total TCA in serum, and flaggs as "HI" all results exceeding 300 ng/mL. The within and between run precision of the assay for patient serum containing imipramine or amitriptyline and their metabolites gave CV's of less than 5.5% and 8.9%, respectively. A good correlation between the results of patient serum containing imipramine and desipramine simultaneously analyzed by ADx and gas liquid chromatography (GC) was observed, r2 = 0.964, n = 32. Results of patient serum containing amitriptyline and nortriptyline or doxepin and desmethyldoxepin analyzed by ADx and GC or GC-mass spectrometry were not well correlated; r2 = 0.738, n = 44 and r2 = 0.695, n = 21, respectively. The assay consistently flagged as "HI" serum with total imipramine and desipramine concentrations above 300 ng/mL by GC, and serum with greater than 360 ng/mL of amitriptyline and nortriptyline by GC/MS. No significant cross-reactivity was observed for drugs other than the TCA.

Therapeutic and toxic drug concentrations in post mortem blood: a six year study in the State of Maryland.

A six-year study of therapeutic and toxic drug concentrations in the blood from medical examiner's cases in the State of Maryland is reported. Statistical means, ranges, and number of cases are presented for three categories of cases; single drug deaths (53 drugs and 5 metabolites), multiple drug deaths (40 drugs and 5 drug metabolites), and non-drug related deaths (49 drugs and 5 metabolites). Results are compared to previous studies from the literature to facilitate, augment, and improve the understanding of the concentrations of drugs consistent with therapy or death.

The determination of amoxapine in human fatal overdoses.

Amoxapine, a recently introduced dibenzoxazepine, has been found effective in clinical studies for the treatment of various types of depression. Two amoxapine related deaths, a 53-year-old white male and a 21-year-old white female, have been investigated by this office. Both had been prescribed amoxapine for depression. Quantitation of amoxapine was by gas chromatography using a 3% OV-17 column with confirmation by ultraviolet spectrophotometry and thin layer chromatography. Blood amoxapine concentrations were found to be 18 mg/L in the first subject, and 6.7 mg/L in the second subject. These concentrations are many-fold higher than the therapeutic serum concentrations of up to 0.21 mg/L reported in a clinical study. These cases illustrate the potential lethality of amoxapine overdosage and the need for caution in prescribing amoxapine to patients with suicidal tendencies.

A method for the determination of therapeutic and toxic concentrations of tricyclic antidepressant drugs in post mortem fluids and tissues.

A sensitive and reliable procedure is presented for the measurement of the common tricyclic antidepressant (TCA) drugs in a variety of biological specimens at therapeutic as well as toxic concentrations. The method employs GC/NPD and a column packed with 3% OV-17 on Chromosorb W-HP. The pH of specimen extraction was optimized at 8.6, and 1-chlorobutane:ethyl ether (3:1) was found to be an efficient solvent for the primary extraction. Recoveries for all TCA drugs were at least 50% for each specimen. Linearity of extraction was observed over a range of therapeutic and toxic concentrations with a correlation coefficient greater than 0.99.

Blood and tissue concentrations of tricyclic antidepressant drugs in post mortem cases: literature survey and a study of forty deaths.

Blood, urine, heart, liver, and psoas muscle concentrations of tricyclic antidepressant (TCA) drugs and their N-desmethyl metabolites were determined in forty medical examiner cases. The cases were evaluated for the role played by the TCA drugs in the cause of death and compared to a literature survey of previously reported cases. The incidence of the various individual TCA drugs as a factor and the significance of the disposition of the drugs and their metabolites is included. Comparing TCA drug concentrations in the heart and skeletal muscle and considering the differences in perfusion to these organs, TCA drugs and metabolites showed an affinity for the cardiac over the skeletal muscle. The case results were correlated with experimental studies to suggest the relationships of blood concentrations with toxicity.

Synthesis and preliminary biological studies of 4- and 5-[2-hydroxy-3-(isopropylamino)propoxy]benzimidazoles: selective beta2 adrenergic blocking agents.

Benzimidazoles carrying the 2-hydroxy-3-(isopropylamino)propoxy side chain at either the C-4 or C-5 ring positions were synthesized and investigated for beta-adrenergic blocking activity. Both compounds demonstrated beta2 selectivity when evaluated in guinea pig atrial and tracheal preparations. The C-4 isomer was 17 times more selective toward tracheal tissue, and its overall potency was roughly comparable to that of propranolol. beta2 selectivity of the C-5 isomer was minimal, with a potency about one-hundredth that of propranolol.