The suppression of Antarctic bottom water formation by melting ice shelves in Prydz Bay

A fourth production region for the globally important Antarctic bottom water has been attributed to dense shelf water formation in the Cape Darnley Polynya, adjoining Prydz Bay in East Antarctica. Here we show new observations from CTD-instrumented elephant seals in 2011–2013 that provide the first complete assessment of dense shelf water formation in Prydz Bay. After a complex evolution involving opposing contributions from three polynyas (positive) and two ice shelves (negative), dense shelf water (salinity 34.65–34.7) is exported through Prydz Channel. This provides a distinct, relatively fresh contribution to Cape Darnley bottom water. Elsewhere, dense water formation is hindered by the freshwater input from the Amery and West Ice Shelves into the Prydz Bay Gyre. This study highlights the susceptibility of Antarctic bottom water to increased freshwater input from the enhanced melting of ice shelves, and ultimately the potential collapse of Antarctic bottom water formation in a warming climate.

Antarctic bottom water (AABW) production is critical to the global ocean overturning circulation. Here, the authors show new observations of AABW formation from seal CTD data in Prydz Bay, East Antarctica that highlights its susceptibility to increased freshwater input from the melting of ice shelves.

Estimating the cost and health status consequences of treatment with TNF antagonists in patients with psoriatic arthritis

OBJECTIVES

Tumour necrosis factor (TNF) has been shown to improve the outcomes in patients with psoriatic arthritis (PsA). We estimate the long-term impact on health status of prescribing the TNF antagonist etanercept, and evaluate the cost-effectiveness in a health economic model.

METHODS

The relationship between disability (Health Assessment Questionnaire) and health state utility was explored to estimate the quality-adjusted life years (QALYs) gained from the TNF antagonist etanercept. A model was then used to compare sequences of treatments for PsA after failure of two conventional disease modifying anti-rheumatic drugs (DMARDs). One arm commences on etanercept therapy and this is compared with a strategy commencing with combination therapy of methotrexate and ciclosporin and another commencing with leflunomide. Individual patient data from Phase III etanercept trials is used to populate the model supported by published evidence from extensive literature searches. By incorporating a life table specific for a PsA population, and using a number of evidence- and expert opinion-based assumptions for disease progression, the model was extended beyond the trial duration to a 10-yr time horizon. Cost offsets were produced by avoiding surgery through delayed progression; drug and monitoring costs were also modelled.

RESULTS

Over the 10 yrs, modelled etanercept treatment gave 0.82 more QALYs when compared with combination therapy with methotrexate and ciclosporin, and 0.65 more QALYs in comparison with leflunomide. This equates to a central estimate for the cost per QALY of pound28 189 and pound28 189 for ciclosporin and leflunomide, respectively. Sensitivity analyses demonstrated this could vary by as much as +/-28%.

CONCLUSIONS

With limited data currently available, the potential cost-effectiveness of etanercept in DMARD failures for adults with PsA appears encouraging. The result for other TNF antagonists will depend on how their relative efficacy and drug price compares with etanercept. A number of limitations are described and priorities for further research suggested.

A randomised, double blind, placebo controlled, multicentre trial of combination therapy with methotrexate plus ciclosporin in patients with active psoriatic arthritis

OBJECTIVES

To evaluate the safety and efficacy of adding ciclosporin A (CSA) to the treatment of patients with psoriatic arthritis (PsA) demonstrating an incomplete response to methotrexate (MTX) monotherapy.

METHODS

In a 12 month, randomised, double blind, placebo controlled trial at five centres in three countries, 72 patients with active PsA with an incomplete response to MTX were randomised to receive either CSA (n = 38) or placebo (n = 34). Patients underwent full clinical and radiological assessment and, in addition, high resolution ultrasound (HRUS) was performed at one centre. An intention to treat (last observation carried forward) analysis was employed.

RESULTS

Some significant improvements were noted at 12 months in both groups. However, in the active but not the placebo arm there were significant improvements in swollen joint count, mean (SD), from 11.7 (9.7) to 6.7 (6.5) (p<0.001) and C reactive protein, from 17.4 (14.5) to 12.7 (14.3) mg/l (p<0.05) as compared with baseline. The Psoriasis Area and Severity Index (PASI) score improved in the active group (2 (2.3) to 0.8 (1.3)) as compared with placebo (2.2 (2.7) to 1.9 (2.8)), p<0.001, and synovitis detected by HRUS (33 patients, 285 joints) was reduced by 33% in the active group compared with 6% in the placebo group (p<0.05). No improvement in Health Assessment Questionnaire or pain scores was detected.

CONCLUSIONS

Synovitis detected by HRUS was significantly reduced. Combining CSA and MTX treatment in patients with active PsA, and a partial response to MTX, significantly improves the signs of inflammation but not pain or quality of life.

Adequate early cyclosporin exposure is critical to prevent renal allograft rejection: patients monitored by absorption profiling

This study used receiver operating characteristic analysis to investigate the properties of area under the concentration-time curve during the first 4h after cyclosporin-microemulsion dosing (AUC0-4) and cyclosporin (CyA) levels immediately before and at 2 and 3h after dosing (C0, C2 and C3) to predict the risk of biopsy-proven acute rejection (AR) at 6 months. Ninety-eight kidney transplant recipients treated with CyA-microemulsion-based triple therapy immunosuppression were studied on post-transplant days 3, 5, and 7, and at increasing intervals thereafter. The most sensitive and specific predictor of AR was AUC0-4. Of the single time-point measurements, the measurement properties of C2 were closest to those of AUC0-4, and superior to those of C3. The relationship between C0 and subsequent AR was weak and did not reach statistical significance. On day 3, CyA AUC0-4 > or = 4,400 ng.h/mL and C2 > or = 1,700 ng/mL were each associated with a 92% negative predictive value for rejection in the first 6months. Pharmacokinetic measurements on or after day 5, and measurements on day 3 in patients with delayed graft function, were not predictive of AR. Adequate exposure within the first 3days post transplantation may be critically important in preventing subsequent rejection.

Sertraline-induced hypoglycemia

OBJECTIVE

To report a case of hypoglycemia that occurred in a patient treated with the selective serotonin-reuptake inhibitor, sertraline.

CASE SUMMARY

An 82-year-old white woman with mild cardiovascular disease and no history of glucose intolerance was seen in the emergency department for a presyncopal episode associated with a blood glucose of 32 mg/dL as measured by the ambulance attendant. She had similar symptoms the day before. Despite repeated administration of oral and intravenous glucose, the patient had recurrent episodes of hypoglycemia and was hospitalized for four days. She had started taking sertraline 50 mg once daily for mild depression 25 days prior to presentation. Other medications included furosemide 20 mg/d, ramipril 5 mg/d, clopidogrel 75 mg/d, nitroglycerin patch 0.4 mg/h, and lorazepam 1 mg taken occasionally for agitation. She had never been prescribed any oral hypoglycemic agents. Serum sertraline and desmethylsertraline concentrations measured two, three, and four days after discontinuing sertraline were within the expected range, but the rate of decline was consistent with a moderately prolonged half-life.

DISCUSSION

Sertraline has been shown to blunt postprandial hyperglycemia in rats and to potentiate the hypoglycemic effects of sulfonylurea agents in humans. It has not been reported to cause hypoglycemia independently, but in this case, a nondiabetic patient experienced multiple episodes of hypoglycemia that resolved after discontinuation of sertraline.

CONCLUSIONS

This report and another implicating fluoxetine in a case of hypoglycemia suggest that healthcare professionals should consider these medications among the possible causes of hypoglycemia occurring in patients receiving selective serotonin-reuptake inhibitors.

A simple method to estimate the required dialysis time for cases of alcohol poisoning

BACKGROUND

Conventional dialysis management of ethylene glycol and methanol poisoning includes frequent intradialytic determinations of serum toxin concentration. Dialysis is continued until a target toxin concentration is reached. Initially, the required dialysis duration is unknown, making planning difficult. We devised a simple method to estimate the duration of dialysis required and avoid quantitation of multiple toxin samples.

METHODS

Using the assumption that toxic alcohols would have a dialysis clearance similar to urea, we proposed that required dialysis time (hours) to reach a 5 mmol/L toxin concentration target would be: [-V ln(5/A)]/0.06k, where V (liters) is the Watson estimate of total body water, A is the initial toxin concentration (mmol/L), and k is 80% of the manufacturer-specified dialyzer urea clearance (mL/min) at the initial observed blood flow rate. Directly measured dialysis and renal toxin clearance, and true dialysis requirement by conventional treatment protocol were compared with our estimate in two methanol and three ethylene glycol poisonings treated with Fresenius F8 dialyzers.

RESULTS

There were no clinically or statistically significant differences between predicted dialysis duration (7.6 +/- 1.9 hours, +/-SD) and that actually provided using hourly toxin concentration sampling (7.4 +/- 1.9 hours). Renal toxin clearance was negligible compared to that of dialysis, and predicted dialysis clearance did not differ significantly from that observed.

CONCLUSIONS

The simple estimate method is sufficiently valid to guide the prescription of dialysis for toxic alcohol poisoning. Data required at dialysis start include only the initial toxin concentration, dialyzer manufacturer's specified urea clearance at initial observed blood pump speed, and patient demographics to estimate total body water. This approach allows for planned dialysis therapy, without the need for additional toxin concentration measurements until dialysis is completed.

A 6-year experience with urine drug testing by family service agencies in Nova Scotia, Canada

The objective of this study is to describe a urine drug-testing program implemented for parents with a history of substance abuse by family service agencies in the province of Nova Scotia, Canada. Nurse collectors went to the parents' home to obtain urine specimens under direct observation and then delivered the specimens to the toxicology laboratory or arranged shipment by courier under chain of custody. Each urine specimen was screened for cannabinoids, cocaine metabolite, opiates, amphetamines and benzodiazepines, ethyl alcohol and creatinine. All positive screening tests were confirmed by another method such as gas chromatography-mass spectrometry (GC-MS). In 15,979 urine specimens collected from 1994 to 1999, the percent positive rate for one (or more) drugs/metabolites ranged from 45.6% (1994-1996) to 30.0% (1998, 1999). A total of 575 specimens (3.7%) were dilute (urine creatinine <25mg/dl). Positive rates in 15,404 non-dilute specimens from 1994 to 1999 were as follows: cannabinoids - 11.7%, benzodiazepines - 11.3%, cocaine metabolite - 3.7%, and ethyl alcohol - 2.6%. Most clients provided less than 20 urine specimens for testing but some individuals submitted urine specimens more than 100 times in a 12-15-month period. Urine drug screening in parents with a history of substance abuse provided an objective and reliable indication of recent drug use in this population.

Experience with urine drug testing by the Correctional Service of Canada

The Correctional Service of Canada implemented a urine drug-screening program over 10 years ago. The objective of this report is to describe the program and drug test results in this program for 1999. Offenders in Canadian federal correctional institutions and those living in the community on conditional release were subject to urine drug testing. Urine specimens were collected at correctional facilities and shipped by courier to MAXXAM Analytics Inc. laboratory. All urine specimens were analyzed for amphetamines, cannabinoids, cocaine metabolite (benzoylecgonine), opiates, phencyclidine, benzodiazepines, methyl phenidate, meperidine, pentazocine and fluoxetine by immunoassay screening (homogeneous EIA and ELISA assays) followed by GC-MS confirmation. Ethyl alcohol was analyzed when specifically requested. Alternative screening and confirmation methods with lower cut-off values were used, whenever urine specimens were dilute (creatinine <20mg/dl and specific gravity <or=1.003). The number of urine specimens analyzed was 44,722 in 1999 and 6.2% of these specimens were dilute based on creatinine and specific gravity analysis. The positive rate for one or more drugs was 25.5% in 1999. The highest drug positive rates were for cannabinoids (10.7%), morphine (3.2%), cocaine metabolite (3.2%), codeine (2.6%), oxazepam (2.1%), temazepam (1.1%) and ethyl alcohol (1.0%). In correctional institutions (8606 non-dilute specimens analyzed in 1999), 16.4% were positive for cannabinoids, 4.9% positive for codeine and/or morphine and 2.7% positive for oxazepam and/or temazepam. In the 537 dilute specimens collected in institutions, 21% were positive for cannabinoids, 1.3% positive for codeine and/or morphine and 1.3% positive for oxazepam and/or temazepam. In the community setting, 33,928 non-dilute specimens were collected in 1999 (9.0% were positive for cannabinoids and 3.5% positive for cocaine metabolite). In the 1651 dilute specimens collected from offenders in the community in 1999, 12.6% were positive for cannabinoids and 9.5% positive for cocaine metabolite. We conclude that forensic urine drug testing provides an objective measure of drug use by offenders in Canadian federal institutions and those offenders living in the community on conditional release.

Urinary excretion profiles of 11-nor-9-carboxy-delta9-tetrahydrocannabinol: a delta9-THCCOOH to creatinine ratio study

Monitoring the major cannabinoid metabolite (delta9-THCCOOH) to creatinine ratio (M/C) has been used to predict new drug use. According to Huestis and Cone, the best accuracy (85.4%) for predicting new marijuana use was a ratio > or = 0.5 from two urine specimens collected at least 24 h apart. Manno et al. recommended an M/C ratio of > or = 1.5. Subjects with a history of chronic marijuana use were screened for cannabinoid use by immunoassay (50-ng/mL cutoff), and presumptive positives were confirmed by gas chromatography-mass spectrometry for delta9-THCCOOH (15-ng/mL cutoff). Creatinine was analyzed with a cutoff concentration of 25 mg/dL. The study objective was to apply the criteria from both groups of workers to determine if consecutive urine specimens (collected at least 24 h apart) positive for cannabinoids could be used to differentiate new marijuana use from the excretion of residual cannabinoid metabolite (delta9-THCCOOH) in an uncontrolled setting. Serial urine specimens (826) were collected from 26 individuals. Huestis and Cone and Manno et al. ratios indicated new drug use in 83% and 33% of serial urine specimens collected at least 24 h apart, respectively. Clinically, the Huestis and Cone ratio is recommended because of a lower false-negative rate (7.4%) than the Manno et al. false-negative rate (24%). In legal situations, we recommend using the Manno et al. ratio because of its lower false-positive rate (0.1%) as stated by Huestis and Cone.

Experience with a urine opiate screening and confirmation cutoff of 2000 ng/mL

Until recently, most laboratories used an opiate immunoassay screening and confirmation cutoff value of 300 ng/mL for codeine and morphine detection by gas chromatography-mass spectrometry (GC-MS). The cutoff value for opiates was increased to 2000 ng/mL or higher in various laboratories because of concerns that small doses of codeine and foods containing poppy seeds would give a positive opiate-screening result. Workplace drug-testing programs in the U.S. raised the opiate cutoff value to 2000 ng/mL on 30 November 1998. The objective of this study is to describe the results of opiate testing of 8600 urine specimens collected over 24 months with a 2000-ng/mL screening and confirmation (codeine and morphine) cutoff value. Specimens were screened by the EMITdau opiate assay using an in-house 2000-ng/mL morphine calibrator. Presumptive positive findings (N = 621) were analyzed quantitatively by GC-MS for codeine and morphine. One hundred and eighty six urine specimens were positive for codeine and morphine (> 2000 ng/mL), 298 specimens were positive for codeine only (> 2000 ng/mL) and 26 specimens were positive for morphine only (> 2000 ng/mL). All remaining specimens had codeine and morphine values < 2000 ng/mL. The codeine and morphine confirmation rate in this program reduced from 7.1% in 1994-1996 (300-ng/mL cutoff) to 2.1% in 1997-1998 with a 2000-ng/mL cutoff value. The codeine-only confirmation rate lowered from 6.6% (300-ng/mL cutoff) to 3.4% (2000-ng/mL cutoff). It was concluded that increasing opiate screening and codeine and morphine confirmation cutoff values led to > 300% reduction in the confirmed-positive rate for codeine and morphine and a 47% reduction in codeine-only confirmations in a urine drug-testing program where codeine was the major opiate used.

Glucose protection from MPP+-induced apoptosis depends on mitochondrial membrane potential and ATP synthase

MPP+ inhibits mitochondrial complex I and alpha-ketoglutarate dehydrogenase causing necrosis or apoptosis of catecholaminergic neurons. Low glucose levels or glycolytic blockade has been shown to potentiate MPP+ toxicity. We found that MPP+ caused concentration-dependent apoptosis of neuronally differentiated PC12 cells and that glucose, but not pyruvate, supplementation reduced apoptosis. Oligomycin concentrations sufficient to inhibit ATP synthase blocked the decreased apoptosis afforded by glucose supplementation. Laser-scanning confocal microscope imaging of chloromethyl-tetramethylrosamine methyl ester fluorescence to estimate DeltaPsiM showed that MPP+ and atractyloside reduced DeltaPsiM, while cyclosporin A (CSA) and glucose supplementation reversed decreases in DeltaPsiM caused by MPP+. Oligomycin blocked the effect of glucose supplementation on DeltaPsiM. These findings show that (i) MPP+-induced and atractyloside-induced apoptosis are associated with reduced DeltaPsiM; (ii) CSA maintains DeltaPsiM and reduces MPP+-induced apoptosis; and (iii) glucose supplementation maintains DeltaPsiM, likely by glycolytic ATP-dependent proton pumping at ATP synthase and reduces MPP+-induced apoptosis.

Urine drug testing for social service agencies. A Canadian experience

The introduction of urine drug testing for this program has been considered a success by the social services agencies in Nova Scotia for the following reasons: 1. The results of urine drug testing have been accepted by the Family Courts of Nova Scotia because the urine collection and testing are performed with chain of custody procedures from collection to reporting and the analysis includes confirmation of all positive immunoassay screening tests. 2. Urine drug testing (with established screening and confirmation cut-offs) provides an objective indication of recent drug use compared with relying on self-reporting of drug use. 3. Urine drug testing is believed to be a deterrent to drug use because several individuals with a history of drug use have consistently tested negative for 6 to 12 months (30% of the clients). 4. Some clients with a history of substance abuse are successful in becoming drug free with the support of the social workers and the deterrent effect of random drug testing.

Comparison of four immunoassays for the detection of lorazepam in urine

Four healthy patient subjects were each given a single, 1-mg lorazepam tablet. Urine samples from all patient subjects were collected at 12 intervals (0-2, 2-5, 5-8, 8-11, 11-14, 14-24, 24-26, 26-29, 29-32, 32-35, 35-38, and 38-48 hours). An aliquot from each urine collection was screened using cloned enzyme donor immunoassay (CEDIA), enzyme-multiplied immunoassay technique (EMIT) II, EMIT dau, and fluorescence polarization immunoassay (FPIA) without and with hydrolysis using beta-glucuronidase. Using a 200 ng/mL calibrator cut-off, none of the four immunoassays gave a positive response before hydrolyzation of the urine samples. For offline hydrolysis using Helix pomatia beta-glucuronidase, 35, 3, 0, and 4 of 48 urine samples gave positive responses on the previously listed immunoassays. The CEDIA method also gave 32 of 48 positive responses for online hydrolysis using Escherichia coli beta-glucuronidase. Online hydrolysis can be conveniently automated by including the beta-glucuronidase in the first of the two reagents combined with the urine sample.

Use and abuse of the benzodiazepines

Since chlordiazepoxide was introduced in 1961, the benzodiazepines have had many important roles in the pharmacotherapy of various disorders. This drug class for the central nervous system has been considered one of the safest in use for 35 years, especially when the benzodiazepines are compared with the barbiturates they often replaced. The objective of this article is to provide an update on the availability and distribution of benzodiazepines around the world and to discuss their most common clinical applications. Adverse effects of benzodiazepines, observed after long-term therapeutic use and after overdoses, are also presented. Triazolam is discussed because this benzodiazepine was removed from the market by regulatory authorities in the United Kingdom in 1991. Benzodiazepines will continue to have an important role in clinical medicine. Their clinical use, however, should be monitored more closely because of the greater awareness of their adverse effects after long-term use and because of the potential for misuse and abuse.

CEDIA dau Benzodiazepine screening assay: a reformulation

The CEDIA dau Benzodiazepine assay has been reformulated to include online hydrolysis of urinary benzodiazepine glucuronide conjugates. The new antibody possesses enhanced cross-reactivities toward the low-dose benzodiazepines, which are excreted at low urinary drug-metabolite concentrations. The screening method was evaluated using lorazepam as the probe benzodiazepine. Four subjects each consumed a 1-mg lorazepam tablet. Sequential urine voids over the same time intervals were collected for the next 48 h. Twelve postdose urine samples were collected from each subject. Positive results were obtained from 5-24 h to 2-35 h using a 200-ng/mL nitrazepam calibration cutoff. There was no practical difference between hydrolyzing online with the supplied E. coli beta-glucuronidase or offline with Helix pomatia beta-glucuronidase purchased separately. Without hydrolysis, all urine samples tested negative. The cross-reactivities of lorazepam in terms of nitrazepam calibration equivalents, varied from 108 to 178% for lorazepam concentrations between 50 and 2500 ng/mL. Lorazepam glucuronide gave cross-reactivities (expressed as lorazepam base) between 72 and 136% using the online hydrolysis procedure with E. coli beta-glucuronidase. Offline hydrolysis with Helix pomatia gave cross-reactivities between 84 and 134%. Without hydrolysis, lorazepam glucuronide gave less than 4% cross-reactivity in the assay.

Improved cross-reactivity to alpha OH triazolam in the BMC CEDIA DAU urine benzodiazepine assay

Immunoassays designed to detect use of older benzodiazepines such as oxazepam or diazepam often cannot detect triazolam use because of the low doses of triazolam administered, rapid biotransformation to metabolites with poor cross-reactivities, and the small amount of alpha OH triazolam glucuronide excreted in the urine. Previous studies have demonstrated that certain immunoassays have high cross-reactivity to alpha OH triazolam but are unable to detect therapeutic triazolam use in urine. The objectives of this study were to characterize the immunoreactivity toward alpha OH triazolam in the reformulated cloned enzyme donor immunoassay (CEDIA) drug abuse urine benzodiazepine assay and to measure the immunoreactivity of urine specimens from subjects who were administered single oral doses of triazolam. Alpha OH triazolam standards were prepared in drug-free urine and the new CEDIA assay gave a positive result at concentrations from 100 to 200 ng/ml, which indicates an eight-fold improvement in CEDIA cross-reactivity to alpha OH triazolam standards in the reformulated CEDIA assay. With a 200 ng/ml cut-off, 4/30 of the urine specimens screened positive for benzodiazepines without enzymatic hydrolysis and 6/30 after enzymatic hydrolysis. When using an in-house 100 ng/ml nitrazepam cut-off calibrator, 10/30 urine specimens were positive in the reformulated CEDIA assay without hydrolysis and 22/30 were positive with enzymatic hydrolysis before screening.

Mitochondrial membrane potential and nuclear changes in apoptosis caused by serum and nerve growth factor withdrawal: time course and modification by (-)-deprenyl

Studies in non-neural cells have suggested that a fall in mitochondrial membrane potential (DeltaPsiM) is one of the earliest events in apoptosis. It is not known whether neural apoptosis caused by nerve growth factor (NGF) and serum withdrawal involves a decrease in DeltaPsiM. We used epifluorescence and laser confocal microscopy with the mitochondrial potentiometric dyes chloromethyl-tetramethylrosamine methyl ester and 5,5',6, 6'-tetrachloro-1,1',3,3'-tetraethybenzimidazol carbocyanine iodide to estimate DeltaPsiM. PC12 cells were differentiated in media containing serum and NGF for 6 d before withdrawal of trophic support. After washing, the cells were incubated with media containing serum and NGF (M/S+N), media without serum and NGF, or media with the "trophic-like" monoamine oxidase B inhibitor, (-)-deprenyl. Mitochondria in cells without trophic support underwent a progressive shift to lower DeltaPsiM values that was significant by 3 hr after washing. The percentages of cells with nuclear chromatin condensation or nuclear DNA fragmentation were not significantly increased above those for cells in M/S+N until 6 hr after washing. Replacement of cells into M/S+N or treatment with (-)-deprenyl markedly reduced the proportion of mitochondria with decreased DeltaPsiM. Measurements of cytoplasmic peroxyl radical levels with 2',7'-dihydrodichlorofluorescein fluorescence and intramitochondrial Ca2+ with dihydro-rhodamine-2-acetylmethyl ester indicated that cytoplasmic peroxyl radical levels were not increased until after 6 hr, whereas increases in intramitochondrial Ca2+ paralleled the decreases in DeltaPsiM. (-)-Deprenyl appeared to alter the relationship between intramitochondrial Ca2+ levels and DeltaPsiM, possibly through its reported capacity to increase the synthesis of proteins such as BCL-2.

Oxaprozin cross-reactivity in three commercial immunoassays for benzodiazepines in urine

Immunoassay methods are commonly used to screen for drugs of abuse and some prescription drug classes as part of drug-testing programs in clinical and forensic toxicology. Oxaprozin (Daypro) is a new nonsteroidal anti-inflammatory drug that is widely prescribed in North America and has been reported to cross-react for benzodiazepines in several different immunoassay methods. The first objective of this study was to characterize the immunoreactivity of oxaprozin standards over a wide concentration range when analyzed by the EMIT dau, Abbott FPIA, and BMC CEDIA urine benzodiazepine assays. The second objective was to measure the immunoreactivity of urine specimens obtained from 12 subjects after receiving a single oral dose (1200 mg) of oxaprozin. Urine oxaprozin standards were prepared in drug-free urine at seven concentrations ranging from 500 to 100,000 ng/mL. The standards gave presumptive positive benzodiazepine results between 5000 and 10,000 ng/mL (EMIT dau) and approximately 10,000 ng/mL (FPIA, CEDIA). With a 200-ng/mL cutoff for benzodiazepines in these assays, all 36 urine specimens collected from the 12 subjects gave positive results by EMIT and CEDIA, and 35 of 36 urine specimens were positive by FPIA. It was concluded that presumptive positive benzodiazepine results by these immunoassays may be due to the presence of oxaprozin or oxaprozin metabolites. It is recommended that all positive immunoassay screening tests for benzodiazepines be confirmed by another technique based upon a different principle of analysis.

Urine drug testing for social service agencies in Nova Scotia, Canada

In Nova Scotia Canada, governmental authorities expressed concern in the late 1980s about the adverse effects of drug use by parents on the welfare of their children. Since 1991, parents with a history of drug abuse may be required to submit to urine drug and alcohol testing when ordered by the Family Courts of this province. The objective of this paper is to present this drug testing program and the results of drug testing on 125 clients from 1994-1996. Urine specimens were collected in the parents' residence by a nurse and transferred directly to the laboratory by the collector or a courier. Specimens were screened by immunoassay and TLC followed by GC-MS confirmation. Results were sent directly to the social worker. In the 3,613 urine specimens analyzed, 50.2% of specimens were negative, 45.6% were positive for one or more drug/metabolite and 4.2% of specimens were dilute (creatinine < 25 mg/dL). The distribution of positive results were: cannabinoids (11.5%), cocaine metabolite (5.0%), benzodiazepines (14.5%), codeine/morphine (7.1%), codeine (6.6%), diphenhydramine (2.2%) and ethyl alcohol (1.6%). Drug testing has been considered a success by these agencies since testing provides an objective indication of recent drug use and the overall prevalence of drug use in this drug abusing population has reduced from 100% to < 50%.

Comparative evaluation of five immunoassays for the analysis of alprazolam and triazolam metabolites in urine: effect of lowering the screening and GC-MS cut-off values

This study included evaluation of five commercially available immunoassays for the detection of alprazolam and triazolam metabolites in urine following single oral doses of these drugs. The products investigated were the EMIT d.a.u. assay, EMIT II assay, Abbott TDx (FPIA) assay, Bio Site TRIAGE device, and the Boehringer Mannheim/Microgenics CEDIA assay for urinary benzodiazepines. Urine specimens were also analyzed quantitatively by gas chromatography-mass spectrometry. Percent cross-reactivity was assessed by analysis of drug free urine containing drug standards at concentrations ranging from 100 to 10,000 ng/mL. The drug standards analyzed were alpha-OH-alprazolam, alpha-OH-triazolam, and alpha-OH-alprazolam glucuronide. The effect of lowering the screening cut-off value to 100 ng/mL, lowering the confirmation cut-off value to 50 and 25 ng/mL and the use of beta-glucuronidase hydrolysis prior to analysis was also studied. Lowering the screening cut-off value and using enzymatic hydrolysis prior to screening increased the positive detection rate for benzodiazepines with the EMIT d.a.u. assay and fluorescence polarization immunoassay (FPIA). The TRIAGE device gave the lowest percent cross-reactivity in the analysis of the drug standards and gave negative results in all urine specimens analyzed following ingestion of alprazolam and triazolam.

New drugs for the treatment of epilepsy

OBJECTIVES

This article will review current data on the metabolism, interactions, methods of analysis, and adverse effects observed with the use of new anticonvulsant drugs. The role of the laboratory in the provision of therapeutic drug monitoring for these drugs is discussed.

CONCLUSION

Certain of the newer anticonvulsant drugs require therapeutic drug monitoring for their optimal use in the treatment of epileptic seizures. The requirement for therapeutic drug monitoring has not been established for some of these drugs. Many of the newer anticonvulsant drugs, including lamotrigine, felbamate, vigabatrin, and zonisamide, interact clinically with established drugs, such as phenytoin, phenobarbital, carbamazepine, and valproic acid. Introduction of these new drugs will result in the need for more frequent monitoring of the established drugs during polytherapy. The need for a drug-monitoring service for anticonvulsant drugs overall will continue, due to the frequency of drug interactions, the incidence of adverse effects, and concerns about compliance with the dosing regimen in these patients.

Rapid detection and enumeration of Salmonella in chicken carcass rinses using filtration, enrichment and colony blot immunoassay

A strategy was developed for 24-h detection and enumeration of Salmonella spp. on processed chicken carcasses. Carcasses were rinsed with saline and the rinses spiked with known numbers of serogroup B, C, D or E Salmonella. The total rinse volume was passed through two filter units of decreasing pore size. These removed most of the extraneous material while permitting rapid passage of more than 77% of the Salmonella. At least 100 ml of the filtrate was passed through a third filter unit containing a nitrocellulose capture membrane. Captured bacteria were selectively enriched by incubating the nitrocellulose membrane on filter pads soaked in Rappaport-Vassiliadis broth and then on pads soaked in brilliant green broth containing sulfadiazine and novobiocin. A colony blot immunoassay using two anti-Salmonella monoclonal antibodies was used to identify and enumerate the captured Salmonella. As few as five Salmonella colony forming units per carcass rinse could be detected. An evaluation of this system with 24 field samples indicated that the specificity was comparable to and the sensitivity higher than that of standard culture procedures.

Evaluation of the Abbott TDx serum benzodiazepine immunoassay for the analysis of lorazepam, adinazolam, and N-desmethyladinazolam

This study involved the evaluation of the Abbott TDx serum benzodiazepine assay, a fluorescence polarization immunoassay (FPIA), for the detection of lorazepam, adinazolam, and N-desmethyladinazolam in serum. Precision of the assay was determined by using three control serums containing 75, 300, and 700 ng/mL nordiazepam. Between-run precision studies (N = 22) gave mean values of 76, 306, and 690 ng/mL with coefficients of variation of 6.5, 3.3, and 5.7%, respectively. Percent cross-reactivity of serum lorazepam standards (35-500 ng/mL) ranged from 29 to 69%. The cross-reactivity of serum adinazolam ranged from 40 to 47% between 50 and 150 ng/mL and from 38 to 55% for N-desmethyladinazolam between 50 and 250 ng/mL. Serum specimens (48) collected from individuals known to be receiving lorazepam were analyzed. Twenty-two specimens were positive for benzodiazepines. Serum specimens were collected from 0.25 to 24 h after administering a 15-mg oral dose of adinazolam to six volunteers. The FPIA results were compared with combined high-performance liquid chromatographic (HPLC) results for adinazolam and N-desmethyladinazolam. The FPIA method did not detect benzodiazepines at 0.25 h after administration of adinazolam but did detect benzodiazepines from 0.5 to 24 h after administration. The correlation between HPLC (N-desmethyladinazolam) and FPIA results by regression analysis gave the following: y = 0.937x + 4.449, r = 0.98, n = 15. It was concluded that the Abbott FPIA assay for benzodiazepines can detect lorazepam when prescribed in therapeutic doses and when present at greater than 25 ng/mL and can semiquantitatively detect adinazolam or N-desmethyladinazolam or both when present at concentrations greater than 50 ng/mL.

Analysis of diethyltoluamide (DEET) following intentional oral ingestion of Muscol

N,N-Diethyl-m-toluamide (DEET) is an effective component of several insect repellent products. A 19-year-old woman was admitted to the emergency department following ingestion of 15-25 mL 95% diethyltoluamide (Muscol). Serum and urine toxicology screening tests were negative except for detection of DEET. DEET was qualitatively identified and quantitated by gas chromatography-mass spectrometry. Concentrations of DEET based on selected ion monitoring (ion at m/z 119) were 63.0, 17.2, 1.9, and less than 0.2 mg/L in serum specimens collected at 2, 5, 24, and 48 h following ingestion, respectively. Serial monitoring of DEET concentrations and the cardiac abnormalities observed in this case following oral ingestion were not reported previously.

Lamotrigine analysis in serum by high-performance liquid chromatography

Lamotrigine is an anticonvulsant drug soon to be introduced to the North American market. It is chemically unrelated to any currently available antiepileptic drug. The objective of this study was to develop a quantitative high-performance liquid chromatography assay for lamotrigine in serum. Lamotrigine was extracted from serum at alkaline pH into ethyl acetate after addition of the internal standard (BW725C78). After mixing, the organic layer was evaporated to dryness before dissolving the residue in methanol for isocratic separation on a RP-8 column (5 microns) with a mobile phase of water/0.5 M phosphate buffer at pH 6.5/acetonitrile (790/10/200) with eluant monitoring at 306 nm. Calibration was performed with five serum standards (2-32 microM and recovery averaged 88% at 25 microM. Between-run precision was 4.1 and 2.5% C.V. at 13.6 and 31.6 microM, respectively. At room temperature, lamotrigine was stable for a minimum of 7 days. Interference studies were performed on serum specimens containing commonly monitored drugs. The only potentially interfering drug was carbamazepine, which elutes 2.5 times longer than lamotrigine. We conclude that this is a reliable method for quantitation of lamotrigine in serum.

Simple extraction of Campylobacter lipopolysaccharide and protein antigens and production of their antibodies in egg yolk

Antigens were heat extracted from Campylobacter jejuni (LI04) and C. coli (LI020) in the presence of ethylenediaminetetraacetate (EDTA) and were recovered in the supernatant of a low-speed centrifugation. The method is simpler, safer and more efficient in extracting lipopolysaccharide (LPS) antigens than the hot phenol method. The extracted antigens (LPS plus several proteins) elicited production of antigen-specific antibodies in the egg yolk of immunized hens. Antibodies purified by polyethyleneglycol fractionation were used to detect antigens fractionated on SDS polyacrylamide gel electrophoresis.

Modes of inhibition of foodborne non-Salmonella bacteria by selenite cystine selective broth

Various cell densities of six common foodborne non-Salmonella bacteria were exposed to selenite cystine (SC) Salmonella selective medium. The insensitivity of Pseudomonas aeruginosa and Proteus vulgaris to SC was confirmed. Selenite cystine selective medium was effective against the sensitive bacteria up to certain cell densities, beyond which the bacteria survived. As judged from the minimum cell number required for survival in SC, Staphylococcus aureus was the most sensitive to SC, followed by Bacillus cereus, Escherichia coli and Citrobacter freundii. When sensitive bacteria were grown in SC, they enriched resistant variants which exhibited no or reduced sensitivity to SC. The change in density of sensitive cells after exposure to SC suggested that bacterial sensitivity to SC depended on the efficiency of killing and growth inhibition by SC as well as the fraction of resistant variants in the bacterial population. Since Salmonella samples generally contain unknown numbers and types of sensitive bacteria, it is difficult to predict the effectiveness of their selective inhibition by SC.

Urinary screening for adinazolam and its major metabolites by the Emit d.a.u. and FPIA benzodiazepine assays with confirmation by HPLC

Adinazolam is a triazolobenzodiazepine, currently under clinical investigation, that possesses antidepressant and anxiolytic activity. It has a short half-life (less than 3 h), and less than 2% of an oral dose is excreted unchanged. The major urinary metabolite is N-desmethyladinazolam, and minor metabolites are estazolam and alpha-OH-alprazolam. The objective of this study was to characterize the reactivity of adinazolam, N-desmethyladinazolam, and estazolam in the Emit d.a.u. benzodiazepine assay and the Abbott TDx urine (FPIA) benzodiazepine assay. N-desmethyladinazolam and estazolam gave an equivalent response to the Emit cutoff calibrator (300 ng/mL) at 100-200 ng/mL, and adinazolam gave an equivalent response at 200 ng/mL. By FPIA, N-desmethyladinazolam and adinazolam had equivalent net polarization values as the 300-ng/mL low control at 500-1000 ng/mL, and estazolam gave a positive response at 300 ng/mL. Six volunteers received single oral doses of 10, 30, and 50 mg of adinazolam. Urine specimens (N = 7) were collected from 0 to 36 h post-administration. By Emit, all urine specimens at all doses were positive from 2 to 36 h, and all FPIA analyzed specimens were positive from 2 to 24 h. Confirmation testing was performed by HPLC by analyzing for N-desmethyladinazolam. All urine specimens were confirmed positive for N-desmethyladinazolam (greater than 200 ng/mL) except for the blank specimens (time = 0) and 7 of 18 specimens collected 36 h post-administration. In conclusion, both immunoassay screening assays are acceptable for detecting the presence of adinazolam in human urine for up to 24 h after a single oral dose of 10-50 mg.

The use of antiepileptic drug levels in children: a survey of Canadian pediatric neurologists

There are 60 pediatric neurologists in Canada. Replies were received from 56 in response to a survey regarding the use and perceived value of antiepileptic drug (AED) levels. AED levels are frequently ordered and influence clinical care. There were, however, discrepancies among pediatric neurologists regarding the upper and lower limits of the "therapeutic ranges" and the clinical application of levels. We suggest that both the value and use of AED levels needs further study.

Evaluation of the toxicity of Salmonella selective media for shortening the enrichment period

Five Salmonella serotypes recovering from heat injury exhibited different kinetics of resuscitation and growth. Exponential growth was reached before full resuscitation. Fully resuscitated cells and uninjured cells at low cell densities exhibited sensitivity when transferred from non-selective media to selective media, Rappaport-Vassiliadis (RV) and tetrathionate-brilliant green (TBG). The minimum number of cells required to survive in RV and TBG was determined and ranged from 10(2) to 10(5) CFU depending on the serotype. Salmonella grown in RV produced cell populations which exhibited no sensitivity when transferred to fresh RV even at low cell densities. Thus, toxic selective media enriched a resistant population. Selenite cystine exhibited no toxicity to resuscitated or uninjured Salmonella. The significance of these findings was discussed for the purpose of shortening the Salmonella enrichment period.

Colorimetric and gas chromatographic procedures for glycolic acid in serum: the major toxic metabolite of ethylene glycol

Monitoring of individuals poisoned with ethylene glycol involves analysis of ethylene glycol in serum. The objective of this procedure was to validate a colorimetric and gas chromatographic procedure for glycolic acid in serum. The colorimetric procedure requires no sophisticated instrumentation and has been shown to be specific for glycolic acid. A gas chromatographic procedure has also been developed involving methyl derivatization of glycolic acid and the internal standard (propionic acid). These methods have been used for the analysis of serum specimens from ethylene glycol poisoned patients. Glycolic acid has been recognized as the major toxic agent in ethylene glycol poisoning but current methods available do not allow analysis in a clinically relevant turnaround time. These two procedures allow glycolic acid quantitation by procedures readily set up in most clinical toxicology laboratories.

Urinary screening for alpha-OH triazolam by FPIA and EIA with confirmation by GC/MS

Triazolam is a very short-acting triazolobenzodiazepine with sedative-hypnotic properties. Approximately 2% of an oral dose is excreted unchanged in the urine. The major urinary metabolite is alpha-hydroxytriazolam glucuronide (70% of the dose). The objective of this study was to characterize the reactivity of alpha-hydroxytriazolam in the urine benzodiazepine assay by fluorescence polarization immunoassay (FPIA; Abbott TDx) in comparison with enzyme immunoassay (EIA; Syva EMIT d.a.u. benzodiazepine assay). alpha-OH triazolam at 300 ng/mL gave a response equivalent to the 200-ng/mL nordiazepam Abbott calibrator. In the EMIT assay, alpha-OH triazolam gave a response equivalent to the 300-ng/mL calibrator (Syva) at 100-200 ng/mL. Both immunoassays gave positive results in 9 out of 9 urine specimens collected from individuals receiving triazolam. Confirmation was performed by analyzing for alpha-OH triazolam after enzymatic hydrolysis and formation of a TMS derivative for GC/MS. All urine specimens were positive for alpha-OH triazolam. In conclusion, both the FPIA and EIA immunoassay screening assays are acceptable for detecting the presence of alpha-OH triazolam in the urine of patients receiving therapeutic doses of triazolam.

Simple and economical culture of Campylobacter jejuni and Campylobacter coli in CO2 in moist air

Strains of Campylobacter jejuni and C. coli representing the 18 serogroups (Lior) most commonly isolated from humans in Canada were grown on solid media in an atmosphere of 10% CO2 in moist air, 99% relative humidity. When the growth of all 18 serogroups on Mueller Hinton agar in a microaerobic atmosphere (5% O2, 10% CO2 and 85% N2) was compared with the growth of all 18 serogroups on the same media in 10% CO2 in moist air, colony sizes were significantly larger (p less than 0.05) for strains grown in 10% CO2 in moist air. No significant difference in colony numbers was seen between the two atmospheres. The addition of blood to the media significantly enhanced the growth of the campylobacters in both types of atmospheres (p less than 0.05). This simple CO2 atmosphere permitted the use of a common CO2 incubator thereby reducing the cost and difficulty of culturing these organisms.

Molecular discrimination of Campylobacter coli serogroup 20 biotype I (Lior) strains

Plasmid, protein and restriction endonuclease analysis (REA) profiles and multilocus enzyme electrophoresis were used to effect a molecular discrimination of twenty-seven Campylobacter coli serogroup 20, biotype 1 (Lior) strains. These strains were not outbreak-associated but were isolated from a number of different countries and different animal and environmental sources. Each of the techniques was able to discriminate, to various degrees, between the serogroup 20, biotype 1 strains. The choice of a particular technique depends to a large extent on the level of discrimination desired, the previous experiences of the investigator and on the laboratory facilities at hand. REA profiles demonstrated the greatest degree of discrimination between these strains. Plasmid and protein profiles could discriminate reasonably well. Multilocus enzyme electrophoresis (allozyme typing) and protein profiles may prove effective in subgrouping serogroup 20, biotype 1 strains.

Toxicological analysis of a fatal baclofen (Lioresal) ingestion

A fatality following ingestion of the drug baclofen (Lioresal) is described. Baclofen was identified in urine by gas chromatography/mass spectrometry. After derivatization with trinitrobenzene sulfonic acid, baclofen was quantitated in serum and urine by high-performance liquid chromatography. The concentration of baclofen was 17 mg/L in serum and 760 mg/L in urine collected approximately 12 h after the overdose. To our knowledge, this is only the second reported fatality involving a baclofen overdose. The previous case did not include quantitation of baclofen in any biological fluid.

Evaluation of the Abbott ADx and TDx serum benzodiazepine immunoassays for analysis of alprazolam

This study evaluated the Abbott ADx and TDx serum benzodiazepine assays for the analysis of alprazolam in serum. These systems were compared to the EMIT tox serum benzodiazepine assay and a gas chromatographic (GC) method. Six-point calibration curves (nordiazepam concentrations from 50-1,000 ng/mL) were stable on both instruments for at least 14 days. The precision of these assays was determined using three control serums containing 75,300, and 700 ng/mL of nordiazepam. On the ADx, within-run coefficients of variation (CV) for the three controls were 3.9, 3.1, and 2.8%, respectively. Between-run CVs were 2.8, 1.4, and 1.2% on the ADx. For the TDx, within-run CVs were 1.9, 1.4, and 2.6, and between-run CVs were 4.1, 1.3, and 1.9% for the three controls. Percent cross-reactivity of serum alprazolam calibrators (25-100 ng/mL) ranged from 77-88% on the ADx and 60-79% on the TDx. 99 serum specimens containing alprazolam were analyzed with the ADx, TDx, EMIT, and by gas chromatography-electron capture detection (sensitivity of 5 ng/mL). Overall, 48 of 99 specimens on the TDx, 43 of 99 on the ADx (both with a cutoff of 12 ng/mL), and 0 of 99 by EMIT (cutoff of 300 ng/mL) were positive. Of the specimens reading negative on the Abbott systems, 43 of 51 TDx results and 44 of 56 ADx results were obtained in specimens containing less than 25 ng/mL of alprazolam. For specimens with more than 25 ng/mL of alprazolam in serum (by GC), 8 specimens were negative on the TDx and 12 on the ADx.

Urinary screening for alprazolam and its major metabolites by the Abbott ADx and TDx analyzers with confirmation by GC/MS

Alprazolam is a short-acting triazolobenzodiazepine with anxiolytic and antidepressant properties. It has a half-life of 10-15 hours after multiple oral doses. Approximately 20% of an oral dose is excreted unchanged in the urine. The major urinary metabolites are alpha-OH alprazolam glucuronide and 3-HMB benzophenone glucuronide. The objective of this study was to characterize the reactivity of alprazolam and three metabolites in the Abbott ADx and TDx urinary benzodiazepine assays compared with the EMIT d.a.u. benzodiazepine assay. Alprazolam (at 300 ng/mL) gave an equivalent response as the 300 ng/mL low control (nordiazepam). alpha-OH alprazolam gave an equivalent response to this control between 300-500 ng/mL and 4-OH alprazolam between 500-1000 ng/mL. The 3-HMB benzophenone was not positive even at 10,000 ng/mL. The ADx screening assay was positive in 26 of 31 urine specimens collected from alprazolam-treated patients. All 31 of these specimens were confirmed positive for alpha-OH alprazolam by GC/MS after enzymatic hydrolysis and formation of a TMS derivative. For the TDx, 27 of 31 specimens were positive for benzodiazepines and all 31 were confirmed by GC/MS. All 5 of the negative ADx specimens and 4 of 5 TDx specimens contained 150-400 ng/mL of alpha-OH alprazolam. In conclusion, both the ADx and TDx urine benzodiazepine assays are acceptable screening assays for alprazolam use when the alpha-OH alprazolam concentration is greater than 400 ng/mL.

Urinary screening for midazolam and its major metabolites with the Abbott ADx and TDx analyzers and the EMIT d.a.u. benzodiazepine assay with confirmation by GC/MS

Midazolam is a short-acting 1,4-imidazole benzodiazepine with sedative-hypnotic, anxiolytic, and amnestic properties. It is administered orally for sleeping disorders and intravenously for sedation during surgery. This drug has a short half-life (1.5-3.5 h), with less than 1% of a midazolam dose being excreted unchanged. The major urinary metabolite is alpha-hydroxy midazolam glucuronide. The objective of this study was to characterize the reactivity of midazolam and its two major metabolites in the EMIT d.a.u. benzodiazepine assay and in the Abbott TDx and ADx urine benzodiazepine assays. Midazolam and alpha-OH midazolam gave an equivalent response to the EMIT low calibrator at 200 ng/mL. On both Abbott analyzers, midazolam and alpha-OH midazolam gave an equivalent net polarization at 500 ng/mL to the Abbott low control. All three screening assays were positive in all of 21 random urine specimens collected from midazolam-treated patients. Confirmation testing was performed by analyzing for alpha-OH midazolam after enzymatic hydrolysis and formation of a TMS derivative for GC/MS. All urine specimens were confirmed positive for alpha-OH midazolam. In conclusion, all three immunoassay screening assays are acceptable for detecting the presence of midazolam metabolites in urine.

Clinical toxicology of drugs used in the treatment of opiate dependency

Many aspects of the pharmacokinetics of methadone have been evaluated since 1970. Analytic techniques used to monitor urine and serum or plasma concentrations of methadone and its metabolites have improved with advances in chromatography and development of immunoassay techniques. On reviewing the literature on methadone since 1970, however, there were several recurring limitations of the experimental design in a large number of the studies reported. These include: 1. No appreciation for the effect of urinary pH on excretion of methadone 2. Small number of patients enrolled with inadequate control subjects 3. The effect of smoking cigarettes was not evaluated or adequately controlled 4. Urine collections were often obtained without supervision and correcting results to creatinine excretion 5. Blood specimens were generally not collected from 0-15 minutes after intravenous dosing 6. Incomplete excretion data (nonhydrolysis of glucuronide conjugates) in the urine 7. Most studies did not evaluate protein binding of methadone when attempting to correlate therapeutic control or failure with serum concentrations of methadone. In general, the literature supporting the use of naltrexone was more favorable than for methadone, buprenorphine, LAAM, and clonidine. The major limitation on the use of naltrexone, however, is the lack of incentive for the patient to keep taking the medication. If the use of naltrexone, LAAM, buprenorphine, or clonidine becomes widely available, robust analytic techniques must be developed for monitoring of these drugs, their metabolites, or both in the urine to verify patient compliance.

Once-daily ethosuximide in the treatment of absence epilepsy

Once-daily ethosuximide was used to treat 10 consecutive children with typical absence seizures. Three patients had gastrointestinal side effects which resolved when the same total daily dose was divided into 2 doses. Two other patients continued to have seizures on ethosuximide, whether given once or twice daily. Five patients had complete seizure control without adverse effects on once-daily ethosuximide.

Plasmid transfer and plasmid-mediated genetic exchange in Brucella abortus

Naturally-occurring plasmids and gene transfer mechanisms have not yet been reported in brucellae. Here we show that Brucella abortus is capable of maintaining and transferring the broad-host-range plasmids pTH10 (IncP), pSa (IncW) and R751 (IncP), and describe pTH10-mediated transfer of B. abortus chromosomal genes to Escherichia coli. All three plasmids transferred by conjugation from E. coli to B. abortus S19, and from B. abortus S19 to B. abortus 292 (biovar 4). They were stably maintained with no effect on biotyping characteristics. Plasmid pTH10 is a Tn1-containing derivative of RP4. It confers temperature-sensitive resistance to kanamycin, tetracycline and ampicillin to E. coli, but its tetracycline resistance and temperature sensitivity were poorly expressed in B. abortus. Plasmids pTH10 and pSa both transferred from B. abortus to E. coli DP50, a strain that is auxotrophic for diaminopimelic acid (DAP) Plasmid pTH10 (but not pSa) mobilized Brucella chromosomal gene(s) for DAP synthesis to DP50, yielding non-DAP-requiring (NDR) transconjugants. Neither plasmid transferred the NDR marker from their original E. coli host strains, nor did pTH10 transfer it from NDR transconjugants. Escherichia coli NDR transconjugant EP8.11 was cured of pTH10 by passage at the nonpermissive temperature, but retained the NDR marker and the Tn1-encoded resistance to ampicillin, indicating Tn1-mediated integration of Brucella chromosomal DNA into the E. coli chromosome.