Removal of Remdesivir's Metabolite GS-441524 by Hemodialysis in a Double Lung Transplant Recipient with COVID-19.

Remdesivir has reported efficacy against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in vitro and in vivo Drug-drug interactions limit therapeutic options in transplant patients. Remdesivir and its metabolite GS-441524 are excreted principally in urine. In intensive care unit (ICU) settings, in which multiple-organ dysfunctions can occur rapidly, hemodialysis may be a viable option for maintaining remdesivir treatment, while improving tolerance, by removing both remdesivir's metabolite (GS-441524) and sulfobutylether ß-cyclodextrin sodium (SEBCD). Additional studies may prove informative, particularly in the evaluations of therapeutic options for coronavirus disease 2019 (COVID-19).

Urinary Melamine Levels and Progression of CKD.

BACKGROUND AND OBJECTIVES: CKD is a global public health problem. Some cross-sectional studies have associated environmental melamine exposure with kidney diseases, but evidence is limited. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: We conducted this prospective cohort study to enroll patients with eGFR≥30 ml/min per 1.73 m2 in 2006-2010. Urinary corrected melamine levels (ratio of urinary melamine to urinary creatinine) were measured by liquid chromatography/tandem mass spectrometry at enrollment. Kidney outcomes included doubling of serum creatinine levels, eGFR decline >3 ml/min per 1.73 m2 per year, and 30% decline in eGFR in the first 2 years. Subjects were followed until targeted kidney outcomes, cancer, death, last contact, or the end of observation in December 2016. RESULTS: In a total of 293 subjects, the median urinary corrected melamine level was 0.97 (interquartile range, 0.43-2.08) µg/mmol. Over a median follow-up period of 7.0 years, serum creatinine levels doubled in 80 subjects (27%). Subjects in the highest tertile of urinary melamine level 12.70 µg/mmol) had a 2.30 (95% confidence interval, 1.25 to 4.23; P<0.01) hazard risk for doubling of serum creatinine compared with those in the lowest tertile (0.02-0.58 µg/mmol). Similar significant dose-response results were found in eGFR decline >3 ml/min per 1.73 m2 per year and 30% decline in eGFR in the first 2 years. CONCLUSIONS: Urinary melamine level is significantly associated with kidney function deterioration in patients with early-stage CKD.

Absorption, distribution, metabolism and excretion of an isocitrate dehydrogenase-2 inhibitor enasidenib in rats and humans.

1. The absorption, distribution, metabolism and excretion of enasidenib were studied following a single oral dose of [14C]enasidenib to rats (10 mg/kg; 100 µCi/kg) and healthy volunteers (100 mg; 318 nCi). 2. Enasidenib was readily absorbed, extensively metabolized and primarily eliminated via the hepatobiliary pathway. Enasidenib-derived radioactivity was widely distributed in rats. Excretion of radioactivity was approximately 95-99% of the dose from rats in 168 h post-dose and 82.4% from human volunteers in 504 h post-dose. In rat bile, approximately 35-42% of the administered dose was recovered, with less than 5% of the dose excreted as the parent drug. Renal elimination was a minor pathway, with <12% of the dose excreted in rat urine and <10% of the dose excreted in human urine. 3. Enasidenib was the prominent radioactive component in rat and human systemic circulation. Enasidenib was extensively metabolized in rats and human volunteers through N-dealkylation, oxidation, direct glucuronidation and combinations of these pathways. Glucuronidation was the major metabolic pathway in rats while N-dealkylation was the prominent metabolic pathway in human volunteers. All human metabolites were detected in rats.

Development and validation of a UPLC-MS/MS method for simultaneous determination of fotagliptin and its two major metabolites in human plasma and urine.

AIM: Fotagliptin is a novel dipeptidyl peptidase IV inhibitor under clinical development for the treatment of Type II diabetes mellitus. The objective of this study was to develop and validate a specific and sensitive ultra-performance liquid chromatography (UPLC)-MS/MS method for simultaneous determination of fotagliptin and its two major metabolites in human plasma and urine. Methodology & results: After being pretreated using an automatized procedure, the plasma and urine samples were separated and detected using a UPLC-ESI-MS/MS method, which was validated following the international guidelines. CONCLUSION: A selective and sensitive UPLC-MS/MS method was first developed and validated for quantifying fotagliptin and its metabolite in human plasma and urine. The method was successfully applied to support the clinical study of fotagliptin in Chinese healthy subjects.

Melamine-contaminated milk formula and its impact on children.

The melamine contaminated milk powder contamination scandal occurred in China in 2008. Its main consequences so far have been urinary stone formation in children with associated renal damage and increased child mortality. Eight years have passed, but food safety issues still remain of concern in the daily lives of millions of Chinese. Vigilance is required to ensure no recurrence of such food safety problems. Ongoing studies focus on the early detection of food industry malpractice, mechanisms whereby these toxic substances induce disease and how its advent may be prevented and better managed. Melamine undergoes renal excretion, but is metabolized slowly and excreted largely unchanged in the urine. Urinary melamine measurement may provide a rapid and inexpensive way to identify exposure to melamine adulterated food items. Although most patients with melaminerelated urinary stones (MUS) have been responsive to conservative treatment, longer time follow-up is needed to assess chronic effects. Aside from MUS, melamine is a recognized carcinogen and can induce urinary tract tumours. Very little is known about the effects of excessive exposure to melamine contaminated milk powder in infants on growth, adolescent and adult health, although short-term effects have become apparent during the scandal.

2,7-Disubstituted-pyrrolotriazine kinase inhibitors with an unusually high degree of reactive metabolite formation.

There are numerous published studies establishing a link between reactive metabolite formation and toxicity of various drugs. Although the correlation between idiosyncratic reactions and reactive metabolite formation is not 1:1, the association between the two is such that many pharmaceutical companies now monitor for reactive metabolites as a standard part of drug candidate testing and selection. The most common method involves in vitro human microsomal incubations in the presence of a thiol trapping agent, such as glutathione (GSH), followed by LC/MS analysis. In this study, we describe several 2,7-disubstituted-pyrrolotriazine analogues that are extremely potent reactive metabolite precursors. Utilizing a UPLC/UV/MS method, unprecedented levels of GSH adducts were measured that are 5-10 times higher than previously reported for high reactive metabolite-forming compounds such as clozapine and troglitazone.

Low exposure to melamine increases the risk of urolithiasis in adults.

Melamine, a widely used chemical found in many products in daily use, became a public health concern due to melamine-associated urinary stone formation in children. In adults, it is still unknown whether low-dose melamine exposure may also cause urolithiasis. To address this question, we studied 211 Taiwanese patients diagnosed with calcium urolithiasis and 211 age- and gender-matched controls. All patients completed a detailed questionnaire and provided blood and urine samples for biochemical analysis. Urinary melamine concentrations were measured by triple-quadrupole liquid chromatography tandem mass spectrometry. Compared with those whose urinary melamine levels were below the detection limit of the method, patients with urinary melamine levels of up to 3.11 ng/ml and those with levels of ≥3.12 ng/ml had 3.01- and 7.64-fold increased risk, respectively, of calcium urolithiasis after adjusting for educational level, fluid intake, cigarette smoking, betel quid chewing, alcohol drinking, urinary uric acid, calcium, creatinine, and estimated creatinine clearance rate. The population attributable risk of calcium urolithiasis averaged 50% when melamine was detected in the urine, after considering other covariates. MALDI-TOF mass spectrometry detected melamine in the stones of nine representative patients who had measurable urinary melamine levels. Thus, low-dose melamine exposure can play an important role in calcium urolithiasis in Taiwanese adults.

Urinary biomarkers of prenatal atrazine exposure and adverse birth outcomes in the PELAGIE birth cohort.

BACKGROUND: Despite evidence of atrazine toxicity in developing organisms from experimental studies, few studies--and fewer epidemiologic investigations--have examined the potential effects of prenatal exposure. OBJECTIVES: We assessed the association between adverse birth outcomes and urinary biomarkers of prenatal atrazine exposure, while taking into account exposures to other herbicides used on corn crops (simazine, alachlor, metolachlor, and acetochlor). METHODS: This study used a case-cohort design nested in a prospective birth cohort conducted in the Brittany region of France from 2002 through 2006. We collected maternal urine samples to examine pesticide exposure biomarkers before the 19th week of gestation. RESULTS: We found quantifiable levels of atrazine or atrazine mercapturate in urine samples from 5.5% of 579 pregnant women, and dealkylated and identified hydroxylated triazine metabolites in 20% and 40% of samples, respectively. The presence versus absence of quantifiable levels of atrazine or a specific atrazine metabolite was associated with fetal growth restriction [odds ratio (OR) = 1.5; 95% confidence interval (CI), 1.0-2.2] and small head circumference for sex and gestational age (OR = 1.7; 95% CI, 1.0-2.7). Associations with major congenital anomalies were not evident with atrazine or its specific metabolites. Head circumference was inversely associated with the presence of quantifiable urinary metolachlor. CONCLUSIONS: This study is the first to assess associations of birth outcomes with multiple urinary biomarkers of exposure to triazine and chloroacetanilide herbicides. Evidence of associations with adverse birth outcomes raises particular concerns for countries where atrazine is still in use.

Lamotrigine and its N2-glucuronide during pregnancy: the significance of renal clearance and estradiol.

PURPOSE: To investigate the physiological mechanisms behind the pronounced decline of lamotrigine (LTG) serum concentrations during pregnancy. METHODS: Serum and urine concentrations of LTG and its main metabolite, LTG-N2-glucuronide (LTG-GLUC), were measured monthly in 21 pregnancies of 19 women using LTG. Simultaneously, a panel of biochemical variables was monitored to evaluate liver and kidney function and possible hemodilution effects. Pharmacokinetic parameters were calculated once at baseline and once in gestational month 8. RESULTS: Initially, LTG and LTG-GLUC serum concentrations fell simultaneously by 27% and 38%, respectively (gestational month 2). Subsequently, the ratio of the LTG-GLUC/LTG serum concentrations increased gradually, correlating strongly with rising serum estradiol concentrations. In gestational month 8, the ratio was 164% higher than at baseline. At that time, LTG total clearance had increased by 118%, and the amount of unchanged LTG in urine had dropped by 40% while the amount of LTG-GLUC had increased by a corresponding 37%. CONCLUSIONS: The simultaneous decline of LTG and LTG-GLUC serum concentrations in early pregnancy suggests that in this phase, increased renal blood flow is the major cause. After gestational month 2, estradiol-induced glucuronidation of LTG becomes more important, leading to a further fall of LTG serum concentrations and a gradual rise of the LTG-GLUC/LTG-ratio through the remaining pregnancy. An expanded volume of distribution may also contribute to reduced LTG serum concentrations in pregnancy.

Metabolism and disposition of [14C]brivanib alaninate after oral administration to rats, monkeys, and humans.

Brivanib [(R)-1-(4-(4-fluoro-2-methyl-1H-indol-5-yloxy)-5-methylpyrrolo[1,2,4]triazin-6-yloxy)propan-2-ol, BMS-540215] is a potent and selective dual inhibitor of vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF) signaling pathways. Its alanine prodrug, brivanib alaninate [(1R,2S)-2-aminopropionic acid 2-[4-(4-fluoro-2-methyl-1H-indol-5-yloxy)-5-methylpyrrolo[2,1-f][1,2,4]triazin-6-yloxy]-1-methylethyl ester, BMS-582664], is currently under development as an oral agent for the treatment of cancer. This study describes the in vivo biotransformation of brivanib after a single oral dose of [(14)C]brivanib alaninate to intact rats, bile duct-cannulated (BDC) rats, intact monkeys, BDC monkeys, and humans. Fecal excretion was the primary route of elimination of drug-derived radioactivity in animals and humans. In BDC rats and monkeys, the majority of radioactivity was excreted in bile. Brivanib alaninate was rapidly and completely converted via hydrolysis to brivanib in vivo. The area under the curve from zero to infinity of brivanib accounted for 14.2 to 54.3% of circulating radioactivity in plasma in animals and humans, suggesting that metabolites contributed significantly to the total drug-related radioactivity. In plasma from animals and humans, brivanib was a prominent circulating component. All the metabolites that humans were exposed to were also present in toxicological species. On the basis of metabolite exposure and activity against VEGF and FGF receptors of the prominent human circulating metabolites, only brivanib is expected to contribute to the pharmacological effects in humans. Unchanged brivanib was not detected in urine or bile samples, suggesting that metabolic clearance was the primary route of elimination. The primary metabolic pathways were oxidative and conjugative metabolism of brivanib.

Metabolism, excretion, and pharmacokinetics of oral brivanib in patients with advanced or metastatic solid tumors.

The goal of this study was to evaluate the pharmacokinetics, mass balance, metabolism, routes and extent of elimination, and safety of a single oral dose of (14)C-labeled brivanib alaninate and the safety and tolerability of brivanib after multiple doses in patients with advanced or metastatic solid tumors. This was a two-part, single-center, open-label, single oral-dose (part A) followed by multiple-dose (part B) study in patients with advanced or metastatic solid tumors. In part A, patients received a single dose of [(14)C]brivanib alaninate and in part B patients received 800 mg of nonradiolabeled brivanib alaninate every day. Four patients (two white, two black: two with non-small-cell lung cancer, one with ovarian cancer, and one with renal cell carcinoma) were treated in both parts. The median time to reach the maximal plasma concentration of brivanib was 1 h, geometric mean maximal plasma concentration was 6146 ng/ml, mean terminal half-life was 13.8 h, and geometric mean apparent oral clearance was 14.7 l/h. After a single oral dose of [(14)C]brivanib alaninate, 12.2 and 81.5% of administered radioactivity was recovered in urine and feces, respectively. Brivanib alaninate was completely converted to the active moiety, brivanib, and the predominant route of elimination was fecal. Renal excretion of unchanged brivanib was minimal. Brivanib was well tolerated; fatigue was the most frequent adverse event occurring in all patients and the most frequent treatment-related adverse event in three (75%). The best clinical response in one patient was stable disease; the other three had progressive disease. Brivanib alaninate was rapidly absorbed and extensively metabolized after a single 800-mg oral dose; the majority of drug-related radioactivity was excreted in feces.

Metabolism and disposition of [14C]BMS-690514, an ErbB/vascular endothelial growth factor receptor inhibitor, after oral administration to humans.

(3R,4R)-4-Amino-1-((4-((3-methoxyphenyl)amino)pyrrolo[2,1-f][1,2,4]triazin-5-yl)methyl)-3-piperidinol (BMS-690514), an oral selective inhibitor of human epidermal growth factor receptors 1 (or epidermal growth factor receptor), 2, and 4, and vascular endothelial growth factor receptors 1, 2, and 3, is being developed as a treatment for patients with non-small-cell lung cancer and metastatic breast cancer. The disposition of [(14)C]BMS-690514 was investigated in nine healthy male subjects (group 1, n = 6; group 2, n = 3) after oral administration of a 200-mg dose. Urine, feces, and plasma were collected from all subjects for up to 12 days postdose. In group 2 subjects, bile was collected from 3 to 8 h postdose. Across groups, approximately 50 and 34% of administered radioactivity was recovered in the feces and urine, respectively. An additional 16% was recovered in the bile of group 2 subjects. Less than 28% of the dose was recovered as parent drug in the combined excreta, suggesting that BMS-690514 was highly metabolized. BMS-690514 was rapidly absorbed (median time of maximum observed concentration 0.5 h) with the absorbed fraction estimated to be approximately 50 to 68%. BMS-690514 represented ≤7.9% of the area under the concentration-time curve from time 0 extrapolated to infinite time of plasma radioactivity, indicating that the majority of the circulating radioactivity was from metabolites. BMS-690514 was metabolized via multiple oxidation reactions and direct glucuronidation. Circulating metabolites included a hydroxylated rearrangement product (M1), a direct ether glucuronide (M6), and multiple secondary glucuronide conjugates. None of these metabolites is expected to contribute to the pharmacology of BMS-690514. In summary, BMS-690514 was well absorbed and extensively metabolized via multiple metabolic pathways in humans, with excretion of drug-related radioactivity in both bile and urine.

A gas chromatography/mass spectrometry method for the determination of sildenafil, vardenafil and tadalafil and their metabolites in human urine.

Sildenafil (SDF), vardenafil (VDF) and tadalafil (TDF) are phosphodiesterase type 5 enzyme inhibitors (PDE5Is), used in the treatment of erectile disorders and to improve breathing efficiency in pulmonary hypertension. The increasing incidence of their use among young athletes has drawn the attention of the anti-doping authorities to the possible abuse of PDE5Is by athletes due to their pharmacological activities. This paper describes a method for the determination in urine of PDE5Is and their metabolites by gas chromatography/mass spectrometry (GC/MS) after liquid/liquid extraction of the analytes from urine and derivatisation to obtain trimethylsilyl derivatives. The metabolic profile was studied on real samples collected from subjects taking PDE5Is (Viagra, Levitra or Cialis); the main urinary metabolites were identified and their MS fragmentation characterized. The sample pre-treatment and GC/MS conditions for the detection of the metabolites have been optimised. A method for their preliminary screening and subsequent confirmation is described that takes into account the general requirements of a routine doping analysis to be used for the screening of large numbers of samples. The main metabolites identified can be included in a general purpose screening method and all the metabolites in a more specific confirmation method. The method developed has been applied for the screening of PDE5Is in 5000 urine samples. Based on the obtained results, the proposed method appears to be of practical use in analytical and forensic toxicology, including doping analysis.

Liquid-liquid-solid microextraction based on membrane-protected molecularly imprinted polymer fiber for trace analysis of triazines in complex aqueous samples.

A novel liquid-liquid-solid microextraction (LLSME) technique based on porous membrane-protected molecularly imprinted polymer (MIP)-coated silica fiber has been developed. In this technique, a MIP-coated silica fiber was protected with a length of porous polypropylene hollow fiber membrane which was filled with water-immiscible organic phase. Subsequently the whole device was immersed into aqueous sample for extraction. The LLSME technique was a three-phase microextraction approach. The target analytes were firstly extracted from the aqueous sample through a few microliters of organic phase residing in the pores and lumen of the membrane, and were then finally extracted onto the MIP fiber. A terbutylazine MIP-coated silica fiber was adopted as an example to demonstrate the feasibility of the novel LLSME method. The extraction parameters such as the organic solvent, extraction and desorption time were investigated. Comparison of the LLSME technique was made with molecularly imprinted polymer based solid-phase microextraction (MIP-SPME) and hollow fiber membrane-based liquid-phase microextraction (HF-LPME), respectively. The LLSME, integrating the advantages of high selectivity of MIP-SPME and enrichment and sample cleanup capability of the HF-LPME into a single device, is a promising sample preparation method for complex samples. Moreover, the new technique overcomes the problem of disturbance from water when the MIP-SPME fiber was exposed directly to aqueous samples. Applications to analysis of triazine herbicides in sludge water, watermelon, milk and urine samples were evaluated to access the real sample application of the LLSME method by coupling with high-performance liquid chromatography (HPLC). Low limits of detection (0.006-0.02 microg L(-1)), satisfactory recoveries and good repeatability for real sample (RSD 1.2-9.6%, n = 5) were obtained. The method was demonstrated to be a fast, selective and sensitive pretreatment method for trace analysis of triazines in complex aqueous samples.

[Determination of atrazine and its metabolites in human urines using gas chromatography].

Atrazine (ATZ) was widely used to control broadleaf weeds. Numerous animal experiments have proved that atrazine is a suspicious endocrine disruptor. Thus, further development of the ability to estimate low-dose human exposure to atrazine is requested in epidemiologic studies to correlate the toxicological effects associated with the concentrations of ATZ and its metabolites in human body. A method for detecting ATZ and its metabolites (deethylatrazine (DEA), deisopropylatrazine (DIA), deethyldeisopropylatrazine (DEDIA)) in human urines using gas chromatography was established. A urine sample was extracted by ethyl acetate, and purified using a Florisil column. Final concentrated extract was analyzed by a gas chromatograph-electron capture detector. The conditions of this method were optimized. The limits of detection were 0. 002 5 mg/L for DEDIA, 0. 005 mg/L for DEA, DIA and ATZ. The linear ranges were from 0.2 to 8 ng for all analytes. The atrazine concentrations in urine samples of the workers collected from an atrazine plant were determined by this method. The concentration ranges were 0.003 -0.301 mg/L for DEDIA, 0.005 -0.011 mg/L for DEA, 0.006 -0.276 mg/L for DIA, and 0.005 -0.012 mg/L for ATZ.

Metabolism of lamotrigine to a reactive arene oxide intermediate.

Lamotrigine [3,5-diamino-6-(2,3-dichlorophenyl)-1,2,4-triazine] is an antiepileptic drug associated with hypersensitivity reactions which are thought to be an immunological response to metabolically generated drug-protein adducts. The o-dichlorophenyl moiety is a potential site for bioactivation of the drug to an arene oxide. The metabolites of [(14)C]lamotrigine (78 micromol/kg, iv) in adult male Wistar rats were characterized with particular reference to thioether derivatives of an epoxide intermediate. Biliary recovery of radioactivity from anesthetized and cannulated animals was 7.3 +/- 3.0% (mean +/- SD, n = 4) of the dose over 4 h; 5.5 +/- 0.5% was recovered in bladder urine after 4 h. Bile contained [(14)C]lamotrigine (1.4 +/- 0.3%), a glutathione adduct of [(14)C]dihydrohydroxylamotrigine (1.8 +/- 0.3%), i.e., an adduct of an arene oxide, and the glutathione (1.5 +/- 0.7%), cysteinylglycine (1.9 +/- 0.5%), and N-acetylcysteine (0.4 +/- 0.2%) adducts of [(14)C]lamotrigine. Formation of the thioether metabolites was partially blocked by the cytochrome P450 inhibitor, ketoconazole. Urine contained [(14)C]lamotrigine (4.5 +/- 0.5%) and [(14)C]lamotrigine N-oxide (0.9 +/- 0.2%). The radiolabeled material in skin (15.6 +/- 1.4%) was almost entirely [(14)C]lamotrigine. Isolated rat hepatocytes achieved a low rate of turnover to the glutathione adduct and N-oxide. However, neither rat nor human liver microsomes catalyzed NADPH-dependent irreversible binding. Lamotrigine can be bioactivated to an arene oxide by rat hepatocytes in the absence of a major competing pathway such as N-glucuronidation. Inhibition of N-glucuronidation has been associated with an increased risk of skin reactions in patients.

Chronic toxicity and oncogenicity bioassay in rats with the chloro-s-triazine herbicide cyanazine.

Cyanazine is a member of the chloro-s-triazine class of herbicides. Other triazine herbicides have been shown to induce mammary-gland tumors in rats, although the response is unique to the Sprague-Dawley strain. Cyanazine is nongenotoxic. The present study was conducted to evaluate the chronic toxicity and oncogenic potential of cyanazine. Groups of 62 male and female rats were fed diets containing cyanazine at concentrations of 1, 5, 25, or 50 ppm for up to 2 yr. Mean body weight and body weight gain of male and female rats of the 25- and 50-ppm groups were significantly reduced over the course of the study. Food consumption and food efficiency were also reduced in these groups. Survival was not adversely affected in the treatment groups compared to controls. A significant increase in the incidence of masses of the inguinal region was noted among female rats of the 50-ppm group. These masses were correlated with a significant increase in the incidence of female rats with mammary-gland adenocarcinomas and carcinosarcomas. The incidence of rats with malignant mammary-gland tumors was elevated in the 5-, 25-, and 50-ppm groups, although the incidence within the 5-ppm group was within historical controls. There were no other toxicologically significant observations with respect to ophthalmological, clinical laboratory, or pathological evaluations. Under the conditions of this study, the no-observed-adverse-effect level was 5 ppm. Research into the mechanism of action suggests these mammary tumors are mediated through a prolactin mechanism that is thought to be of low relevance to humans.

Pharmacokinetics and bioreductive metabolism of the novel benzotriazine di-N-oxide hypoxic cell cytotoxin tirapazamine (WIN 59075; SR 4233; NSC 130181) in mice.

The novel benzotriazine di-N-oxide SR 4233 (3-amino-1,2,4-benzotriazine-1,4-di-N-oxide) shows high selective cytotoxicity toward hypoxic tumor cells. We investigated its pharmacokinetics and bioreductive metabolism in mouse plasma, brain, liver and tumor in vivo and also tumor metabolism in vitro. Plasma elimination T1/2 increased slightly with dose, and metabolite kinetics were dose-dependent. Peak concentration and area under the curve0-infinity increased linearly with dose from 0.1 to 0.3 mmol kg-1 i.v. After 0.2 mmol kg-1 i.v., elimination was biphasic (T1/2 alpha < 2 min; T1/2 beta, 26.5 min). Peak plasma concentration and area under the curve0-infinity were 26 and 13.6 micrograms ml-1 hr, respectively. Peak plasma concentration for the two-electron reduction product SR 4317 (3-amino-1,2,4-benzotriazine-1-oxide) was 7 to 9 micrograms ml-1 and for the four-electron reduction product SR 4330 (3-amino-1,2,4-benzotriazine) peak plasma concentration was 0.5 to 1.0 micrograms ml-1. Identical results were obtained after i.p. administration. Oral dosing gave lower peak plasma drug concentrations (2-3 micrograms ml-1) but reasonable bioavailability (75%). SR 4233 underwent extensive bioreduction in KHT tumors. Tumor/plasma ratios (percentages) for SR 4233 were 32% compared to 174 (SR 4317) and 196% (SR 4330), respectively. Similar SR 4233 tissue/plasma percentages were obtained in RIF-1 and 16C tumors, but EMT6 tumors were markedly lower at 7%. Reduction also occurred with tumor homogenates in vitro (KHT = EMT6 > RIF-1). Conversion to SR 4317 and SR 4330 was more extensive in liver, with tissue/plasma percentages between 50 to 220 and 500 to 1800%, respectively. The brain showed a similar pattern to tumors. Urinary recoveries (0-8 hr) were low at 4.5% for SR 4233 and 0.4% for the reduced metabolites. A further 30% occurred as a glucuronide. Concentrations of SR 4233 required for effective in vitro cytotoxicity are achieved in vivo, and extensive bioreductive metabolism occurs in tumor and normal tissues.

Rapid isolation with Sep-Pak C18 cartridges and capillary gas chromatography of triazine herbicides in human body fluids.

A simple and rapid method, for the isolation of eight triazine herbicides from human serum and urine, using Sep-Pak C18 cartridges is presented. After mixing with distilled water, serum and urine samples containing the herbicides, were loaded on Sep-Pak C18 cartridges and eluted with either chloroform only or chloroform/methanol (9:1). The herbicides were detected by capillary gas chromatography with both flame ionization detection (FID) and nitrogen-phosphorus detection (NPD). Separation of eight triazine herbicides from each other and from impurities was generally satisfactory with the use of a non-polar DB-1 capillary column. Recovery of most compounds was excellent for both chloroform and chloroform/methanol (9:1) as elution solvents. Backgrounds were cleaner and evaporation time was shorter for the chloroform only than for the chloroform/methanol (9:1). The NPD gave sensitivity more than 10-20 times higher than that of FID.