Concentrations of N-methyl-2-pyrrolidone (NMP) and its metabolites in plasma and urine following oral administration of NMP to rats

Workplace environmental exposure level guide: n-Methyl-2-pyrrolidone

n-Methyl-2-pyrrolidone (NMP) is a widely used solvent with a mild amine-like odor that can exist in a vapor or aerosol at moderate temperatures. In humans, NMP was reported to induce weak and transient eye irritation and headache. NMP was not a dermal sensitizer and has a low acute toxicity via oral, dermal, and inhalation routes. NMP was not genotoxic/mutagenic in a battery of in vitro and in vivo studies. Furthermore, NMP was not carcinogenic in rats although species-specific liver tumors were identified in mice. Chronic studies in the rat provided a NOAEL of 10 ppm (40 mg/m³) causing only minor effects in males (slightly reduced mean body weight) at 100 ppm (400 mg/m³). Developmental toxicity was considered the critical endpoint (decreased fetal body weights at non-maternally toxic doses). Benchmark dose and PBPK models were utilized to derive an internal dose of 350-470 mg·h/L as a NOAEL for this response and a human equivalent air concentration of 350-490 ppm. With the application of adjustment factors, an 8-h time-weighted average WEEL value of 15 ppm (60 mg/m³) was derived and is expected to provide a significant margin of safety against any potential adverse health effects in workers. To address the potential for respiratory irritation, a short-term exposure level of 30 ppm (120 mg/m³) was derived, and a skin notation is assigned because of the contribution of dermal absorption to the systemic toxicity of NMP.

Comparison of N-methyl-2-pyrrolidone (NMP) and the "date rape" drug GHB: behavioral toxicology in the mouse model

N-methyl-2-pyrrolidone (NMP) and γ-hydroxybutyrate acid (GHB) are synthetic solvents detected in the recreational drug market. GHB has sedative/hypnotic properties and is used for criminal purposes to compromise reaction ability and commit drug-facilitated sexual assaults and other crimes. NMP is a strong solubilizing solvent that has been used alone or mixed with GHB in case of abuse and robberies. The aim of this experimental study is to compare the acute pharmaco-toxicological effects of NMP and GHB on neurological signs (myoclonia, convulsions), sensorimotor (visual, acoustic, and overall tactile) responses, righting reflex, thermoregulation, and motor activity (bar, drag, and accelerod test) in CD-1 male mice. Moreover, since cardiorespiratory depression is one of the main adverse effects related to GHB intake, we investigated the effect of NMP and GHB on cardiorespiratory changes (heart rate, breath rate, oxygen saturation, and pulse distension) in mice. The present study demonstrates that NMP inhibited sensorimotor and motor responses and induced cardiorespiratory depression, with a lower potency and efficacy compared to GHB. These results suggest that NMP can hardly be used alone as a substance to perpetrate sexual assault or robberies.

Palladium Catalyst Recycling for Heck-Cassar-Sonogashira Cross-Coupling Reactions in Green Solvent/Base Blend

The identification of a green, versatile, user-friendly, and efficient methodology is necessary to facilitate the use of Heck-Cassar-Sonogashira (HCS) cross-coupling reaction in drug discovery and industrial production in the pharmaceutical segment. The Heck-Cassar and Sonogashira protocols, using N-hydroxyethylpyrrolidone (HEP)/water/N,N,N',N'-tetramethyl guanidine (TMG) as green solvent/base mixture and sulfonated phosphine ligands, allowed to recycle the catalyst, always guaranteeing high yields and fast conversion under mild conditions, with aryl iodides, bromides, and triflates. No catalyst leakage or metal contamination of the final product were observed during the HCS recycling. To our knowledge, a turnover number (TON) up to 2375, a turnover frequency (TOF) of 158 h-1 , and a process mass intensity (PMI) around 7 that decreased around 3 after solvent, base, and palladium recovery, represent one of the best results to date using a sustainable protocol. The Heck-Cassar protocol using sSPhos was successfully applied to the telescoped synthesis of Erlotinib (TON: 1380; TOF: 46 h-1 ).

Toxicokinetics of N-ethyl-2-pyrrolidone and its metabolites in blood, urine and amniotic fluid of rats after oral administration

The toxicokinetics of N-ethyl-2-pyrrolidone (NEP), an embryotoxic organic solvent, has been studied in Sprague-Dawley rats after oral exposure. NEP and its metabolites 5-hydroxy-N-ethyl-2-pyrrolidone (5-HNEP) and 2-hydroxy-N-ethylsuccinimide (2-HESI) were measured in plasma of pregnant and non-pregnant rats, and fetuses after NEP administration by gavage for 14 consecutive days at 50 mg/kg/day, and in plasma of non-pregnant rats after a single NEP administration. Additionally, amniotic fluid and 24-h urine samples of the pregnant rats were analyzed for NEP metabolites. Furthermore, 24-h urine samples from a repeated dose 28-day oral toxicity study in female (non-pregnant) and male rats administered developmentally non-toxic (0, 5, and 50 mg/kg/day) or toxic (250 mg/kg/day) doses of NEP were analyzed. Median peak plasma concentrations in non-pregnant rats after a single dose and repeated doses were 551 and 611 (NEP), 182 and 158 (5-HNEP), and 63.8 and 108 µmol/L (2-HESI), respectively; whereas in pregnant rats and fetuses 653 and 619 (NEP), 80.5 and 91.7 (5-HNEP) and 77.3 and 45.7 µmol/L (2-HESI) were detected. Times to reach maximum plasma concentrations for NEP, 5-HNEP, and 2-HESI were 1, 4, and 8 h, respectively, and were comparable to N-methyl-2-pyrrolidone (NMP) and its corresponding metabolites. In pregnant rats, plasma elimination of NEP and metabolite formation/elimination was much slower compared to non-pregnant rats and efficient placental transfer of NEP was observed. Our data, overall, suggest differences in the toxicokinetics of chemicals between pregnant and non-pregnant rats which need to be addressed in risk assessment, specifically when assessing developmental toxicants such as NEP.

Quantification of six potential unspecific human biomarkers of 1-vinyl-2-pyrrolidone exposure in Sprague-Dawley rat urine using gas chromatography coupled with triple mass spectrometry

RATIONALE

The monomer 1-vinyl-2-pyrrolidone (VP) is a substance with excellent solvent features. It is used in a wide variety of pharmaceutical, cosmetic, food industrial or technical applications and produced on an industrial scale. Since VP has caused adenocarcinoma of the nasal cavity and liver cell carcinoma in long-term experiments with rats, a human biomarker would be appreciated for risk assessment.

METHODS

A sensitive analytical electron ionization gas chromatography/tandem mass spectrometry (GC/MS/MS) method for the determination of six possible biomarkers for VP in urine was established and validated. Two isotope-labeled internal standards (ISTD) were used for quantification. A simple and easy to use freeze-drying step was performed prior to derivatization with N-tert-butyldimethylsilyl-N-methyltrifluoracetamide (MTBSTFA) and following sample extraction for cleanup purposes.

RESULTS

A calibration curve with six calibration standards ranging from 50 μg/L to 2000 μg/L (10-fold higher for H-OPAA) in urine was prepared. Validation results were satisfactory with recoveries ranging from 88.2 to 110.2 % with two exceptions for the lowest quality control for two substances without ISTD (126.4 % and 139.3 %). Three of the substances could be identified as VP metabolites in an exposure study with Sprague-Dawley (SD) rats.

CONCLUSIONS

A quick and easy to use method has been established for six target molecules investigated for a better understanding of the metabolism of VP. Two of three substances identified as metabolites of VP could serve as a nonspecific human biomarker for VP exposure as shown with an excerpt of an exposure study performed in SD rats.

Metabolism of N-Methyl-2-Pyrrolidone in Honey Bee Adults and Larvae: Exploring Age Related Differences in Toxic Effects

In chronic feeding assays, the common agrochemical inert formulant N-methyl-2-pyrrolidone (NMP) is at least 20 times more toxic to honey bee larvae than to adults, but the underlying cause of this difference is unknown. In other taxa, NMP is primarily detoxified via a cytochrome P450 mediated pathway. Using a LC-MS method, putative cytochrome P450 metabolites of NMP were identified and quantified in adults and larvae following chronic exposure to NMP. Major differences in the identities and quantities of the generated metabolites were observed between adults and larvae. One major difference was the higher percentage of the administered NMP recovered as the parent compound in larvae compared to adults. To further explore the apparent difference in metabolic capacity, a spectrofluorometric method was used to compare general cytochrome P450 enzyme activity by monitoring the transformation of a 7-ethoxycoumarin substrate. Higher microsomal levels of 7-ethoxycoumarin-O-deethylase activity in adult fat bodies suggests that the higher percentage of unmetabolized NMP in larvae relative to adults may be due to lower cytochrome P450 enzyme activity in fat bodies. Taken together, these results suggest that larvae may be less able to detoxify xenobiotics encountered in diet than adults, and these findings will help inform future risk assessment.

Field Residues and Effects of the Insect Growth Regulator Novaluron and Its Major Co-Formulant N-Methyl-2-Pyrrolidone on Honey Bee Reproduction and Development

Owing to the recent declines in honey bee (Apis mellifera L.) populations, there is a need for field and laboratory studies to investigate threats to pollinator health. This study examines the hypothesis that the organophosphate alternative, Rimon 0.83EC, can have consequences to honey bee health by combining newly acquired field residue data, laboratory bioassays, and colony level feeding studies. Following label rate applications of Rimon 0.83EC to apple trees, average residue concentrations of the active ingredient, novaluron, were found to be 3.38 ppm in tree-collected pollen. Residues of the major co-formulant in Rimon 0.83EC, N-methyl-2-pyrrolidone (NMP), were below the limit of detection in the field, but a growth chamber study described here found that NMP can persist in pollen for up to 7 d with average concentrations of 69.3 ppm. Concurrent larval rearing studies found novaluron and NMP to be toxic to developing honey bees at doses as low as 100 ppb and 100 ppm, respectively. Nucleus colony feeding studies found that chronic exposure to Rimon 0.83EC at doses as low as 200 ppm (18.6 ppm novaluron) can result in interruptions to brood production that can last for up to 2 wk after exposure. Taken together, these data indicate the use of Rimon 0.83EC on blooming flowers is a significant threat to honey bee reproduction, and suggest the need for more strict and clear usage guidelines.

Biomonitoring of exposure to N-methyl-2-pyrrolidone in workers of the automobile industry

N-methyl-2-pyrrolidone (NMP) is an important organic solvent for varnishes in industry. NMP has been previously shown to be a developmental toxicant in rodents. This study reports current exposures to NMP in the spraying department of an automobile plant using biological monitoring. Two specific metabolites, 5-hydroxy-N-methyl-2-pyrrolidone (5-HNMP) and 2-hydroxy-N-methyl-succinimide (2-HMSI), were analyzed in 69 urine samples of 14 workers exposed to NMP and 9 nonexposed controls. Three different working tasks ('loading' and 'cleaning' of the sprayer system and 'wiping/packing' of the sprayed materials) and three sampling times (preshift, postshift, and preshift of the following day) were studied in exposed workers. Median exposures of 5-HNMP and 2-HMSI in postshift urine of exposed workers were 0.91 and 0.52mg g(-1) creatinine, respectively, whereas median levels in controls were below the limit of detection. Decreased levels of 5-HNMP were observed in preshift urine samples on the following day (0.39mg g(-1) creatinine) in exposed workers, while the concentration of 2-HMSI did not change (0.49mg g(-1) creatinine). Highest exposures occurred during sprayer cleaning with a maximum level of 8.31mg g(-1) creatinine of 5-HNMP in postshift urine. In contrast to 'wipers/packers', no decrease in 5-HNMP could be observed in preshift urine samples on day 2 of the 'loaders' and 'cleaners'. Overall, exposure in terms of 5-HNMP postshift and 2-HMSI preshift of the following day were well below the current biological limit values of the European Union (70 and 20mg g(-1) creatinine). Our results provide initial data on NMP exposure in the automobile industry and suggest that the analysis of 5-HNMP in preshift samples also provides essential information, particularly in situations involving direct handling of liquid NMP-containing formulations.

Determination of N-methyl-2-pyrrolidone and its metabolites in urine by micellar electrokinetic chromatography

A fast and accurate micellar electrokinetic capillary chromatography (MEKC) method was developed for monitoring N-methyl-2-pyrrolidone (NMP) exposure. Baseline separation of NMP and its main metabolites: 5-hydroxy-N-methyl-2-pyrrolidone (5HNMP), N-methylsuccinimide (MSI), 2-hydroxy-N-methylsuccinimide (2HMSI), and 2-pyrrolidone (2P) was obtained within 6 min in an uncoated fused silica capillary using 5 mM phosphate buffer and 140 mM sodium dodecyl sulfate (pH 7.1) as background electrolyte (BGE). On-line UV-detection was performed at 200 nm and the applied electric field was 400 V cm−1. Possible interference of BGE-induced system peaks on separation was investigated by computer simulation and no such interference was observed. The developed MEKC method combined with solid phase extraction for sample preparation was successfully applied to the analysis of urine of rats exposed to NMP. The urinary excretion was determined in 0–6 h and 6–24 h specimens collected after an intragastic administration of 308 mg NMP / kg rat body weight. The results of NMP disposition kinetics in rat urine are reported for NMP and metabolites.

SPE–GC/FTD determination of N-methyl-2-pyrrolidone and its metabolites in urine

An analytical method using a combination of solid-phase extraction (SPE) and gas chromatography with a flame thermionic detector (GC/FTD) was developed for determination of N-methyl-2-pyrrolidone (NMP), N-methylsuccinimide (MSI), and 2-hydroxy-N-methylsuccinimide (2-HMSI) in human urine. The SPE cartridge of poly(divinylbenzene/hydroxymethacrylate) used was directly loaded with urine sample, followed by elution with methyl isobutyl ketone (MIBK) and subsequent centrifugation, and the supernatant was injected into the capillary GC using a DB1701. This method allowed efficient separation of NMP, MSI, and 2-HMSI, which were nearly free of interference by other GC peaks arising from urine. Recoveries of NMP, MSI, and 2-HMSI from the SPE cartridge were about 98, 101, and 67%, respectively, with limits of detection of 0.04, 0.02, and 0.06 mg/L, respectively, which met the regulatory requirements. The present method was used for assay in biological monitoring of workers exposed to NMP in their occupational environment.

Comparative developmental toxicities of the three major metabolites ofN-methyl-2-pyrrolidone after oral administration in rats

The developmental toxicity of the three main metabolites of N-methyl-2-pyrrolidone (NMP) was studied in Sprague-Dawley rats. Pregnant rats were given 5-hydroxy-N-methyl-2-pyrrolidone (5-HNMP; 0, 250, 500, 750 or 1000 mg kg(-1) day(-1)), N-methylsuccinimide (MSI; 0, 500, 750, 1000 or 1250 mg kg(-1) day(-1)), or 2-hydroxyN-methylsuccinimide (2-HMSI; 0, 250, 500, 1000 or 1500 mg kg(-1) day(-1)), by gavage, on gestational days (GD) 6-20. No evidence of maternal toxicity was observed in dams given 5-HNMP. Administration of 2-HMSI resulted in overt maternal toxicity at 500 mg kg(-1) day(-1) and higher doses, as indicated by a significant reduction in weight gain and food consumption at the beginning of treatment. There was no evidence of embryo/fetal toxicity in any of the groups treated with 5-HNMP or 2-HMSI. MSI produced marked developmental toxicity in the presence of maternal effects. Maternal body weight gain and food consumption were affected at 750 mg kg(-1) day(-1) MSI, and above. A significant increase in post-implantation loss occurred at 1250 mg kg(-1) day(-1) MSI, and the incidence of fetuses with external or with visceral malformations was significantly increased at 1000 and 1250 mg kg(-1) day(-1) MSI. Malformations mainly consisted of anasarca, cardiovascular defects and diaphragmatic hernia. Fetal weight was significantly reduced at 1000 and 1250 mg kg(-1) day(-1). The incidence of skeletal variations (predominantly cervical ribs, and delayed ossification of skull bones and sternebrae) was significantly elevated at 750 mg kg(-1) day(-1) and higher doses. However, MSI was much less potent than the parent compound. These results indicate that the embryotoxic and teratogenic effects of NMP are not attributable to these metabolites.

Levels of N-methyl-2-pyrrolidone (NMP) and its metabolites in plasma and urine from volunteers after experimental exposure to NMP in dry and humid air

The aim of this study was to investigate if the uptake of N-methyl-2-pyrrolidone (NMP), a widely used industrial chemical, increases after exposure to NMP in humid air compared to dry air. NMP has been described to be an airway irritant and a developmentally toxic compound. Six male volunteers were exposed to NMP, three at the time, for 8h in an exposure chamber. They were each exposed on four different occasions to air levels of 0 and 20mg NMP/m(3) in dry and humid air. Blood and urine were sampled before, during and up to 5 days after the end of the 8-h exposure. Plasma and urine were analysed for NMP and its metabolites, using liquid chromatography-tandem mass spectrometry. There was no statistically significant increase in the total cumulated excretion of NMP and its metabolites in urine after exposure in humid air as compared to dry air. Furthermore, there were no differences in the levels of peak concentrations in either plasma or urine. Also, no differences were found in AUC between the exposures. However, there were large individual differences, especially for the exposure in humid air. A not previously identified metabolite in human, 2-pyrrolidone (2-P), was identified. The results do not support a significantly higher absorption of NMP at exposure in humid air as compared to dry air. However, the large individual differences support the use of biological monitoring for assessment of NMP exposure. In addition, 2-P was confirmed to be an NMP metabolite in humans. This may be of importance for the developmental toxicity of NMP since 2-P have been described to be a reproductively toxic substance.

Tissue Distribution and Excretion of N-Methyl-2-Pyrrolidone in Male and Female Rats

OBJECTIVES

N-methyl-2-pyrrolidone (NMP) belongs to solvents widely used in the petrochemical industry a well as in the production of pesticides, veterinary drugs and paint removers. NMP is easily absorbed from the respiratory tract, digestive system and through the skin. It is a compound of slight acute toxicity that also displays moderate irritating activity. The aim of this study was to assess tissue distribution and excretion following a single intraperitoneal NMP administration.

MATERIALS AND METHODS

Tissue distribution and excretion of NMP following administration of a single dose of 250 mg/kg body weight (350 kBq/rat) was investigated using 14C. Blood plasma (6 rats per time point) were sampled up to 72 h after administration and determination of radioactivity. Male and female rats (4 animals per time point) were decapitated at appropriate time intervals and examined tissues were removed for determination of radioactivity. Excretion of 14C in urine and feces were also measured. All radioactivity measurements were carried out using a Rackbetta 1209 (LKB, Sweden) liquid scintillation counter.

RESULTS

The highest 14C activity in tissues and internal organs of female and male rats was observed 4 h after administration of the compound. The highest accumulation was detected in the muscles and fat tissue as well as in the liver and testicles. During 72 h following administration, approximately 80% of the dose was excreted in urine. Elimination of the compound in feces was far less significant: only about 5% of the dose was excreted at once.

CONCLUSIONS

The results of the study indicate that there are no significant differences in 14C-NMP tissue distribution between male and female rats; NMP absorption from the peritoneal cavity to blood is rapid, disappearance from plasma is monophase and kidneys are the main route of excretion of NMP and/or its metabolites from the rat body after administration of a dose equal to 10% of LD50. The ability to accumulate NMP and/or its metabolites in testes and seminal vesicles may be the reason for fertility impairment in male rats observed after repeated exposure to this compound.