Gas chromatographic method for the determination of N-acetyl-S-(N-methylcarbamoyl)cysteine, a metabolite of N,N-dimethylformamide and N-methylformamide, in human urine.

A simple method has been developed for the determination of N-acetyl-S-(N-methylcarbamoyl)cysteine in human urine. Treatment of a urine sample (1 ml) with ethanol (2 ml) and potassium carbonate (1.5 g) produces ethyl N-methylcarbamate, which is extracted into ethanol and measured by packed column gas chromatography with nitrogen-sensitive detection. The limit of quantitation in human urine is 1 microgram/ml and the between-sample coefficient of variation is 5-11%. Simultaneously, N,N-dimethylformamide, N-methylformamide and formamide can also be determined.

Mercapturates in the urine of persons exposed to N,N-dimethylformamide.

N,N-dimethylformamide, a nucleophilic aprotic dipolar solvent, has multipurpose uses, especially in the manufacture of plastics. Its acute toxicity for mammals is low; it is hepatotoxic. Vapors are absorbed by the lungs, in the liquid form it causes cutaneous maceration and is rapidly absorbed through the skin. In the organism it is primarily metabolized to N-monomethylformamide, to a lesser extent to formamide. Urine of individuals exposed to N,N-dimethylformamide was newly found to have higher levels of thioethers, most likely mercapturates, as yet of unknown chemical structure. The correlation between the urinary concentrations of mercapturates (y) and N-monomethylformamide (x) can be expressed by equation y = 4.93 + 0.58 x, with the coefficient of correlation r = 0.90. Part of N,N-dimethylformamide metabolites is likely to react with biopolymers, part of it is excreted as metabolic end products, i.e. carbon dioxide, water and urea. Breakdown to mercapturates may implicate N,N-dimethylformamide as being a potential carcinogen.

In vivo metabolism of dimethylformamide and relationship to toxicity in the male rat.

After in vivo administration of dimethylformamide (DMF) to male rats, about 50% of the dose is excreted in urine as N-hydroxymethyl-N-methylformamide (DMF-OH) and about 4% as N-methylformamide (NMF). NMF is not a product of DMF-OH biotransformation but is directly formed from DMF. Comparison of the acute toxicity of DMF, DMF-OH and NMF shows that NMF is more toxic than DMF-OH, which is itself more toxic than DMF. This study explains the different toxicity profile of DMF and NMF which until recently was believed to represent the main metabolite of DMF.

Dimethylformamide risk. An evaluation in the production of artificial organic leather.

This study aimed to evaluate the exposure to DMF during the different stages in the production of synthetic polyurethanic leathers. Environmental surveys and biological surveillances were carried out in order to classify the working areas and the tasks of the employees as regards DMF-risk. Design improvements to reduce, as far as possible, environmental pollution are discussed.

Study on in vivo and in vitro metabolism of dimethylformamide in male and female rats.

The study of dimethylformamide (DMF) metabolism by rat tissues in vitro indicates that formaldehyde is not a metabolic product as previously reported [1]. Furthermore, no other monocarbon derivative (CO, CH3OH, HCOOH, CH4) was detected when DMF was incubated with a fortified liver preparation. One metabolic product is methylhydroxymethylformamide (DMF-OH) measured as N-methylformamide (NMF) due to the breakdown of the hydroxymethyl group during gas chromatography. It was usually believed that the main metabolite excreted in urine following administration of DMF to male and female rats was NMF. The results of this study indicate that DMF-OH constitutes the main metabolite in vivo. A quantitatively less important urinary metabolite, hydroxymethylformamide (NMF-OH), is determined as formamide (F) by gas chromatography. In male and female rats, partial hepatectomy reduces markedly the in vivo biotransformation of DMF. Following administration of DMF or NMF, the total amount of metabolites (DMF-OH and/or NMF-OH) excreted in urine is identical in both sexes, but female rats excrete more unchanged parent compound than male rats. The rate of NMF-OH excretion in urine following high doses of DMF supports the hypothesis that DMF may inhibit its own biotransformation.

Seasonal effects on concentrations of monomethylformamide in urine samples.

Eleven du Pont operators participated in a special dimethylformamide metabolite (monomethylformamide, MMF) urine monitoring study to investigate a possible seasonal influence on urine metabolite concentrations. Variables considered included urine volume, MMF concentration, MMF mass, urine specific gravity, and ambient temperature. Statistical analysis revealed a 13% reduction in urine volume under hot weather conditions as a cause of increased MMF concentrations. A correction for this change in urine volume should be made subjectively.

A therapeutic monitoring assay for N-methylformamide in human serum and urine.

This report describes a gas chromatographic procedure using a packed column and a flame ionization detector, which is suitable for the therapeutic monitoring of N-methylformamide (N-MF). N-MF is a polar compound that induces cancer cell maturation in vitro and exhibits antitumor activity with human tumors xenografted in nude mice. Toxicology studies with mice have shown this compound to be hepatotoxic. N-MF is currently undergoing Phase I clinical trial as an anticancer drug at this institution. In concert with its clinical trial, a method for the analysis of N-MF in biological fluids has been developed to study its pharmacokinetics. This method involves direct injection of urine or acetone-deproteinized serum onto a Chromosorb 103 column, using N,N-diethylformamide as an internal standard.

Studies of the pharmacology of N-methylformamide in mice.

When 400 mg/kg of 14C-methyl-labeled N-methylformamide (NMF) was injected ip into mice, the curve for plasma concentration of radioactivity versus time was superimposable on the curve obtained by measuring unmetabolized NMF with gas-liquid chromatography during the first 24 hrs. Radioactivity in plasma was measurable for 8 days after NMF administration, but NMF was not measurable by gas chromatography beyond 24 hrs after administration. Radioactivity was eliminated from the plasma after 60 hrs, with an apparent half-life of 71.1 hrs. Of the radioactivity injected with NMF, 73.6% was recovered in the urine in 24 hrs; 26.4% of this was unchanged NMF. Three percent of the administered radioactivity was exhaled as 14CO2 in 7 hrs at a constant rate of 0.007% per min. One urinary metablite was a stable precursor of formaldehyde, which decomposed to formaldehyde only after alkaline hydrolysis and may well be N-(hydroxymethyl)-formamide. The areas under the plasma concentration versus time curve were estimated after ip, iv, and oral administration of NMF. The bioavailability of NMF was 1.01 after oral administration and 1.10 after ip administration.

Dimethylformamide and alcohol intolerance.

Facial flushing and other symptoms were reported by 19 of a group of 102 men who worked with dimethylformamide (DMF). Twenty-six of the 34 episodes occurred after the workers had consumed alcoholic drinks. The metabolite N-methylformamide (MF) was detected in the urine on 45 occasions, the highest recorded concentration being 77 microliter/litre. The highest recorded concentration of DMF in air was 200 ppm. The DMF-ethanol reaction is possibly attributable to the inhibition of acetaldehyde metabolism, probably by MF.

Monomethylformamide levels in human urine after repetitive exposure to dimethylformamide vapor.

Eight healthy male subjects were exposed to DMF vapor at a concentration of 8.79 +/- 0.33 ppm for six hours daily for five consecutive days. All urine voided by the subjects was collected from the beginning of the first exposure to 24 hours past the end of the last exposure and each sample was analyzed for monomethylformamide (MMF). MMF was rapidly eliminated from the body with urine values peaking within a few hours following the end of each exposure period. Very little was found in the 24-hour postexposure sample and none was found in a 48-hour postexposure sample. There was no increased excretion of MMF in the urine following repetitive exposure. The mean for the seven-hour (end of exposure) sample was 4.74 microgram/ml or 736.8 microgram. Lower and upper one-sided 95% tolerance limits for 95% of the population were 1.2 microgram/ml (367 microgram) and 13.9 microgram/ml (1625 microgram). The coefficient of variation (CV) for microgram MMF/ml was approximately 25 times more variable than the CV for total microgram.