Developmental toxicity of N-methyl-2-pyrrolidone administered orally to rats

Evaluation of new propofol aqueous solutions for intravenous anesthesia

The aim of this study was to evaluate the potential of using three new aqueous formulations of propofol for intravenous (i.v.) anesthesia. The first formulation can be prepared by using hydroxypropyl-gamma-cyclodextrin (HP-gamma-CD) as a solubilizer. Phase-solubility analysis showed a linear increase in the solubility of propofol to a maximum of 16.6 mg/ml in 30% (w/v) HP-gamma-CD. Moreover, phase-solubility studies demonstrated that 18% (w/v) HP-beta-CD or SBE-beta-CD and 24% HP-gamma-CD solutions, respectively, are required to dissolve 10mg of propofol in 1 ml of the vehicle; the corresponding solutions, however, are slightly hypertonic. Autoclaving the 10 mg/ml CD-based formulations for 15 min at 121 degrees C caused a change in pH which was more evident for the HP-beta-CD-based formulation while, in any case, no detectable fall in propofol concentration was observed. The second formulation herein evaluated is a co-solvent mixture (i.e., propylene glycol:water (1:1), v/v) which is able to dissolve 10 mg/ml of the anesthetic agent. However, although it is simple to prepare, the stability of this formulation is limited. The third aqueous formulation can be prepared by using the prolinate ester of propofol and its water-soluble derivative dissolved in water at equimolar concentration. The efficacy of all these formulations as i.v. anesthetic agents was assessed using a pharmacodynamic measure (onset and duration of loss of the righting reflex, LORR), and compared with that of the commercial propofol formulation (Diprivan, 10 mg/ml) in rats. It was found that minimizing the amount of cyclodextrin in all CD-based formulations, anesthetic effects comparable to those of propofol in Diprivan were still observed. Moreover, the prolinate ester constituted an effective i.v. anesthetic formulation with the same duration of action but with a longer induction time than Diprivan.

Human experimental exposure to N-methyl-2-pyrrolidone (NMP): toxicokinetics of NMP, 5-hydroxy- N-methyl-2-pyrrolidone, N-methylsuccinimide and 2-hydroxy- N-methylsuccinimide (2-HMSI), and biological monitoring using 2-HMSI as a biomarker

OBJECTIVE

N-methyl-2-pyrrolidone (NMP) is a strong and selective organic solvent with an extensive and increasing use. It has been reported to be a compound that is toxic to the reproductive system. The aim of this study was to evaluate toxicokinetics parameters for NMP and its metabolites, 5-hydroxy- N-methyl-2- pyrrolidone (5-HNMP), N-methylsuccinimide (MSI) and 2-hydroxy- N-methylsuccinimide (2-HMSI), and to develop a method for biological monitoring of NMP exposure that uses 2-HMSI as a biomarker.

METHODS

Six healthy, male volunteers were exposed to NMP in an exposure chamber for 8 h at concentrations of 10, 25 and 50 mg/m(3). In addition, three of the subjects were exposed a second time at 50 mg/m(3). Air levels were monitored by Amberlite XAD-7 sampling and gas chromatography (GC) analysis. Levels of NMP and the metabolites in plasma and urine were analysed by GC or GC with mass spectrometry detection.

RESULTS

The concentration of 2-HMSI in plasma and urine rose during exposure and reached a peak approximately 15 h after the end of exposure. It then decayed according to a one-compartment model with a half-time of about 18 h. There were very close correlations between the NMP air levels, on the one hand, and concentrations of 2-HMSI in plasma (r=0.98) and creatinine-adjusted urinary 2-HMSI levels (r=0.96), on the other. The renal clearances were 0.13, 1.4, 0.12 and 1.2 l/h for NMP, 5-HNMP, MSI and 2-HMSI, respectively. The total clearances were 11.4, 3.2, 8.5 and 1.1 l/h for NMP, 5-HNMP, MSI and 2-HMSI, respectively. The apparent volumes of distribution were 41, 28, 120 and 28 l for NMP, 5-HNMP, MSI and 2-HMSI, respectively.

CONCLUSIONS

Toxicokinetics parameters for NMP, 5-HNMP, MSI and 2-HMSI have been estimated. Furthermore, 2-HMSI is applicable as a biomarker of exposure to NMP, and the levels in plasma and urine may be used to indicate an exposure over three days.

Developmental toxicity of N-methyl-2-pyrrolidone in rats following inhalation exposure

The developmental toxicity of inhaled N-methyl-2-pyrrolidone (NMP) was studied in Sprague-Dawley rats. Pregnant rats were exposed whole body to NMP vapours at concentrations of 0, 30, 60 and 120 ppm, 6 h/day, on gestational days (GD) 6 through 20. Maternal body weight gain was significantly decreased at 60 and 120 ppm on GD 6-13 and maternal food consumption was reduced at 120 ppm on GD 13-21. No significant difference in the gestational weight change corrected for the weight of the gravid uterus was observed, whatever NMP concentration. There were no adverse effects on embryo/fetal viability or evidence of teratogenicity at any concentration tested. Fetal toxicity indicated by reduced fetal weight was observed at 120 ppm. Thus, the no-observed-adverse-effect level (NOAEL) for maternal and developmental toxicity was 30 and 60 ppm, respectively.