The pharmacokinetics of pyridostigmine and 3-hydroxy-N-methylpyridinium in the rat: dose-dependent effects after portal vein administration

Determination of Pyridostigmine Bromide in Presence of its Related Impurities by Four Modified Classical Least Square Based Models: A Comparative Study

Introduction:

Novel manipulations of the well-known classical least squares multivariate calibration model were explained in detail as a comparative analytical study in this research work. In addition to the application of plain classical least squares model, two preprocessing steps were tried, where prior to modeling with classical least squares, first derivatization and orthogonal projection to latent structures were applied to produce two novel manipulations of the classical least square-based model. Moreover, spectral residual augmented classical least squares model is included in the present comparative study.

Methods:

3 factor 4 level design was implemented constructing a training set of 16 mixtures with different concentrations of the studied components. To investigate the predictive ability of the studied models; a test set consisting of 9 mixtures was constructed.

Results:

The key performance indicator of this comparative study was the root mean square error of prediction for the independent test set mixtures, where it was found 1.367 when classical least squares applied with no preprocessing method, 1.352 when first derivative data was implemented, 0.2100 when orthogonal projection to latent structures preprocessing method was applied and 0.2747 when spectral residual augmented classical least squares was performed.

Conclusion:

Coupling of classical least squares model with orthogonal projection to latent structures preprocessing method produced significant improvement of the predictive ability of it.

Orthogonal projection to latent structures and first derivative for manipulation of PLSR and SVR chemometric models' prediction: A case study

Novel manipulations of the well-established multivariate calibration models namely; partial least square regression (PLSR) and support vector regression (SVR) are introduced in the presented comparative study. Two preprocessing methods comprising first derivatization and orthogonal projection to latent structures (OPLS) are implemented prior to modeling with PLSR and SVR. Quantitative determination of pyridostigmine bromide (PR) in existence of its two associated substances; impurity a (IMP A) and impurity b (IMP B); was utilized as a case study for achieving comparison. A series consisting of 16 mixtures with numerous percentages of the studied compounds was applied for implementation of a 3 factor 4 level experimental design. Additionally, a series consisting of 9 mixtures was employed in an independent test to verify the predictive power of the suggested models. Significant improvement of predictive abilities of the two studied chemometric models was attained via implementation of OPLS processing method. The root mean square error of prediction RMSEP for the test set mixtures was employed as a key comparison tool. About PLSR model, RMSEP was found 0.5283 without preprocessing method, 1.1750 when first derivative data was used and 0.2890 when OPLS preprocessing method was applied. With regard to SVR model, RMSEP was found 0.2173 without preprocessing method, 0.3516 when first derivative data was used and 0.1819 when OPLS preprocessing method was applied.

Green Simultaneous Chromatographic Separation of Pyridostigmine Bromide and Its Related Substances in Pure Form, Tablets and Spiked Human Plasma

A green, accurate and specific high-performance thin-layer chromatographic (HPTLC) method was developed and validated for simultaneous quantitative determination of pyridostigmine bromide (PR), impurity B (IMP B);3-hydroxy-N-methylpyridinium bromide and impurity A (IMP A); pyridin-3-yl-dimethylcarbamate. The two pharmacopeial impurities are also its main inactive metabolites. Furthermore, IMP B is known to be its alkaline-induced degradation product. Achievable separation of the studied components required silica gel HPTLC F254 plates as a stationary phase and acetone: acetic acid (80:20, v/v) as a developing system. Scanning of the separated bands was done at 260 nm. According to green solvent selection guidelines, acetone and acetic acid are eco-friendly solvents. Validation of the developed method was insured by its acquiesce to international conference on harmonization (ICH) guidelines. The introduced method was successfully achieved for the quantitative determination of PR, IMP B and IMP A in the range of 0.4-10, 2-11 and 0.4-3.5 μg/band, respectively. Successful application of the developed method was done for determination of PR in human plasma in the range of 0.6-10 μg/band, so the proposed HPTLC can be applied in the pharmacokinetic studies. The studied drug was also analyzed in Mestinon® tablets using the developed method.

Novel manipulations of ratio spectra as powerful tools for resolution and quantitative determination of Pyridostigmine bromide and its' related substances; A comparative study

Resolution and quantitative determination of ternary mixture with severely overlapped spectra without any preliminary separation steps represents a big challenge for any analyst. Smart and novel spectrophotometric methods are continuously innovated for achieving the above mentioned target. Novel applications of ratio difference spectrophotometric technique utilizing ratio spectra and derivative ratio spectra are applied in presented work. The proposed methods included derivative ratio difference (DRD) and ratio subtraction ratio difference (RSRD) methods. Comparative study was achieved between the proposed methods and the recently developed induced ratio difference (IRD) method. The developed methods were assessed through the analysis of ternary mixtures with different ratios of Pyridostigmine bromide (PR) and its related substances; impurity a (IMP A) and impurity b (IMP B). Analysis of PR in a pharmaceutical dosage form without any interference from other inactive ingredients was also a successful application of the proposed methods. As per ICH guidelines, the proposed methods were validated ensuring their accuracy, precision and specificity. Statistical comparison between the developed methods and the reference method was done, where calculated F and t values were less than the theoretical ones in regards to accuracy and precision.

A validated HPLC method for the determination of pyridostigmine bromide, acetaminophen, acetylsalicylic acid and caffeine in rat plasma and urine

A method was developed for the separation and quantification of the anti-nerve agent pyridostigmine bromide (PB; 3-dimethylaminocarbonyloxy-N-methyl pyridinium bromide), the analgesic drugs acetaminophen and acetylsalicylic acid, and the stimulant caffeine (3,7-dihydro-1,3,7-trimethyl-1-H-purine-2,6-dione) in rat plasma and urine. The compounds were extracted using C(18) Sep-Pak(R) cartridges then analyzed by high performance liquid chromatography (HPLC) with reversed phase C18 column, and UV detection at 280 nm. The compounds were separated using gradient of 1-85% acetonitrile in water (pH 3.0) at a flow rate ranging between 1 and 1.5 ml/min in a period of 14 min. The retention times ranged from 8.8 to 11.5 min. The limits of detection were ranged between 100 and 200 ng/ml, while limits of quantitation were 150-200 ng/ml. Average percentage recovery of five spiked plasma samples were 70.9+/-9.5, 73.7+/-9.8, 88.6+/-9.3, 83.9+/-7.8, and from urine 69.1+/-8.5, 74.5+/-8.7, 85.9+/-9.8, 83.2+/-9.3, for pyridostigmine bromide, acetaminophen, acetylsalicylic acid and caffeine, respectively. The relationship between peak areas and concentration was linear over range between 100 and 1000 ng/ml. The resulting chromatograms showed no interfering peaks from endogenous plasma or urine components. This method was applied to analyze these compounds following oral administration in rats.

Determination of depleted uranium, pyridostigmine bromide and its metabolite in plasma and urine following combined administration in rats

A simple and reliable method was developed for the quantification of depleted uranium, the anti nerve agent drug pyridostigmine bromide (PB;3-dimethylaminocarbonyloxy-N-methyl pyridinium bromide) and its metabolite N-methyl-3-hydroxypyridinium bromide in rat plasma and urine. The method involved using solid phase extraction and spectrophotometric determination of uranium, and high performance liquid chromatography (HPLC) with reversed phase C(18) column, and UV detection at 280 nm for PB and its metabolite. Uranium was derivatized using dibenzoylmethane (DBM) then the absorbance was measured at 405 nm. PB and its metabolite were separated using a gradient of 1--40% acetonitrile in 0.1% triflouroacetic acid water solution (pH 3.2) at a flow rate of 0.8 ml/min in a period of 14 min. Limits of detection were 2 ng/ml for uranium and 50 ng/ml for PB and its metabolite. Limits of quantitation were between 10 and 100 ng/ml for uranium and the other two analytes, respectively. Average percentage recovery of five spiked plasma samples were 83.7+/-8.6, 76.8+/-6.7, 79.1+/-7.1, and from urine 82.7+/-8.6, 79.3+/-9.5 and 78.0+/-6.2, for depleted uranium, PB and N-methyl-3-hydroxypyridinium bromide, respectively. The relationship between peak areas and concentration was linear for standards between 100 and 1000 ng/ml for all three analytes. This method was applied to analyze the above chemicals and metabolites following combined administration in rats.

Development of a high-performance liquid chromatographic method for the quantification of chlorpyrifos, pyridostigmine bromide, N,N-diethyl-m-toluamide and their metabolites in rat plasma and urine

A method was developed for the separation and quantification of the insecticide chlorpyrifos (O,O-diethyl-O[3,5,6-trichloro-2-pyridinyl] phosphorothioate), its metabolites chlorpyrifos-oxon (O,O-diethyl-O[3,5,6-trichloro-2-pyridinyl] phosphate) and TCP (3,5,6-trichloro-2-pyridinol), the anti-nerve agent drug pyridostigmine bromide (PB; 3-dimethylaminocarbonyloxy-N-methyl pyridinium bromide), its metabolite N-methyl-3-hydroxypyridinium bromide, the insect repellent DEET (N,N-diethyl-m-toluamide), and its metabolites m-toluamide and m-toluic acid in rat plasma and urine. The method is based on using solid-phase extraction and high-performance liquid chromatography (HPLC) with reversed-phase C18 column, and gradient UV detection ranging between 210 and 280 nm. The compounds were separated using a gradient of 1-85% acetonitrile in water (pH 3.20) at a flow-rate ranging between 1 and 1.7 ml/min over a period of 15 min. The retention times ranged from 5.4 to 13.2 min. The limits of detection ranged between 20 and 150 ng/ml, while the limits of quantitation were between 150 and 200 ng/ml. Average percentage recovery of five spiked plasma samples was 80.2+/-7.9, 74.9+/-8.5, 81.7+/-6.9, 73.1+/-7.8, 74.3+/-8.3, 80.8+/-6.6, 81.6+/-7.3 and 81.4+/-6.5, and from urine 79.4+/-6.9, 77.8+/-8.4, 83.3+/-6.6, 72.8+/-9.0, 76.3+/-7.7, 83.4+/-7.9, 81.6+/-7.9 and 81.8+/-6.8 for chlorpyrifos, chlorpyrifos-oxon, TCP, pyridostigmine bromide, N-methyl-3-hydroxypyridinium bromide, DEET, m-toluamide and m-toluic acid, respectively. The relationship between peak areas and concentration was linear over a range between 200 and 2000 ng/ml.

Chromatographic method for the determination of diazepam, pyridostigmine bromide, and their metabolites in rat plasma and urine

This study describes a chromatographic method for the determination of diazepam, an anxiolytic drug that is also used as an antidote against nerve agent seizures, its metabolites N-desmethyldiazepam, and temazepam, the anti-nerve agent drug pyridostigmine bromide (PB; 3-dimethylaminocarbonyloxy-N-methyl pyridinium bromide) and its metabolite N-methyl-3-hydroxypyridinium bromide in rat plasma and urine. The compounds were extracted using C18 Sep-Pak Vac 3cc (500 mg) cartridges and separated using isocratic mobile phase of methanol, acetonitrile and water (pH 3.2) (10:40:50) at a flow-rate of 0.5 ml/min in a period of 12 min, and UV detection ranging between 240 and 280 nm. The limits of detection for all analytes ranged between 20 and 50 ng/ml, while limits of quantitation were 100 ng/ml. Average percentage extraction recoveries of five spiked plasma samples were 79.1+/-7.7, 83.5+/-6.4, 83.9+/-5.9, 71.3+/-6.0 and 77.7+/-5.6, and from urine 79.4+/-7.9, 83.1+/-6.9, 73.6+/-7.7, 74.3+/-7.1 and 77.6+/-5.9 for diazepam, N-desmethyldiazepam, temazepam, pyridostigmine bromide, and N-methyl-3-hydroxypyridinium bromide, respectively. The relationship between peak areas and concentration was linear over the range between 100 and 1000 ng/ml. This method was applied to determine the above analytes following a single oral administration in rats as a tool to study the pharmacokinetic profile of each compound, alone and in combination.

Simultaneous determination of pyridostigmine bromide, N,N-diethyl-m-toluamide, permethrin, and their metabolites in rat plasma and urine by high-performance liquid chromatography

A rapid and simple method was developed for the separation and quantification of the anti nerve agent drug pyridostignmine bromide (PB; 3-dimethylaminocarbonyloxy-N-methyl pyridinium bromide) its metabolite N-methyl-3-hydroxypyridinium bromide, the insect repellent DEET (N,N-diethyl-m-toluamide), its metabolites m-toluamide and m-toluic acid, the insecticide permethrin (3-(2,2-dichloro-ethenyl)-2,2-dimethylcyclopropanecarboxylic acid(3-phenoxyphenyl)methylester), and two of its metabolites m-phenoxybenzyl alcohol, and m-phenoxybenzoic acid in rat plasma and urine. The method is based on using C18 Sep-Pak cartridges for solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC) with reversed-phase C18 column, and gradient UV detection ranging between 208 and 230 nm. The compounds were separated using gradient of 1 to 99% acetonitrile in water (pH 3.20) at a flow-rate ranging between 0.5 and 1.7 ml/min in a period of 17 min. The retention times ranged from 5.7 to 14.5 min. The limits of detection were ranged between 20 and 100 ng/ml, while limits of quantitation were 150-200 ng/ml. Average percentage recovery of five spiked plasma samples were 51.4+/-10.6, 71.1+/-11.0, 82.3+/-6.7, 60.4+/-11.8, 63.6+/-10.1, 69.3+/-8.5, 68.3+/-12.0, 82.6+/-8.1, and from urine 55.9+/-9.8, 60.3+/-7.4, 77.9+/-9.1, 61.7+/-13.5, 68.6+/-8.9, 62.0+/-9.5, 72.9+/-9.1, and 72.1+/-8.0, for pyridostigmine bromide, DEET, permethrin, N-methyl-3-hydroxypyridinium bromide, m-toluamide, m-toluic acid, m-phenoxybenzyl alcohol and m-phenoxybenzoic acid, respectively. The relationship between peak areas and concentration was linear over the range between 100 and 5000 ng/ml. This method was applied to analyze the above chemicals and metabolites following their administration in rats.