Determination of 2-hydroxyiminomethyl-1-methyl-pyridinium methanesulphonate (pralidoxime mesylate, P2S) and its degradation products in solution by liquid chromatography

Chromatographic separation and NMR characterization of the isomers of MMB-4, a bis-(pyridiniumaldoxime)

1,1'-Methylenebis{4-[(hydroxyimino)methyl]pyridinium) dichloride (MMB-4), a promising antidote for organophosphate poisoning, has been shown by chromatography and NMR to be a mixture of geometric isomers, predominantly the E/E form. The chromatographically separated isomers have been isolated, directly characterized by NMR to be E/E and E/Z isomers of high purity, and shown by HPLC and NMR to re-equilibrate in solution to the isomeric mixture found in bulk MMB-4. These findings clearly show that a minor component in MMB-4 is not an impurity, but a geometric isomer of the principal component and demonstrate the need to understand equilibrium processes for drug characterizations and isomer distributions of chemicals proposed for animal and human clinical trials. Evidence for the presence of the Z/Z isomer could not be found.

In vitro and in vivo metabolisms of K-48

Metabolic pathways of the oxime K-48 have been elucidated by means of in vitro and in vivo experiments. K-48 exposure to rat liver microsomal fraction resulted in the formation of a hydroxylated derivative, in addition to a small molecular fragment. The in vivo metabolism in rats was investigated after intramuscular administration of 50 mumol oxime. K-48 was present in the rat serum in unchanged form. Similarly, the analysis of rat cerebrospinal fluid indicated the sole occurrence of unchanged K-48. In contrast, unchanged K-48 was not found in the rat urine, where only the metabolite generated by epoxidation on the alkyl chain connecting the two pyridinium rings was present. The presence of unchanged K-48 in the serum and cerebrospinal fluid facilitates quantitative determination using HPLC separation and ultraviolet absorbance detection.

HPLC analysis of K-48 concentration in plasma

K-48 is a new oxime-type compound to be used as an enzyme reactivator in the treatment of exposure to organophosphorous compounds. Plasma concentration of K-48 can be determined using reversed-phase HPLC. Analysis using octyl silica stationary phase and ultraviolet-absorbance detection is fast and simple. K-48 displays a relatively high dose-normalized area under the curve as compared to pralidoxime, which might be beneficial for an antidote. After i.m. administration of 50 mumol K-48, the time course of the concentration can be approximated by a straight line between 15 and 120 min meaning the elimination follows zero-order kinetics.

Simple high-performance liquid chromatographic method for assessing the deterioration of atropine-oxime mixtures employed as antidotes in the treatment of nerve agent poisoning

A set of reversed-phase HPLC conditions for determining the degradation of atropine and the oxime (pralidoxime, obidoxime, or HI-6) in autoinjectors designed for use against nerve agent poisoning is described. The assay conditions for atropine do not require its prior separation from the large molar excess of oxime since both the atropine and tropic acid peaks elute well clear of the oxime and its degradation products and the phenolic preservatives. Further dilution of the sample and simple changes to the mobile phase then provide conditions for the oxime and its major degradation products to be quantitated.

Pralidoxime chloride stability-indicating assay and analysis of solution samples stored at room temperature for ten years

A high-performance liquid chromatographic (HPLC) method is described for quantitation of pralidoxime chloride and its decomposition products 2-carboxy-, 2-formyl-, and 2-(aminocarbonyl)-1-methylpyridinium chloride. These decomposition products and 2-cyano- and 2-(hydroxymethyl)-1-methylpyridinium chloride and 1-methyl-2(1H)-pyridinone were separated from pralidoxime chloride on a silica gel column using a mobile phase of acetonitrile:water (86:14) in which the aqueous component was 8.36 mM in tetraethylammonium chloride and 52.5 mM in acetic acid. This method allows quantitation of the relatively low levels of 2-formyl-1-methylpyridinium chloride formed in acidic solution at room temperature. Sensitivity was shown to be at least 5 ng of the pralidoxime chloride and 15 ng of the 2-carboxy-, 2-formyl-, and 2-(aminocarbonyl)-1-methylpyridinium chloride injected on column. The coefficient of variation was 4% or less for all components measured. Autoinjectors containing 300 mg/mL of pralidoxime chloride in water were stored at room temperature for 8-10 years, followed by analysis for hydrogen cyanide using an ion-selective electrode. Less than 15 micrograms of cyanide per autoinjector was detected. The HPLC analysis of the solutions after being stored an additional 3-4 years at approximately 5 degrees C demonstrated that greater than 90% of the total of all measured components consisted of pralidoxime chloride. The remaining percentage was made up of 2-carboxy-, 2-formyl-, and 2-(aminocarbonyl)-1-methylpyridinium chloride.

Analysis of formulations containing pralidoxime mesylate by liquid chromatography

An improved liquid chromatography procedure has been devised for the analysis of pralidoxime mesylate (P2S) and its degradation products in solution. An additional degradation product, 2-hydroxyaminoiminomethyl-1-methylpyridinium, has been positively identified and its route of formation and that of another recently identified product, 2-hydroxymethyl-1-methylpyridinium, has been established. Previous problems with the chromatography of 2-formyl-1-methylpyridinium have been resolved and the new method will resolve P2S and eight of its degradation products.