Rapid determination of a new angiotensin-converting enzyme inhibitor, imidapril, and its active metabolite in human plasma by negative-ion desorption chemical ionization-tandem mass spectrometry (MS/MS)

Kinetic study of the alkaline degradation of imidapril hydrochloride using a validated stability indicating HPLC method

An aqueous alkaline degradation study was performed for imidapril hydrochloride (IMD) drug in the presence of its degradation products and an isocratic stability indicating method was presented using HPLC.

Determination of a novel ACE inhibitor in the presence of alkaline and oxidative degradation products using smart spectrophotometric and chemometric methods

Simple, accurate, sensitive and validated UV spectrophotometric and chemometric methods were developed for the determination of imidapril hydrochloride (IMD) in the presence of both its alkaline (AKN) and oxidative (OXI) degradation products and in its pharmaceutical formulation. Method A is the fourth derivative spectra (D4) which allows the determination of IMD in the presence of both AKN and OXD, in pure form and in tablets by measuring the peak amplitude at 243.0 nm. Methods B, C and D, manipulating ratio spectra, were also developed. Method B is the double divisor–ratio difference spectrophotometric one (DD–RD) by computing the difference between the amplitudes of IMD ratio spectra at 232 and 256.3 nm. Method C is the double divisor-first derivative of ratio spectra method (DD–DR1) at 243.2 nm, while method D is the mean centering of ratio spectra (MCR) at 288.0 nm. Methods A, B, C and D could successfully determine IMD in a concentration range of 4.0–32.0 µg/mL. Methods E and F are principal component regression (PCR) and partial least-squares (PLS), respectively, for the simultaneous determination of IMD in the presence of both AKN and OXI, in pure form and in its tablets. The developed methods have the advantage of simultaneous determination of the cited components without any pre-treatment. The accuracy, precision and linearity ranges of the developed methods were determined. The results obtained were statistically compared with those of a reported HPLC method, and there was no significant difference between the proposed methods and the reported method regarding both accuracy and precision.

Validated liquid chromatographic determination of a novel ACE inhibitor in the presence of its hydrolytic and oxidative degradation products as per ICH guidelines

Imidapril hydrochloride (IMD) is a recently developed prodrug-type angiotensin-converting enzyme (ACE) inhibitor. Due to its instability under both hydrolytic and oxidative conditions, development of rapid, simple and sensitive methods for its determination in the presence of its possible degradation products is essential. We proposed two simple liquid chromatographic methods associated with ultraviolet detection. The first method is an HPTLC-densitometric one in which separation of IMD from its degradation products was achieved followed by densitometric scanning at 220 nm using silica gel F254 plates and chloroform:ethanol:acetic acid (3:0.5:0.1, v/v/v) as the developing system. The second method was based on RP-HPLC in which the separation was performed using C18 analytical column and isocratic elution system with acetonitrile: 0.15% triethylamine (pH=2.2) (40:60, v/v). The optimum flow rate was 1.5 mL min(-1) and the detection was at 220 nm. Validation was conducted in compliance with the ICH guidelines and the methods were successfully applied for IMD determination in its commercial tablets. The obtained results were statistically compared to those obtained by applying reported HPLC method where no significant difference was found in accordance with accuracy and precision.

Determination of imidapril and imidaprilat in human plasma by high-performance liquid chromatography-electrospray ionization tandem mass spectrometry

A sensitive and specific assay of imidapril and its active metabolite, imidaprilat, in human plasma has been developed. This method is based on rapid isolation and high-performance liquid chromatography (HPLC)-electrospray ionization (ESI)-tandem mass spectrometry (MS-MS). Imidapril and imidaprilat were isolated from human plasma using OASIS HLB (solid-phase extraction cartridge), after deproteinization. The eluent from the cartridge was evaporated to dryness, and the residue was reconstituted in mobile phase and injected into the HPLC-ESI-MS-MS system. Each compound was separated on a semi-micro ODS column in acetonitrile-0.05% (v/v) formic acid (1:3, v/v). The selected ion monitoring using precursor-->product ion combinations of m/z 406-->234 and 378-->206, was used for determination of imidapril and imidaprilat, respectively. The linearity was confirmed in the concentration range of 0.2 to 50 ng/ml in human plasma, and the precision of this assay, expressed as a relative standard deviation, was less than 13.2% over the entire concentration range with adequate assay accuracy. The HPLC-ESI-MS-MS method correlates well with the radioimmunoassay method, therefore, it is useful for the determination of imidapril and imidaprilat with sufficient sensitivity and specificity in clinical studies.

Determination of a substance P antagonist in human plasma and urine using high-performance liquid chromatography with ultraviolet absorbance and tandem mass spectrometric detection

A high-performance liquid chromatographic (HPLC) assay using ultraviolet (UV) detection was developed and compared with a HPLC method with tandem mass spectrometric (HPLC/MS-MS) detection for the determination of a substance P receptor antagonist 2(S)-((3,5-bis(trifluoromethyl)benzyl)-oxy)-3(S)-phenyl-4-((3-oxo-1,2,4- triazol-5-yl) methyl)morpholine (Fig. 1, Ia, L-742 694) in human plasma and urine. The drug was isolated from the biological matrix through liquid-liquid extraction. In the HPLC/UV method, the samples were initially injected onto a cyano Hypersil column, and the chromatographic region containing the peaks of interest was heart-cut onto an analytical C-18 Hypersil column via a column switching device. The analyte was quantified by monitoring absorbance at 205 nm. The limit of quantification for I extracted from 1 ml of plasma or urine was 2.5 ng ml-1, and the assays were validated in the concentration range 2.5-500 ng ml-1. The HPLC/MS-MS method were validated in the concentration range 0.2-500 ng ml-1. Both assays provided data with precision, measured as coefficient of variation, better than 10% at all points within the standard curve range and with adequate accuracy.

Radioimmunoassay for imidapril, a new angiotensin-converting enzyme inhibitor, and imidaprilat, its active metabolite, in human plasma and urine

A radioimmunoassay (RIA) was investigated for the determination of imidapril and its active metabolite, imidaprilat, in human plasma and urine. Imidapril is a new angiotensin-converting enzyme inhibitor and an oral prodrug of imidaprilat. Imidapril was determined after conversion to imidaprilat with esterase. Antiserum was raised in rabbits against the p-amino derivative of imidaprilat conjugated to bovine serum albumin. Radioligand was prepared by iodination (125I) of the p-hydroxybenzoylamino derivative of imidaprilat. Cross-reactivities of anti-imidaprilat antiserum for imidapril, its metabolites and several cardiovascular drugs were low. The calibration range was 0.1-100 ng ml-1 using a 100 microliters of human plasma of urine. Intra- and inter-day variations of imidaprilat assay in plasma were 2.0-7.9 and 4.1-6.2%, respectively, and intra- and inter-day variations of imidapril assay in plasma were 5.4-10.7 and 7.9-18.1%, respectively. The variations of the assay in urine were a little smaller than those in plasma. The recovery of imidaprilat and imidapril spiked in plasma or urine samples was approximately 100%. A good correlation between RIA and high-performance liquid chromatograpy was observed for both plasma and urine samples. Furthermore, this method was applied to the determination of imidaprilat and imidapril in human plasma and urine samples, for the evaluation of the pharmacokinetics of imidapril in humans. From the results, it was demonstrated that the developed RIA was useful for the determination of imidaprilat and imidapril in human plasma and urine, and was applicable to pharmacokinetic studies in humans.

Determination of a glycine/NMDA receptor antagonist in human plasma and urine using column-switching high-performance liquid chromatography with ultraviolet, fluorescence and tandem mass spectrometric detection

High-performance liquid chromatography (HPLC) assays using ultraviolet (UV) and fluorescence (FL) detection were developed and compared with a liquid chromatography/tandem mass spectrometry (LC/MS-MS) method for determination of the glycine receptor antagonist 7-chloro-4-hydroxy-3-(3-phenoxy)phenyl-2(1H)-quinolone (L-701, 324, I) in human plasma and urine. The drug and internal standard (II) were isolated from the biological matrix through liquid-liquid extraction. In the HPLC-UV and HPLC-FL methods, the samples were initially injected onto a Cyano BDS Hypersil column, and the chromatographic region containing the peaks of interest was heart-cut onto an analytical C-18 BDS Hypersil column via a column-switching device. The analyte was quantified by monitoring either absorbance at 226 nm or fluorescence at 385 nm following 230 nm excitation. The limit of quantitation for I extracted from 1 ml of plasma or urine was 5 ng ml-1, and the assays were validated in the concentrated range of 5-200 ng ml-1. The LC/MS-MS method also utilized a column-switching protocol and was validated in the concentration range of 1-200 ng ml-1. Both assays provided data with precision and accuracy within less than 10% for all points in the standard curve range.