Development of a sensitive bioanalytical method for determination of PNU-83757 in rat, monkey and human plasma: from LC-UV to LC-MS/MS.

To support pre-clinical pharmacokinetic/toxicokinetic (PK/TK) evaluation, a sensitive bioanalytical method for determination of N-cyano-N'-(tert-pentyl)-N"-(3-pyridinyl) guanidine (PNU-83757), in rat and monkey plasma was required. Although the UV response of PNU-83757 was quite decent and the extracts using solid phase extraction (SPE) were very selective and concentrated, the best limit of quantitation (LOQ) achieved was 0.4 ng ml(-1) using 0.5 ml plasma for extraction and 2 ng ml(-1) using 0.1 ml plasma for extraction, which was insufficient for PK/TK evaluation at lower doses. When using liquid chromatography with atmospheric pressure chemical ionization tandem mass spectrometric detection (LC-APCI-MS/MS, positive ions) and SPE, a LOQ of 0.045 ng ml(-1) for PNU-83757 was reached. Quantitation was accomplished using the precursor --> product ion combinations of m/z 232 --> 162 for PNU-83757 and m/z 236 --> 166 for the internal standard, [2H(4)]PNU-83757, in the multiple reaction monitoring mode. This method has been successfully utilized for PK/TK evaluation in pre-clinical studies and proved to have sufficient sensitivity to determine plasma concentrations for a dose level as low as 1 microg kg(-1) day(-1) in the rat and monkey. Further improvement of this method by using electrospray mass spectrometric detection (LC-ESI-MS/MS, positive ions) and automated membrane SPE, gave an LOQ of 0.008 ng ml(-1), and allowed analysis of large numbers of samples to support clinical PK studies in microg dose levels.

A non-radioactive iothalamate and p-aminohippuric acid high-performance liquid chromatographic method for simultaneously measuring glomerular filtration rate and renal blood flow in the rat.

A high-performance liquid chromatographic (HPLC) assay method has been developed for the quantitative determination of iothalamate and p-aminohippuric acid (PAH) concentrations in serum and urine samples in the male rat. Glomerular filtration rate (GFR) was measured as clearance of iothalamate, while effective renal blood flow (ERBF) was measured as clearance of PAH. The method is simple, rapid and sensitive and detects iothalamate and PAH in rat serum and urine following administration of bolus doses and continuous infusions of iothalamate and PAH. Samples of serum and urine were deproteinized with two volumes of acetonitrile containing the internal standard, and an aliquot chromatographed on a C18 reversed-phase column. The mobile phase was comprised of 0.1 M sodium phosphate with 1.2 mM tetrabutylammonium phosphate: methanol, 85:15 (v/v), at a flow rate of 1.0 mL/min. The analytical column eluate was monitored with a UV detector at 254 nm with quantitation achieved using peak-height ratios. The precision of the method was 6.6 and 3.6% for iothalamate in serum and urine, and 5.6 and 4.9% for PAH in serum and urine, respectively. The lower limit of quantitation was 0.63 microgram/mL for iothalamate and 1.25 microgram/mL for PAH in serum, and 3.1 microgram/mL for iothalamate and 1.5 microgram/mL for PAH in urine. Recovery of iothalamate from serum and urine was 99.9 and 93.5%, respectively. Recovery of PAH from serum and urine was 99.8 and 92.6%, respectively. The present study demonstrated that non-radioactive iothalamate and PAH can be measured simultaneously using a HPLC assay to measure GFR and ERBF in the male rat.

Quantitative determination of itazigrel in rodent diet by reversed-phase HPLC and evaluation of its stability at 20 degrees C.

A simple, accurate and precise procedure for the quantitation of itazigrel (a potent lipophilic inhibitor of collagen and arachidonic acid-induced aggregation being studied for its effects on peripheral vascular disease) from granulated rodent diet is presented. The drug was extracted from rodent diet using methanol + water (80:20) following dissolution of the diet in water. Samples of the supernatant were injected into the HPLC and the eluent was monitored with a fluorescent detector (lambda ex = 320 and lambda em = 430) to achieve analytical specificity. Interday coefficients of variation of the calibration curve slope were +/- 6% on standards between 0 and 1000 micrograms/g. Potency and homogeneity of the drug spiked diet prepared over a 1 year interval at 70, 200 and 600 micrograms/g was 99.3 +/- 2.5%, 100 +/- 1.8%, and 101 +/- 1.9% of label, respectively. Samples prepared for chromatography were stable for 24 h at 20 degrees C, and drug in diet was stable for 102 days when protected from light and stored at 20 degrees C.

High-performance liquid chromatographic determination of methylprednisolone and methylprednisolone 21-[8-[methyl-(2-sulfoethyl)amino]-8-oxoctanoate] sodium salt in human plasma.

A high-performance liquid chromatographic assay method with ultraviolet detection at 243 nm has been developed for the quantitative determination of methylprednisolone (MP) and methylprednisolone 21-[8- [methyl-(2-sulfoethyl)amino]-8-oxoctanoate] sodium salt (MPSO) in human plasma. The method is simple, rapid and sensitive to detect MP and MPSO in human plasma following administration of therapeutic doses of MPSO. The assay procedure involved stabilization of plasma samples by addition of disodium ethylenediaminetetraacetic acid and ion-pair extractions of MPSO with tetraethylammonium chloride. After extracting both drugs and internal standard into chloroform, the extract was evaporated to dryness under nitrogen. The resulting residue was reconstituted in 200-500 microliter of mobile phase and chromatographed on a C18 IBM reversed-phase column (5 micron). The mobile phase was a mixture of water-actetonitrile-isopropanol (71:19.9:10) containing 50 microliter of 0.1 M hydrochloric acid and 0.497 g tetraethylammonium chloride. Propyl p-hydroxybenzoate was used as an internal standard. The chromatographic responses were linear up to about 200 micrograms/ml for MP and 80 micrograms/ml for MPSO in human plasma. The assay detection limit was approximately 7 ng/ml for MP and 25 ng/ml for MPSO in human plasma. Statistical analysis indicated an average recovery of 102.0 +/- 4.71% for MP and 75.2 +/- 2.88% for MPSO. Human plasma levels are reported for MP and MPSO following single-dose intravenous administration of 100-mg equivalents of MPSO.