Separation of some natural and synthetic corticosteroids in biological fluids and tissues by high-performance liquid chromatography

Determination of corticosteroids in plasma by high-performance liquid chromatography after pre-column derivatization with 2-(4-carboxyphenyl)-5,6-dimethylbenzimidazole

2-(4-Carboxyphenyl)-5,6-dimethylbenzimidazole (CDB) was used as a pre-column derivatization reagent for corticosteroids analysed by high-performance liquid chromatography with fluorimetric detection. Eight corticosteroids were derivatized with CDB to their esters in acetonitrile containing 4-piperidinopyridine and 1-isopropyl-3-(3-dimethylaminopropryl)carbodiimide perchlorate. The resulting CDB esters were extracted with a Sep-Pak C18 cartridge and the esters were separated on a reversed-phase column (Zorbax ODS) with water-methanol (25:75, v/v) containing 5 mmol/l tetramethylammonium hydrogensulphate as the mobile phase. The limits of detection for steroids were 0.06-0.3 pg per 100 microliters of plasma (signal-to-noise = 3). The within-day relative standard deviations (n = 6) were 7.8-11.1%, and day-to-day relative standard deviations (n = 6) were 7.0-10.4%.

Liquid chromatographic analysis of prednisolone, prednisone and their 20-reduced metabolites in perfusion media

A reversed-phase liquid chromatographic assay was developed to quantitate prednisolone, prednisone and the 20 alpha-dihydro and 20 beta-dihydro reduced metabolites of both parent compounds in tissue culture media from in vitro perfusions of the human placental lobule. Steroids were extracted from perfusate, using reversed-phase cartridges, with average recoveries of 95.2% or greater. The internal standard for the analyses was 6 alpha-methylprednisolone. In this assay cortisol coelutes with prednisolone, however, no other significant interferences were found. Assay of each steroid was linear in the range 0-1 microgram/ml. Intra-assay coefficients of variation were measured at 10 and 750 ng/ml with ranges of 3.4% (20 alpha-dihydroprednisone) to 8.8% (20 beta-dihydroprednisolone) and 4.1% (20 beta-dihydroprednisone) to 8.8% (prednisone). The corresponding inter-assay coefficients of variation were 3.3% (20 alpha-dihydroprednisone) to 9.1% (20 beta-dihydroprednisolone) and 1.9% (prednisolone) to 3.5% (prednisone). The analyses utilized two C18 columns which were linked together and maintained at 40 degrees C.

Determination of dexamethasone in human plasma and urine by electron-impact mass spectrometry

A gas chromatographic-electron-impact mass spectrometric method for the determination of dexamethasone in biological fluids has been developed. Quantitation by isotopedilution mass spectrometry was carried out by selected-ion monitoring on the molecular ions of the tetra(trimethylsilyl) derivative of dexamethasone and of dexamethasone M+9 (m/z 680 and 689, respectively). The sensitivity, specificity, precision and accuracy of the method were demonstrated to be satisfactory for application to pharmacokinetic and bioavailability studies of dexamethasone after administration of a therapeutic dose.

Comparative distribution and metabolism of triamcinolone acetonide and cortisol in the rat embryomaternal unit

Triamcinolone acetonide (TAC) is teratogenic in rats while cortisol has been reported as not teratogenic. The objective of this investigation was to determine whether this difference in teratogenicity could be due to a difference in the metabolism and distribution of the parent compound in the embryomaternal unit. 3H-TAC and 14C-cortisol were administered intramuscularly to pregnant rats on day 12 of gestation. These dams were killed at each of the following time points after injection: 0.5, 1, 3, 6 and 24 hr. Maternal plasma and embryos were analyzed by high performance liquid chromatography (HPLC) and liquid scintillation counting. The plasma concentration of parent TAC was significantly greater than that for parent cortisol at all time points. The plasma elimination half-life for TAC, 86 min, was also calculated to be significantly longer than that for cortisol, 8 min. Furthermore, the percentage of total plasma radioactivity representing HPLC resolved TAC was much higher than that representing cortisol at all time points. The concentration of TAC in the embryos was significantly greater than for cortisol at all time points. The elimination half-life for unchanged TAC in the embryos was 142 min compared to 22 min for cortisol. The percentage of total radioactivity in the embryos representing unchanged TAC was similar to that found in maternal plasma while the percentage of total radioactivity representing unchanged cortisol was much lower than that found in maternal plasma. These findings support the hypothesis that differences in the distribution and metabolism of the parent compound are a critical factor in determining the teratogenicity of that compound.

Distribution and metabolism of triamcinolone acetonide in the rat embryomaternal unit during a teratogenically sensitive period

The distribution and metabolism of triamcinolone acetonide (TAC) in the rat embryomaternal unit were investigated during a teratogenically sensitive period. Pregnant rats (Day 12 of gestation) were injected im with 0.125 or 0.5 mg/kg [3H]TAC. Maternal plasma and embryos were collected at selected time points and analyzed by HPLC and liquid scintillation counting. No significant differences in the percentage of total radioactivity representing unchanged TAC, concentration of TAC, or its elimination half-life were detected in either plasma or embryos of the two dose groups. These results provide evidence that the metabolism and distribution of TAC in the rat embryomaternal unit are dose independent over this known teratogenic dose range. To determine whether multiple administration of TAC resulted in any alterations in maternal or embryonal exposure, the same parameters were evaluated following one (Day 12), two (Days 12 and 13), or three (Days 12, 13, and 14) injections of [3H]TAC (0.5 mg/kg, im). The only alterations detected were an increase in the percentage of total radioactivity in maternal plasma representing unchanged TAC at 1 hr following the second or third injection and an increase in the embryonal concentration of TAC at the same time points.