Urinary profile of methylprednisolone and its metabolites after oral and topical administrations

Methylprednisolone (MP) is prohibited in sports competitions when administered by systemic routes; however its use by topical administration is allowed. Therefore, analytical approaches to distinguish between these different administration pathways are required. A reporting level of 30ng/mL was established for this purpose. However, the suitability of that reporting level for MP is not known. In the present work, excretion profiles of MP and different metabolites after oral and topical administrations have been compared. A method for the quantification of MP and the qualitative detection of fifteen previously reported metabolites has been validated. The method involved an enzymatic hydrolysis, liquid-liquid extraction and analysis by liquid chromatography coupled to tandem mass spectrometry. The method was found to be linear, selective, precise and accurate. The high sensitivity (limit of detection 0.1ng/mL) and linear range (0.1-250ng/mL) achieved allowed for the quantification of MP at both the low concentrations present after topical administration and the high concentrations detected after oral intake. The method was applied to samples collected after oral (4 or 40mg) and topical administration (10mg of MP aceponate/day for 5 consecutive days) to healthy volunteers. After oral administration, MP and all metabolites were detected in urines collected up to at least 36h. Only MP and five metabolites were detected in samples obtained after topical treatment. As expected, concentrations of MP after topical administration were well below current reporting level (30ng/mL), however 3 out of 4 samples in range 8-24h after the low oral dose (4mg) were also below that concentration. Taking into account metabolites detected after both administration routes, metabolites 16β,17α,21-trihydroxy-6α-methylpregna-1,4-diene-3,11,20-trione (M8) and 17α,20α,21-trihydroxy-6α-methylpregna-1,4-diene-3,11-dione (M11) are best markers to differentiate between topical and oral administrations. Their signals after topical administration were lower than those obtained in the first 48h after all oral doses.

Using complementary mass spectrometric approaches for the determination of methylprednisolone metabolites in human urine

RATIONALE

The metabolism of methylprednisolone is revisited in order to find new metabolites that could be important for distinguishing between different routes of administration. Recently developed liquid chromatography/tandem mass spectrometry (LC/MS/MS) strategies for the detection of corticosteroid metabolites have been applied to the study of methylprednisolone metabolism.

METHODS

The structures of these metabolites were studied using two complementary mass spectrometric techniques: LC/MS/MS in product ion scan mode with electrospray ionization and gas chromatography/mass spectrometry (GC/MS) in full scan mode with electron ionization. Metabolites were also isolated by semipreparative liquid chromatography fractionation. Each fraction was divided into two aliquots; one was studied by LC/MS/MS and the other by GC/MS after methoxyamine-trimethylsilyl derivatization.

RESULTS

The combination of all the structural information allowed us to propose a comprehensive picture of methylprednisolone metabolism in humans. Overall, 15 metabolites including five previously unreported compounds have been detected. Specifically, 16β,17α,21-trihydroxy-6α-methylpregna-1,4-diene-3,11,20-trione, 17α,20β,21-trihydroxy-6α-methylpregna-1,4-diene-3, 11-dione, 11β,17α,21-trihydroxy-6α-hydroxymethylpregna-1,4-diene-3,20-dione, 11β,17α,20ξ,21-tetrahydroxy-6α-hydroxymethylpregna-1,4-diene-3-one, and 17α,21-dihydroxy-6α-hydroxymethylpregna-1,4-diene-3,11,20-trione are proposed as feasible structures for the novel metabolites. In addition to the expected biotransformations: reduction of the C20 carbonyl, oxidation of the C11 hydroxy group, and further 6β-hydroxylation, we propose that hydroxylation of the 6α-methyl group can also take place.

CONCLUSIONS

New metabolites have been identified in urine samples collected after oral administration of 40 mg of methylprednisolone. All identified metabolites were found in all samples collected up to 36 h after oral administration. However, after topical administration of 5 g of methylprednisolone aceponate, neither the parent compound nor any of the metabolites were detected.

A sensitive and specific precursor ion scanning approach in liquid chromatography/electrospray ionization tandem mass spectrometry to detect methylprednisolone acetate and its metabolites in rat urine

A new, simple, sensitive and specific liquid chromatography/electrospray ionization tandem mass spectrometric (LC/ESI-MS/MS) method in precursor ion scanning (PIS) mode has been developed for the rapid detection of methylprednisolone acetate (MPA) and its metabolites in rat urine. A suitable product ion specific for methylprednisolone (MP) and MPA was selected after a fragmentation study on 20 (cortico)steroids at different collision energies (5-40 eV). Urine samples were simply treated with acetonitrile then dried in a SpeedVac system. The method was validated and compared with other PIS methods for detecting corticosteroids in human urine. It was more sensitive, with limit of detection (LOD) and lower limit of quantitation (LLOQ), respectively, of 5 and 10 ng mL(-1). The method was applied for the analysis of rat urine collected before and after (24, 48, 72 h) intra-articular (IA) injection of a marketed formulation of MPA (Depo-Medrol(R)). MS/MS acquisitions were taken at different collision energies for the precursor ions of interest, detected in PIS mode, to verify the MP-related structure. Six different metabolites were detected in rat urine, and their chemical structures were assigned with a computational study.

Evaluation of different scan methods for the urinary detection of corticosteroid metabolites by liquid chromatography tandem mass spectrometry

Different approaches for the non-target detection of corticosteroids in urine have been evaluated. As a result of previous studies about the ionization (positive/negative) and fragmentation of corticosteroids, several methods based on both precursor ion (PI) and neutral loss (NL) scans are proposed. The applicability of these methods was checked by the injection of a standard solution containing 19 model compounds. Five of the studied methods (NL of 76 Da; PI of 77, 91 and 105; PI of 237; PI of 121, 147 and 171; and NL of 38 Da) exhibited satisfactory results at the concentration level checked (corresponding to 20 ng/ml in sample). Some other methods in negative ionization mode such as the NL of 104 Da were found to lack sufficient sensitivity. Some of the applied methods were found to be specific for a concrete structure (NL of 38 Da for fluorine containing corticosteroids) while others showed a wide range applicability (PI of 77, 91 and 105 showed response in all model compounds). Interference by endogenous compounds was also tested by the analysis of negative urines and urines spiked with different corticosteroids. The suitability of these methods for the detection of corticosteroid metabolites was checked by the analysis of urine samples collected after the administration of methylprednisolone and triamcinolone. A combination of the reported methods seems to be the approach of choice in order to have a global overview about the excreted corticosteroid metabolites.

Determination of methylprednisolone acetate in biological fluids at gold nanoparticles modified ITO electrode

The electrochemical behavior of a corticosteroid methylprednisolone (MP), used for doping, has been studied at gold nanoparticles modified indium tin oxide (nanoAu/ITO) electrode. The nanoAu/ITO electrode exhibited an effective catalytic response towards its oxidation and lowered its oxidation potential by approximately 127 mV when compared with bare ITO electrode. Oxidation of MP has been carried out in phosphate containing electrolyte in the pH range 2.13-10.00 and a well-defined oxidation peak was noticed. Linear concentration curves are obtained over the concentration range 0.01-1.0 microM with a detection limit of 2.68 x 10(-7)M at nanoAu/ITO electrode. A diffusion coefficient of 2.36 x 10(-6)cm(2)/s is calculated for MP using chronoamperometry. The proposed method is effectively applied to detect the concentration of MP in pharmaceutical formulations and human blood plasma and urine samples. A comparison of MP concentration determined in blood plasma and urine by the proposed method and GC/MS indicated that the results are essentially similar. It is believed that the method will be useful in determining this drug in case of doping.

Determination of Free and Total Cortisol in Plasma and Urine by Liquid Chromatography-Tandem Mass Spectrometry

Cortisol is an important adrenal steroid hormone involved in the regulation of metabolic homeostasis. A new liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) multiple reactant monitoring (MRM) procedure for the measurement of cortisol concentration in plasma ultrafiltrate, whole plasma, and urine was developed and validated. Plasma, plasma ultrafiltrate, or urine was extracted by ethyl acetate. The extract was subjected to liquid chromatography with an Inertsil ODS-3 column with an aqueous NH4Cl (1 mM, pH 9.0):methanol mobile phase. The presence of NH4Cl in the mobile phase induced the formation of [M+Cl] in the first quadrupole at m/z 397 and 409 for cortisol and 6alpha-methylprednisolone (internal standard), respectively. In the collision cell, the complex dissociated to the neutral parent and the chloride ion at m/z 35; the latter ion was used for quantification. The calibration curve was linear from 0.5 to 100 ng/mL. The lower limit of quantification was 0.50 ng/mL and the limit of detection was 0.25 ng/mL. For quality control samples prepared in water, the intrabatch assay precision was 5.6%, 9.6%, and 9.9% at 50, 10, and 1 ng/mL, respectively. The interbatch assay precision was 4.2%, 6.3%, and 7.5% at 50, 10, and 1 ng/mL, respectively. For measurement of endogenous cortisol in plasma and urine samples, the intra-assay and interassay precision was 10.8% and 4.8% for total plasma cortisol, 13.1% and 5.2% for free plasma cortisol, 10.9% and 13.1% for cortisol protein-binding free fraction, and 8.9% and 14.4% for urine cortisol, respectively. A simple procedure of ultrafiltration coupled with the highly sensitive LC-MS/MS quantification offered a rapid and reproducible assay for plasma free cortisol, which may be useful in the assessment of adrenal function in patients, especially critically ill patients with abnormal protein binding. It may also be useful for plasma and urinary cortisol measurements in pharmacodynamic studies of adrenocorticoid response.

Analysis of corticosteroids in equine urine by liquid chromatography-mass spectrometry

A liquid chromatography-mass spectrometry (LC-MS) method for the analysis of corticosteroids in equine urine was developed. Corticosteroid conjugates were hydrolysed with beta-glucuronidase; free and enzyme-released corticosteroids were then extracted from the samples with ethyl acetate followed by a base wash. The isolated corticosteroids were detected by LC-MS and confirmed by LC-MS-MS in the positive atmospheric pressure chemical ionisation mode. Twenty-three corticosteroids (comprising hydrocortisone, deoxycorticosterone and 21 synthetic corticosteroids), each at 5 ng/ml in urine, could easily be analysed in 10 min.

High-performance liquid-chromatographic-atmospheric-pressure chemical-ionization ion-trap mass-spectrometric identification of isomeric C6-hydroxy and C20-hydroxy metabolites of methylprednisolone in the urine of patients receiving high-dose pulse therapy

Fourteen metabolites of methylprednisolone have been analysed by gradient-elution high-performance liquid chromatography coupled with tandem mass spectrometry (LC-MS-MS). The compounds were separated on a Cp Spherisorb 5 microm ODS column connected to a guard column packed with pellicular reversed phase. The mobile phase was an acetonitrile- 1.0% aqueous acetic acid gradient at a flow rate of 1.5 mL min(-1) The analysis gave a complete picture of parent drug, prodrugs and metabolites, and the alpha/beta stereochemistry was resolved. The short (1-2 h) elimination half-life of methylprednisolone is explained by extensive metabolism. The overall picture of the metabolic pathways of methylprednisolone is apparently simple-reduction of the C20 carbonyl group and further oxidation of the C20,C21 side chain (into C21COOH and C20COOH), in competition with or in addition to oxidation at the C6 position.

Isolation and identification of the C6-hydroxy and C20-hydroxy metabolites and glucuronide conjugate of methylprednisolone by preparative high-performance liquid chromatography from urine of patients receiving high-dose pulse therapy

In the present study metabolites of methylprednisolone were detected using gradient elution high-performance liquid chromatography. Separation was performed by a Cp Spherisorb ODS 5 microm (250 mmx4.6 mm I.D.) column, connected to a guard column, packed with pellicular reversed phase. The mobile phase was a mixture of acetonitrile and 1% acetic acid in water. At t = 0, this phase consisted of 2% acetonitrile and 98% acetic acid 1% in water (v/v). During the following 35 min the phase changed linearly until it attained a composition of acetonitrile-buffer (50:50, v/v). At 40 min (t = 40) the mobile phase was changed over 5 min to the initial composition, followed by equilibration during 2 min. The flow-rate was 1.5 ml/min. UV detection was achieved at 248 nm. We have isolated the respective compounds with the most abundant concentration and suggested their chemical structure based on NMR, IR, UV, MS, retention behaviour and melting points. The c/, stereochemistry could not be solved in this study. The overall picture of the metabolic pathways of methylprednisolone is apparently simple: reduction of the C20 carbonyl group and further oxidation of the C20-C21 side chain (into C21-COOH and C20-COOH), in competition with or additional to the oxidation at the C6-position.

Determination of urinary free cortisol by HPLC

We here report a reversed-phase HPLC method for the determination of free cortisol in human urine, using methylprednisolone as the internal standard. Before chromatography, samples were extracted with a C18 solid-phase extraction column and the steroids were separated on a LiChrospher 100 C18 column with a mobile phase of methanol/acetonitrile/water (43/3/54 by vol). Linearity, precision, and accuracy of the method were established. The detection limit was 10 pmol of cortisol, and total CVs were < 8%. With various solid-phase extraction columns the recovery of cortisol was 36-97%; recovery of the internal standard was 43-85%. Study of interference by 6 other steroids and metabolites and 24 drugs showed that carbamazepine and digoxin partly overlapped with cortisol, but this interference could be reduced by modification of the mobile phase. The HPLC method was compared with an RIA and an automated immunoassay method. The results obtained by HPLC averaged 40% of the RIA values.

Pharmacokinetic and pharmacodynamic assessment of bioavailability for two prodrugs of methylprednisolone

AIMS

The aim of this study was to establish whether pharmacokinetic differences between two pro-drugs of methylprednisolone (MP) are likely to be of clinical significance.

METHODS

This study was a single-blind, randomized, crossover design comparing the bioequivalence of MP released from the pro-drugs Promedrol (MP suleptanate) and Solu-Medrol (MP succinate) after a single 250 mg (MP equivalent) intramuscular injection to 20 healthy male volunteers. Bioequivalence was assessed by conventional pharmacokinetic analysis, by measuring pharmacodynamic responses plus a novel approach using pharmacokinetic/pharmacodynamic modeling. The main measure of pharmacodynamic response was whole blood histamine (WBH), a measure of basophil numbers.

RESULTS

The MP Cmax was less for MP suleptanate due to a longer absorption halflife of the prodrug from the intramuscular injection site. The bioavailability of MP was equivalent when based on AUC with a MP suleptanate median 108% of the MP succinate value (90% CI: 102-114%). For Cmax the MP suleptanate median was 81% of the MP succinate value (90% CI: 75-88%). The tmax for MP from MP suleptanate was delayed relative to MP succinate. The median difference was 200% (90% non-parametric CI: 141-283%). The area under the WBH effect-time curve (AUEC) and the maximum response (Emax) were found to be equivalent (90% CI: 98-113% and 93-109% respectively). The maximum changes in other white blood cell counts, blood glucose concentration and the parameters of the pharmacodynamic sigmoid Emax model (EC50, Emax and gamma) were also not significantly different between prodrugs.

CONCLUSIONS

MP suleptanate is an acceptable pharmaceutical alternative to MP succinate. The use of both pharmacokinetic and pharmacodynamic response data together gives greater confidence in the conclusions compared with those based only on conventional pharmacokinetic bioequivalence analysis.

Simultaneous determination of cortisol and cortisone in urine by reversed-phase high-performance liquid chromatography. Clinical and doping control applications

A reversed-phase high-performance liquid chromatography (HPLC) method for the simultaneous determination of cortisol and cortisone in human urine samples using methylprednisolone as the internal standard is described. The method involves the systematic use of isocratic mobile phases of water and methanol, acetonitrile or tetrahydrofuran and a reversed-phase Hypersil C18 column. A water-acetonitrile mixture used as the mobile phase proved to be the most adequate one for analyzing urine samples purified by solvent extraction. The proposed method is sensitive, reproducible and selective. It was applied to the determination of cortisol and cortisone in several human urine samples: healthy subjects, sportsmen before and/or after stress for doping control purposes, and patients with Cushing's syndrome.

Pharmacokinetics of methylprednisolone hemisuccinate and methylprednisolone in chronic liver disease

The disposition of methylprednisolone (MP) and its prodrug hemisuccinate (MPHS) was assessed in six middle-aged patients with chronic liver disease (CLD) and compared with six younger, healthy subjects after a single IV dose of 25.4 mg of MPHS. Blood and urine samples were collected over 12 hours. Plasma and urine concentrations of MPHS and MP and plasma cortisol were measured by HPLC. MPHS clearance (CL) was significantly reduced in the CLD group (495 vs. 1389 mL/hr/kg) whereas volume of distribution (Vss) of MPHS (about 0.35 1/kg) did not differ. The elimination half-life, t1/2 beta, was significantly longer in CLD (0.61 vs. 0.32 hr). The percent recovery of unchanged MPHS in urine was similar (about 9%) in both groups. The kinetic parameters of MP did not differ between the two groups for: clearance (about 370 L/hr/kg IBW), Vss (about 1.3 L/kg), and t1/2 beta (about 3.0 hr). The suppression t1/2 of cortisol after MPHS was longer (3.9 vs. 1.9 hr) indicating metabolic pathways for cortisol and MP are affected differently in CLD. Reduction in MPHS CL may reflect altered hepatic blood flow due to both cirrhosis and age effects. However, good availability of MP from MPHS and lack of perturbation of MP pharmacokinetics in CLD patients may provide therapeutic advantages in selection of this glucocorticoid. This is the first study that characterizes the disposition of the prodrug MPHS and the formation of MP simultaneously in CLD patients.

Methylprednisolone hemisuccinate and metabolites in urine from patients receiving high-dose corticosteroid therapy

A reversed-phase high-performance liquid chromatographic (RP-HPLC) method for the measurement of methylprednisolone hemisuccinate (MPHS) and its metabolites methylprednisolone (MP), 20-alpha- (20a-HMP), and 20-beta-hydroxymethylprednisolone (20b-HMP) in urine is described. The metabolites were extracted from urine samples using Extrelut columns and eluted with ethylacetate. The mobile phase for RP-HPLC comprised methanol:citrate buffer:tetrahydrofuran (30:65:5, vol/vol/vol) with UV detection at 251 nm. Fractions were collected, pooled and the metabolites present were identified by gas chromatography-mass spectrometry and normal-phase HPLC (NP-HPLC). By RP-HPLC 30 +/- 7.3% (mean +/- 1 SD) of the dose was detected in the 0-24 h urine sample following a 1 g MPHS infusion to patients with rheumatoid arthritis; MPHS contributed 9.9 +/- 5.0%, MP 12.1 +/- 2.9%, 20a-HMP 7.8 +/- 2.2%, and 20b-HMP 1.0 +/- 0.3%, respectively. A further 1.0 +/- 0.9% of the administered dose was detected in urine collected 24-48 h postinfusion.

Pharmacokinetics of high-dose methylprednisolone in children

Disposition of methylprednisolone was characterized in 11 children receiving the high-dose therapy (26.0 mg/kg on average). After intravenous infusion, methylprednisolone hemisuccinate was rapidly converted to methylprednisolone with a half-life of about 20 min. Methylprednisolone in serum, eliminated monoexponentially in 8 patients and biexponentially in the remaining three, had the mean residence time of about 3 h, and a terminal half-life of 2.5 h. The volume of distribution at steady state, and the clearance were 1.3 liters/kg and 0.5 liters/kg/h, respectively. Although these average pharmacokinetic parameters were comparable to those determined in other studies with conventional low doses, the clearance values in our data were characterized by 5-fold interindividual difference, suggesting large variations in exposures to methylprednisolone among children on the high-dose pulse therapy.

Simultaneous determination of methylprednisolone and methylprednisolone 21-[8-[methyl-(2-sulfoethyl)amino]-8-oxooctanoate] sodium salt in human urine by high-performance liquid chromatography with ultraviolet detection

A reversed-phase high-performance liquid chromatographic assay 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-oxooctanoate] sodium salt (MPSO) in human urine following therapeutic doses in humans. The assay procedure involves stabilization of urine samples by addition of disodium ethylenediaminetetraacetic acid (Na2EDTA) and ion-pair extractions of MPSO using tetraethylammonium chloride (TEACl) as the counter ion. 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 microliters of mobile phase and chromatographed on an IBM C18 reversed-phase column (5 microns). The mobile phase was a mixture of water-acetonitrile-isopropanol (71.2:18.8:10.0, v/v) containing 75 microliters of 0.1 M hydrochloric acid and 0.450 g of TEACl per liter. Propyl p-hydroxybenzoate was used as an internal standard. The extraction efficiencies of MP and MPSO were greater than 90% using the ion-pairing agent TEACl. The chromatographic responses were linear up to about 200 micrograms/ml for MP and 80 micrograms/ml for MPSO and had sufficient precision and accuracy to provide quantitative data from human urine. The assay detection limit was about 8 ng/ml for MP and 25 ng/ml for MPSO in human urine. Stability studies in urine indicated that without Na2EDTA stabilization and at room temperature, rapid degradation of MPSO occurred in urine. Addition of EDTA to the urine specimen and storage at -70 degrees C increased the stability of MPSO, and little or no degradation was observed in urine stored for more than 60 days. The method has been used in the simultaneous determination of MP and MPSO in urine specimens obtained from a single-dose tolerance study of MPSO in normal male volunteers.

Comparative pharmacokinetics of methylprednisolone phosphate and hemisuccinate in high doses

The pharmacokinetics of methylprednisolone and two methylprednisolone esters, the phosphate and the hemisuccinate, were investigated after intravenous administration of the esters to 12 healthy male subjects in two different doses (250 and 1000 mg). Methylprednisolone was formed more rapidly from phosphate than from hemisuccinate. During the first 30 min methylprednisolone levels were three to four times higher after phosphate administration than after hemisuccinate. The mean residence time of the hemisuccinate was significantly longer and the total-body clearance lower than those of the phosphate. Whereas very little of the phosphate (mean, 1.7%) was eliminated unchanged into the urine, there were significant amounts of hemisuccinate (mean, 14.7%) excreted renally and therefore not bioavailable. Methylprednisolone saliva levels paralleled plasma levels; the average saliva/plasma ratio was 0.22. Neither phosphate nor hemisuccinate could be detected in saliva. An average of 7.2% of the administered dose was eliminated in the form of methylprednisolone in urine. Renal clearance was 24 ml/min and not dose or prodrug dependent. For both doses endogenous hydrocortisone levels were lowered after 24 hr. For the 1000-mg dose the depression was still significant after 48 hr. The results indicate that methylprednisolone phosphate results in a faster and more efficient conversion to its active form, methylprednisolone, than methylprednisolone hemisuccinate.

Determination of methylprednisolone metabolites in human urine by gas chromatography-mass spectrometry

Methylprednisolone and its metabolites were studied as their methoxyamine-trimethylsilyl derivatives by means of capillary gas chromatography-mass spectrometry. The expected unchanged drug and 11-keto and 20-hydroxy metabolites were found in human urine. The typical metabolites are 6,7-dehydro analogues of the above-mentioned compounds. Characteristic gas chromatographic profiles of urine steroids were obtained. Retention indices and m/z values are presented for methylprednisolone and its main metabolites.

Steroid administration and nitrogen excretion in the head-injured patient

The effect of steroid administration on metabolic rate and nitrogen excretion was examined in 20 head-injured patients alternately assigned to receive either methylprednisolone for 14 days or no steroid treatment. Although metabolic rate, caloric intake, and nitrogen intake were not different between the two groups, the patients who received steroids had a 30% higher excretion of nitrogen during the first 6 days after injury than did the patients not receiving steroids. All patients had an increase in nitrogen excretion through the 2nd week, peaking on Day 11. By Day 21 after injury, the patients had an average cumulative nitrogen loss of 162 gm and had lost an average of 5 kg body weight regardless of whether they had received steroids. Serum albumin levels decreased in the steroid-treated patients but returned to nearly normal by Day 21 in the untreated group. Immunosuppression, evidenced by a lower initial total lymphocyte count and a higher incidence of infections, was present in the steroid group; hyperglycemia requiring insulin treatment was more common in those patients.

Rapid method for the measurement of methylprednisolone and its hemisuccinate in plasma and urine following "pulse therapy" by high-performance liquid chromatography

A rapid method for the measurement of methylprednisolone and its 21-hemisuccinate ester in plasma and urine following high dose pulse therapy is described. The drugs were extracted using Extrelut columns, eluted with ethyl acetate which was evaporated to dryness and the residue was reconstituted in chromatographic mobile phase. High-performance liquid chromatography was performed on a reversed-phase column using a mobile phase of acetonitrile-acetate buffer with detection at 251 nm. No interference from any drugs or endogenous compounds has been observed. The method has been used to analyse over 200 plasma and 150 urine samples from patients with rheumatoid disease or renal failure who have received high dose methylprednisolone hemisuccinate infusions.

Identification of metabolites of methylprednisolone in equine urine

Methylprednisolone and three metabolites, 17,21-dihydroxy-6 alpha-methyl-1,4-pregnadiene-3,11,20-trione, 6 alpha-methyl-17,20 beta,21-trihydroxy-1,4-pregnadiene-3,11-dione, and 6 alpha-methyl-11 beta,17,20 beta,21-tetrahydroxy-1,4-pregnadien-3-one were detected in equine urine after intraarticular administration of methylprednisolone acetate. All four compounds were excreted both in the unconjugated form and as glucuronic acid conjugates. They were identified by comparing data obtained from analyses by high performance liquid chromatography, thin-layer chromatography, ultraviolet spectroscopy and gas chromatography/mass spectrometry to those of the synthesized standards. The presence of trace amounts of a fourth metabolite, 6 alpha-methyl-11 beta,17,20 alpha,21-tetrahydroxy-1,4-pregnadien-3-one, was indicated by high performance liquid chromatography but confirmation has not been attained by the other methods.

High-dose methylprednisolone sodium succinate (pulse therapy) in the treatment of renal disease: plasma and urine concentrations

Methylprednisolone hemisuccinate (MPS) and methylprednisolone (MP) concentrations in plasma and urine were monitored in renal transplant and glomerulonephritis patients who were given i.v. infusions of 0.5 g or 1 g of MPS. A marked individual variation of peak plasma levels of both MPS and MP was observed after the same dose and MPS disappeared from plasma more rapidly than MP. Their clearances from the circulation, however, did not appear to be significantly influenced by the peak plasma levels of the drug, creatinine clearance, administration of previous pulses of MPS or the urinary excretion of unconjugated MPS and MP. Even in patients with profoundly reduced renal function, no accumulation of the drug was apparent when repeated doses of MPS were administered at 48-h intervals.