Concentration of methylprednisolone in the centrodistal joint after administration of methylprednisolone acetate in the tarsometatarsal joint

REASONS FOR PERFORMING STUDY

The centrodistal (CD) and tarsometatarsal (TMT) joints are often injected individually with a corticosteroid to resolve lameness caused by osteoarthritis (OA). There are no data available regarding diffusion of methylprednisolone (MP) from the TMT joint to the CD joint.

HYPOTHESIS

A therapeutic concentration of MP diffuses into the CD joint after methylprednisolone acetate (MPA) is administered into the TMT joint.

OBJECTIVE

To measure the concentration of MP in the CD joint after MPA was administered into the TMT joint.

METHODS

MPA was administered into a TMT joint of 16 horses. At different times, the ipsilateral CD joint of these horses was injected with a small amount of saline and recovered saline was measured for concentration of MP using high performance liquid chromatography.

RESULTS

Six hours after administration of MPA into the TMT joint, a therapeutic concentration of MP was found in all 10 CD joints sampled at this time.

CONCLUSIONS

Horses with pain arising from the distal 2 joints of the hock can be treated by administering MPA into the TMT joint alone.

POTENTIAL RELEVANCE

Administering MPA into the TMT joint only, to treat OA of the distal 2 hock joints, reduces the difficulties and risks associated with centesis of the CD joint.

[Using ultra performance liquid chromatography]

An analytical method based on ultra performance liquid chromatography has been developed for the simultaneous determination of 15 hormones (triamcinolone, hydrocortisone, prednisone, cortisone, 6a-methylprednisolone, betamethasone, dexamethasone, prednisolone acetate, hydrocortisone acetate, estriol, beta-estradiol, estrone, diethylstilbestrol, testosterone and progesterone) in cosmetics. Various cosmetic samples were extracted with methanol under ultrasonication, and then cleaned up by a Oasis HLB solid phase extraction cartridge. The 15 hormones were separated and detected within 6 min on a Waters ACQUITY UPLC BEH C18 column (1.7 microm, 2.1 mm x 50 mm) by gradient elution with acetonitrile and water system. In the range of 1-25 ng, the calibration curves of 15 hormones showed good linearity with the correlation coefficients larger than 0.9995. The mean recoveries at the three spiked levels (2, 10, 20 mg/kg) were 88.2%-102.4% with the relative standard deviations of 1.6%-7.4%.

Characterization of Methylprednisolone Esters of Hyaluronan in Aqueous Solution: Conformation and Aggregation Behavior

Methylprednisolone steroid esters of hyaluronan differing in degree of functionalization and molecular weight were investigated in aqueous solution. Conformation and aggregation phenomena were elucidated by means of circular dichroism, viscometry, rheology, and nuclear magnetic resonance, mainly by (1)H pulsed field gradient (PFG) NMR, which allows the determination of the diffusion coefficient of the species under investigation. The functionalization of hyaluronan with the steroid induces a reduction of the molecular volume, as a consequence of intramolecular hydrophobic interactions. For concentrated samples we have observed the coexistence of unimolecular collapsed chains and of aggregates, the latter disappearing upon dilution. The methylprednisolone ester of lower molecular weight hyaluronan has a larger molecular volume than its higher molecular weight analogue, even though still smaller than the underivatized polymer. This effect can be explained with the reduced flexibility of the polymer backbone probably impairing intramolecular interactions.

Micellar electrokinetic chromatography for simultaneous determination of six corticosteroids in commercial pharmaceuticals

We have developed a micellar electrokinetic chromatography (MEKC) method using bile salts for the simultaneous determination of six corticosteroids, including betamethasone, cortisone, prednisolone, 6alpha-methylprednisolone, triamcinolone, and prednisone. The separation was performed using borate buffer containing sodium cholate and sodium deoxycholate. Several parameters were studied, including bile salt concentrations, concentrations and pH of borate buffer, and analytical voltages. In method validation, calibration curves were linear over a range of 10-100 microM for each corticosteroid. The RSD (relative standard deviation) and RE (relative error) were all less than 5% for intra- and interday assays. The limit of detection of each analyte was 5 microM. The recoveries were greater than 95%. Application of this method for quality control of commercial tablets also proved to be feasible. All analytical values fall within the labeled amount of 90-110% for betamethasone and prednisolone, and of the labeled amount of 92.5-107.5% for 6alpha-methylprednisolone, as required by the United State Pharmacopeia 25 (USP 25).

Determination of CMC of sodium glucocorticides hemisuccinates by CE

The capillary zone electrophoresis (CZE) method was applied to the determination of the critical micelle concentration (CMC) and the anionic mobilities (mu(e)) for sodium glycocorticides hemisuccinates (Urbason solubile forte 1000, Hydrocortison 100 Rotexmedica, Prednisolut 100) in phosphate solution at pH 7.2. The CZE enables an efficient and very fast determination of parameters for characterizing physicochemical properties of micelles.

A high-performance liquid chromatography/tandem mass spectrometric screening method for eight synthetic corticosteroids in bovine feces and the simultaneous differentiation between dexamethasone and betamethasone

A screening method was developed to monitor the illegal use of synthetic corticosteroids in cattle. Diethyl ether extracts from spiked feces samples were cleaned-up by solid phase extraction followed by semipreparative reversed-phase chromatography (RPC). The fraction containing the corticosteroids was derivatized with ethoxyamine hydrochloride. The corresponding ethoximes were separated using silica-based C18 RPC and analyzed on-line in an ion trap mass spectrometer using atmospheric pressure positive chemical ionization. Ethoxime derivatives of dexamethasone and betamethasone were baseline resolved, allowing for the simultaneous mass spectrometric differentiation of both epimers in bovine feces by conventional non-chiral chromatography. At the lowest level tested (1 micro g/kg), corticosteroids (except triamcinolone) could be identified in compliance with the recent European criteria for residue identification. The quantitative performance of the method was best at residue levels > or = 2 micro g/kg.

Collision-induced dissociation of corticosteroids in electrospray tandem mass spectrometry and development of a screening method by high performance liquid chromatography/tandem mass spectrometry

A screening method based on liquid chromatography/electrospray tandem mass spectrometry was developed in order to control the illegal use of corticosteroids as growth promoters in cattle. The objective was the detection of low residue levels of corticosteroids or metabolites in biological matrices. Relative to other studies published on this subject, the present work focused on enhancing specificity and sensitivity. Firstly, fragmentation of corticosteroids by collision-induced dissociation was studied. In positive mode, the losses of H(2)O for each hydroxyl group fixed on the molecule, as well as the loss of HF or HCl for halogenated compounds, were observed. For higher collision energy, fragmentations in the B, C and D rings were induced. The negative mode was found to be more specific, inducing a cleavage of the C(20)-C(21) bond with concomitant loss of formaldehyde (CH(2)O). Secondly, three acquisition methods in the negative mode were studied and evaluated, recorded signals being the parent ion [M + acetate](-) and the two daughter ions, [M - H](-) and [M - H - CH(2)O](-). For dexamethasone, MS/MS instrumental detection limits of fragment ion and neutral loss scans, and of multiple reaction monitoring (MRM), were 250, 20 and 5 pg injected, respectively. The MRM method was then evaluated with the objective of use for the detection of corticosteroid residues in biological samples (urine, hair, muscle) and for a metabolism study.

Simultaneous analysis of dextran-methylprednisolone succinate, methylprednisolone succinate, and methylprednisolone by size-exclusion chromatography

An analytical HPLC method is reported for simultaneous measurement of low (1.0-100 microg ml(-1)) concentrations of dextran-methylprednisolone succinate (DEX-MPS) and its degradation products methylprednisolone hemisuccinate (MPS) and methylprednisolone (MP). The analytes were detected at 250 nm after resolution using a size exclusion column with a mobile phase of KH2PO4 (10 mM): acetonitrile (3:1) and a flow rate of 1 ml min(-1). The resolution of MP and MPS peaks was substantially affected by the pH of the mobile phase; while MP and MPS co-eluted at pH 3.4, they were baseline-resolved at pH > or = 5. Linear relationships (r > or = 0.997) were found between the detector response and the concentrations of the analytes (1.0-100 microg ml(-1) for MP and MPS and 2.5-100 microg ml(-1) for DEX-MPS). Intra- and inter-run error (< 13%) and precision (CV of < or = 6%) data indicated that the assay could accurately and precisely quantitate all three components in the examined concentration range. The application of the assay to determination of degree of substitution, purity, and stability of DEX-MPS was also demonstrated.

Plasma, urine, and synovial fluid disposition of methylprednisolone acetate and isoflupredone acetate after intra-articular administration in horses

OBJECTIVE--To document plasma, urine, and synovial fluid disposition of 2 common intra-articularly administered steroid preparations, methylprednisolone acetate (MPA) and isoflupredone acetate (IPA). DESIGN--Descriptive investigation. SAMPLE POPULATION--100 mg of MPA or 4 mg of IPA was administered to 2 groups of 4 healthy sound radiographically normal female horses. PROCEDURE--Blood samples were collected at time 0 (before) and 2, 4, 6, 8, 10, 12, 24, 36, 48, 72, and 96 hours after administration of the designated steroid. Complete urine collection for measurement of designated steroid was accomplished by use of occluding 28-F balloon catheters. Synovial fluid samples were aseptically aspirated from the injected and contralateral uninjected tarsocrural joint at time 0 and 8, 24, 48, 240, and 672 hours after administration of the designated steroid. All samples were screened by ELISA to detect parent drug or metabolite equivalent, with a sensitivity of 2.5 ng/ml for MPA and 0.1 ng/ml for IPA. If drug was detected by ELISA in the plasma or synovial fluid, the samples were further quantified and specified, using HPLC with a lower limit of quantification (10 ng/ml). RESULTS--Between 2 and 12 hours after administration, plasma contained < 10 ng of MPA or IPA/ml (parent drug or metabolite equivalent), as intermittently detected by ELISA. Parent drug or metabolite equivalent was detected in the urine for 24 and 72 hours after injection of IPA and MPA, respectively. Synovial fluid from the contralateral joint contained no detectable MPA or IPA at any sample collection time. Median half-life for MPA, as detected by HPLC, was 10.3 hours (range, 6.1 to 10.6) in the synovial space. Median half-life for methylprednisolone, as detected by HPLC, was 10.4 (range, 9.9 to 32.1) hours. CONCLUSIONS--Both steroids appeared to be rapidly hydrolyzed to their respective ester forms, as detected by HPLC. The ELISA appeared to be a useful screening tool for detection of corticosteroids in this variety of body fluids.

Capillary reversed-phase high-performance liquid chromatographic determination of acetyl-methylprednisolone in feline spinal cord

Capillary reversed-phase high-performance liquid chromatography (RP-HPLC) was used to determine acetylmethylprednisolone (A-MP) that had been administered to feline spinal cord tissue. The method used a 300 mm x 0.32 mm I.D. packed capillary octadecylsilyl (ODS) column and an isocratic mobile phase of 40 mM triethylamine formate (TEAF, pH 3.2)-acetonitrile (50:50, v:v). The chromatographic behavior of A-MP was evaluated with respect to peak-area and peak-height by varying the A-MP concentration (12-190 microM) with a fixed injection volume (1 microliter), and by varying the injection volume (1-10 microliter) with a fixed concentration (12 microM) of A-MP. The limit of detection (signal-to-noise ratio, 3:1) was 250 pg (600 fmol) of synthetic A-MP. Various amounts of A-MP directly spiked into feline spinal cord segments were solvent extracted, separated, and plotted against peak-area (r2 = 1.00). Background tissue without A-MP gives minimal (< 1%) interference at 243 nm. The method also detects exogenous A-MP that was administered into feline spinal cord via an intrathecal injection. Furthermore, the presence of A-MP was confirmed via its molecular ion and corresponding product ions that were obtained by fast-atom bombardment tandem mass spectrometry (FAB-MS-MS).

Purity evaluation of 6 alpha-methylprednisolone acetate by HPLC

A high-performance liquid chromatographic method is described for the analysis and identification of related impurities in pharmaceutical-grade 6 alpha-methylprednisolone acetate (MPA). Eight MPA impurities derived from synthesis and/or degradation processes were identified. The method is compared to other analytical procedures recently proposed for the European Pharmacopoeia.

High-performance liquid chromatography separation and quantitation of methylprednisolone from rat brain

A sensitive, reliable method for the extraction, separation, and quantitation of methylprednisolone from rat brain is reported. The method can accurately quantitate methylprednisolone levels between 9.8 and 2500 ng/injection using a two-step HPLC separation and monitoring absorbance at 254 nm. A 90% extraction recovery of methylprednisolone (interday variation of 9.0% and an intraday variation of 0.0 to 7.7%) from rat cortex was obtained with a double extraction method using low toxicity solvents. These solvents are known to quantitatively extract the neutral lipids and phospholipids from brain. Combined with the ability to separate the neutral lipid and methylprednisolone fractions for further separation, and the ability to separate all phospholipid classes in the first run, this method offers great utility combined with the reliable, high extraction recovery and sensitive quantitation of methylprednisolone.

Two chromatographic methods for the determination of corticosteroids in human biological fluids: pharmacokinetic applications

Two techniques, high-performance liquid chromatography (HPLC) and quantitative high-performance thin-layer chromatography coupled with densitometry (HPTLC), were developed for the determination of prednisolone (PL), methylprednisolone (MP), and methylprednisolone sodium succinate (MPSS) in human plasma, saliva, and urine. The HPLC and HPTLC methods shared a single and simple step of an organic extraction procedure and separation of steroids using a normal-phase column or HPTLC plate. The methods allow simultaneous measurement of endogenous cortisol in plasma following the administration of PL and MP. The calibration curves of steroids in all biological fluids were linear over a wide range of concentrations of PL and MP in all biological fluids (0.025-4 micrograms/mL). The limit of detection of both assays for PL and MP was 10 ng/mL in plasma and saliva and 25 ng/mL in urine, and of MPSS was 50 ng/mL in plasma. Both methods were reproducible with an inter- and intra-assay coefficient of variation of less than 10% for all steroids over a wide range of concentrations in all biological fluids. No interference from endogenous steroids was found. The presented methods are simple, rapid, specific, sensitive, reproducible, and economical for the pharmacokinetic study of these steroids. The application of these methods for the pharmacokinetic study of both MP and PL in vivo and the in vitro hydrolysis of MPSS is discussed.

Determination of methylprednisolone in rat tissue by high-performance liquid chromatography

Methylprednisolone was determined in various types of rat tissue following an intravenous injection of methylprednisolone sodium succinate. Two modes of tissue work-up were investigated: digestion with subtilisin Carlsberg, a proteolytic enzyme, and homogenization with methanol. The final determination was by reversed-phase high-performance liquid chromatography with dexamethasone as internal standard. The extraction yields of methylprednisolone and dexamethasone from tissue homogenate and the extraction yield of methylprednisolone after incubation with viable tissue were determined. The experiments show that methylprednisolone and the internal standard are extracted in similar yields from tissue homogenates and that methylprednisolone can be recovered in a good yield after incubation with viable tissue, provided that the tissue does not have a high metabolic activity. There was a good agreement between the analytical results from the two different types of tissue work-up. The method of analysis proved feasible for pharmacokinetic work.

Sustained release of a corticosteroid using polymeric implants

An effective sustained release method of drug administration, using methylprednisolone incorporated into acrylic bone cement, has been developed. The effect of this form of treatment on peripheral blood leukocytes, lymphoid tissue weight and the inflammatory response has been evaluated. This mode of methylprednisolone administration was compared with conventional systemic therapy and was found to produce rapid and prolonged pharmacological effects at very low plasma levels of drug. A dose response relationship was established and we determined that, for a given quantity of drug, the level and duration of suppression was greater using sustained release therapy. The inflammatory response was also depressed using this mode of administration. These results, coupled with the commercial availability and existing clinical approval of SIMPLEX P bone cement, suggest that further development may lead to useful clinical protocols.

Carboxyl group catalysis of acyl transfer reactions in corticosteroid 17- and 21-monoesters

Succinate esters, although frequently employed as water-soluble prodrugs of poorly soluble parent drugs, are not sufficiently stable to allow long-term storage in solution. Intramolecular catalysis of ester hydrolysis by the terminal succinate carboxyl group is a contributing factor to this instability. Methylprednisolone 21-succinate has recently been reported to undergo both hydrolysis and 21 in equilibrium 17 acyl migration in aqueous solutions. Intramolecular catalysis by the terminal carboxyl group is seen in both reactions, but the catalytic mechanisms are not well understood. While acyl migration can only be catalyzed via the carboxyl group acting as a general acid or general base, hydrolysis may undergo either nucleophilic or general acid-base catalysis. To gain further insight into the catalytic mechanism, hydrolysis of methylprednisolone 21-succinate was carried out in aniline buffers to trap any succinic anhydride (as the anilide) that would form if the catalysis were nucleophilic. The nucleophilic mechanism was shown to account for only 15-20% of the overall catalysis. Comparisons of the rates of the intramolecularly catalyzed reactions of methylprednisolone 21- and 17-succinate were made with the same reactions of methylprednisolone 21- and 17-acetate catalyzed intermolecularly by acetate ion. Interestingly, intramolecular catalysis appears to favor acyl migration over hydrolysis. Hence, the hydrolysis of methylprednisolone 21-succinate is faster in basic solutions (pH greater than 7.4), while acyl migration becomes the dominant reaction in the catalyzed region of the pH profile between pH 3.6 and 7.4. Arguments are presented to account for these differences in catalytic efficiency in terms of the transition-state structures for the two reactions.

Analysis of cortisol, methylprednisolone, and methylprednisolone hemisuccinate. Absence of effects of troleandomycin on ester hydrolysis

A sensitive, selective, and reproducible high-performance liquid chromatographic assay for the simultaneous measurement of cortisol and methylprednisolone using dexamethasone as the internal standard is presented. Samples are extracted with methylene chloride, washed with sodium hydroxide and then water, and chromatographed on a microparticle silica gel column with ultraviolet detection at 254 nm. Sensitivity is greater than 10 ng/ml and the intra-day coefficient of variation is less than 5% for both steroids. The use of porcine liver esterase allows the quantitation of the hemisuccinate ester of methylprednisolone. This assay has been applied in pharmacokinetic studies including investigations of troleandomycin--methylprednisolone interactions. A typical plasma concentration--time profile for methylprednisolone and its ester prodrug is presented for one subject before and after receiving troleandomycin therapy. Although methylprednisolone elimination is reduced in the presence of troleandomycin therapy, there is no effect on the pharmacokinetics of methylprednisolone sodium succinate.

Kinetic study of USP blue tetrazolium assay with methylprednisolone, hydrocortisone, and their hemisuccinate esters by high-pressure liquid chromatography

The reactions of blue tetrazolium (I) with methylprednisolone and hydrocortisone and their hemisuccinate esters at ambient temperature under USP assay conditions in alcohol USP and in absolute alcohol were followed by high-pressure liquid chromatography (HPLC) and spectrophotometry. The disappearance of the ester and the increase and then decrease in the alcohol, as well as the formation of several reaction products with time, were observed by HPLC analysis. The reduction of I was observed spectrophotometrically. A sequential kinetic model was used to describe the overall reaction. The rate constants for the hydrolysis of the hemiester (k1), the reaction with I (k2), and the degradation of the parent steroid (k3) were determined by discrete kinetic experiments using HPLC. The following observations were made: (a) k1 is proportional to [H2O] and is the rate-limiting step, (b) k2 is about 100 times the value of k3 and (c) k2 for methylprednisolone is about the same as for hydrocortisone and appears to be independent of the concentration of water. With these rate constants, simulated time-concentration profiles for the reaction of the esters with I favorable compared with experimental data in alcohol USP and absolute alcohol. This study shows that the USP blue tetrazolium assay with these esters has potential for variability and is not stability indicating.