Determination of midazolam and two of its metabolites in human plasma by high-performance liquid chromatography

Validation of a HPLC method for quantification of midazolam in rat plasma: Application during a Maytenus ilicifolia-drug interaction study

Midazolam (MDZ) is routinely employed as a marker compound of cytochrome P450 3A (CYP3A) activity. Despite the many HPLC-UV methods described to quantify MDZ in plasma, all of them use acetonitrile (ACN) or a mixture of methanol-isopropanol as organic solvent of the mobile phase. Since the ACN shortage in 2008, efforts have been made to replace this solvent during HPLC analysis. A simple, sensitive, accurate and repeatable HPLC-UV method (220 nm) was developed and validated to quantify MDZ in rat plasma using methanol instead. The method was applied during a herb-drug interaction study involving Maytenus ilicifolia, a Brazilian folk medicine used to treat gastric disorders. Plasma samples were alkalinized and MDZ plus alprazolam (internal standard) were extracted with diethyl ether. After solvent removal, the residue was reconstituted with methanol-water (1:1). The analyte was eluted throughout a C₁₈ column using sodium acetate buffer (10 mm, pH 7.4)-methanol (40:60, v/v). The precision at the lower limit of quantification never exceeded 19.40%, and 13.86% at the higher levels of quality control standards, whereas the accuracy ranged from -19.81 to 14.33%. The analytical curve was linear from 50 to 2,000 ng/ml. The activity of the hepatic CYP3A enzymes was not affected by the extract.

A new validated HPLC method for the determination of sulforaphane: application to study pharmacokinetics of sulforaphane in rats

A simple, accurate and reproducible high-performance liquid chromatography (HPLC) method has been developed and validated for the quantification of sulforaphane (SF) in rat plasma. The method involves a simple liquid-liquid extraction procedure to extract both SF and 7-hyrdoxycoumarin, the internal standard. The chromatographic analysis was achieved on a Shimadzu LC 20A HPLC system equipped with a Zorbax Eclipse XDB C18 column and an isocratic mobile phase consisting of 10 mm KH2 PO4 (pH 4.5) and acetonitrile HPLC grade (40:60, v/v) run at a flow rate of 1 mL/min for 10 min. The UV detection wavelength was set at 202 nm. The method exhibited good linearity (R(2) > 0.999) over the assayed concentration range (0.05-2 μg/mL) and demonstrated good intra- and inter-day precision and accuracy (relative standard deviations and the deviation from predicted values were <15%). This method was also successfully applied for studying the pharmacokinetics of SF in spontaneously hypertensive rats following single oral dietary doses of SF. The pharmacokinetics of SF show linear behavior at the dose range investigated in this study. Copyright © 2015 John Wiley & Sons, Ltd.

In vitro inhibitory effects of Wen-pi-tang-Hab-Wu-ling-san on human cytochrome P450 isoforms

WHAT IS KNOWN AND OBJECTIVE

Although Wen-pi-tang-Hab-Wu-ling-san (WHW), an oriental herbal medicine, has been prescribed for the treatment of chronic renal failure (CRF) in Korean clinics, no studies regarding WHW-drug interactions had been reported. The purpose of this study was to evaluate the possibility that WHW inhibits the catalytic activities of major cytochrome P450 (CYP) isoforms.

METHODS

The abilities of various WHW extracts to inhibit phenacetin O-de-ethylation (CYP1A2), tolbutamide 4-methylhydroxylation (CYP2C9), omeprazole 4'-hydroxylation (CYP2C19), dextromethorphan O-demethylation (CYP2D6), chlorzoxazone 6-hydroxylation (CYP2E1) and midazolam 1-hydroxylation (CYP3A4) were assessed using human liver microsomes.

RESULTS AND DISCUSSION

WHW extract at concentrations up to 100 μm showed negligible inhibition of the six CYP isoforms tested (CYP1A2, CYP2C9, CYP2C19, CYP2D6, CYP2E1 and CYP3A4), with apparent IC(50) values (concentration of the inhibitor causing 50% inhibition of the original enzyme activity) of 817.5, 601.6, 521.7, 310.2, 342.8 and 487.0 μg/mL, respectively.

WHAT IS NEW AND CONCLUSION

Our in vitro findings suggest that WHW extract at concentrations corresponding to a clinically recommended dosage range has no notable inhibitory effects on CYP isoforms. Therefore, we believe that WHW extract may be free of drug-herb interactions when co-administered with other medicines. However, in vivo human studies are needed to confirm these results.

Blood concentrations of midazolam in status epilepticus using an appropriate condition of HPLC

BACKGROUND

The aim of the present study was to determine an index to evaluate the efficacy and safety of midazolam (MDZ) to treat status epilepticus (SE). An original system was therefore developed to measure blood concentrations of MDZ and 1-hydroxymidazolam (1-OHMDZ) as the main metabolite on high-performance liquid chromatography.

METHODS

This system was established through inspection of chromatograms, calibration curves and coefficient of correlations of MDZ. The clinical course of 11 SE patients, ranging from 4 months to 10 years of age, are described. These patients were treated with MDZ and measured at each blood concentration of MDZ. Moreover, patients were evaluated on cranial computed tomography and magnetic resonance imaging and video electroencephalogram (EEG), and it was determined that their seizures disappeared in accordance with the disappearance of convulsions and interictal EEG findings.

RESULTS

Reproducibility was good with this system. The standard curves of MDZ and 1-OHMDZ were almost straight, and the correlation coefficients of MDZ and 1-OHMDZ were r = 0.9999 and r = 0.9998, respectively. The convulsions in nine of 11 SE patients disappeared without side-effects and the blood concentrations of MDZ in all the patients were measured. The mean peak blood concentrations of MDZ and 1-OHMDZ were higher than those reported in other studies.

CONCLUSIONS

The clinical utility of this system has been demonstrated. An index to evaluate the efficacy and safety of MDZ is necessary, and MDZ blood concentrations measured on the present original precise measuring system could help in establishing a plan to successfully treat SE.

Chemical stability of midazolam injection by high performance liquid chromatography

The chemical stability of midazolam hydrochloride injection, undiluted or diluted with dextrose sterile solution, was studied at different storage conditions by LC. The study was performed at room temperature (23 +/- 2 degrees C) under light exposure and light protection, +8 +/- 1 degrees C and -20 +/- 0.5 degrees C, in glass and plastic containers over 14 days with midazolam hydrochloride injection, undiluted or diluted with 5% dextrose sterile solution. Chromatographic separation was carried out on a RP-18(e) column, using a mobile phase consisting of ACN-phosphate buffer (pH 3.3; 0.1 M) (30:70 v/v) at a flow rate of 1.0 mL/min and UV detection at 220 nm. The concentrations of all samples remained greater than 90% of the original concentration. The chromatographic assay exhibited an adequate linearity (r(2) >0.999), selectivity, precision (RSD <3.1), and accuracy (recoveries from 100.46 to 101.40%). Injectable midazolam hydrochloride was chemically stable in all conditions that were studied.

HPLC determination of midazolam and its three hydroxy metabolites in perfusion medium and plasma from rats

A new, simple, rapid, sensitive, and repeatable isocratic reverse-phase HPLC method was developed and validated for simultaneous determination of midazolam and its main three hydroxylated metabolites, i.e. 1'-hydroxymidazolam, 4-hydroxymidazolam, and 1',4-dihydroxymidazolam in rat liver perfusate and also plasma. Diazepam was used as an internal standard to ensure precision and accuracy of this method. Analytes were extracted from alkalinized samples into diethyl ether using single-step liquid-liquid extraction. A C18 analytical column and a mobile phase composed of acetonitrile and sodium acetate buffer were used for the chromatographic separation with UV detection. Limits of detection varied between 7.9 and 19.6 microg/L for midazolam and its hydroxy metabolites. The overall recovery for the analytes exceeded 92%, for concentrations twice the limits of detection. The intra- and inter-day precision at three different concentrations never exceeded 8 and 11% variation, respectively. This method is applicable for modeling and description of possible pharmacological interactions on rat (CYP3A1/2) or human (CYP3A4/5) cytochrome P450 enzymes.

Simultaneous determination of midazolam and 1′-hydroxymidazolam in human plasma by liquid chromatography with tandem mass spectrometry

A sensitive and simple liquid chromatography-tandem mass spectrometry method for the determination of midazolam and 1'-hydroxymidazolam in human plasma has been developed and validated with a dynamic range of 0.1-250 ng/mL. The analysis was based on semi-automated liquid-liquid extraction followed by evaporation of the extraction solvent, reconstitution and chromatography on a reversed-phase C(18) column. The mobile phase consists of 5 mm ammonium acetate and methanol and runs in gradient at a flow rate of 0.25 mL/min with column temperature of approximately 20 degrees C. The entire column effluent was transferred into the LC-MS/MS interface operated in positive electrospray ionization mode. The chromatographic run time was 4.3 min per injection, with retention times for midazolam, 1'-hydroxymidazolaml and the internal standard, triazolam, of 2.5, 2.3 and 2.1 min, respectively. The intra-day and inter-day precision (RSD %) and accuracy (bias %) of the quality control samples were <15.0% and within +/-13%, respectively. The current method has been applied to a clinical drug-drug interaction study in human.

Determination of midazolam and its hydroxy metabolites in human plasma and oral fluid by liquid chromatography/electrospray ionization ion trap tandem mass spectrometry

Midazolam (MDZ), a short-acting benzodiazepine, is a widely accepted probe drug for CYP3A phenotyping. Published methods for its analysis have used either therapeutic doses of MDZ, or, if employing lower doses, were mostly unable to quantify the two hydroxy metabolites. In the present study, a sensitive and specific liquid chromatography/electrospray ionization tandem mass spectrometry method was developed and validated for the quantitative determination of MDZ and two of its metabolites (1'-hydroxymidazolam (1'-OHMDZ) and 4-hydroxymidazolam (4-OHMDZ)) in human plasma and oral fluid. After liquid-liquid extraction with hexane/dichloromethane (73:27, v/v), the analytes were separated on a Luna C18(2) (100 x 2.1 mm) analytical column using gradient elution. Detection was achieved using tandem mass spectrometry on an ion trap mass spectrometer. Midazolam-d6 was used as internal standard for quantification. The calibration curves were linear (R2 >0.998) between 0.05 and 20 ng/mL for MDZ and both metabolites in both matrices. Using 1 mL samples, the limit of detection was 0.025 ng/mL and the limit of quantification was 0.05 ng/mL for MDZ and the hydroxy metabolites in both matrices. Intra- and inter-day accuracies, determined at three different concentrations, were between 92.1 and 102.3% and the corresponding coefficients of variation were <7.3%. The average recoveries were 90.6%, 86.7% and 79.0% for MDZ, 1'-OHMDZ and 4-OHMDZ in plasma and 95.3%, 96.6% and 86.8% for MDZ, 1'-OHMDZ and 4-OHMDZ, respectively, in oral fluid. The method was successfully applied to a pharmacokinetic study, showing that MDZ and its hydroxy metabolites can be determined precisely in in vivo samples obtained following a single oral or intravenous dose of 2 mg MDZ. The method appears to be useful for CYP3A phenotyping in plasma using sub-therapeutic MDZ doses, but larger studies are needed to test this assumption.

Determination of midazolam and its major metabolite 1'-hydroxymidazolam by high-performance liquid chromatography-electrospray mass spectrometry in plasma from children

We have developed a sensitive, selective and reproducible reversed-phase high-performance liquid chromatography method coupled with electrospray ionization mass spectrometry (HPLC-ESI-MS) for the simultaneous quantification of midazolam (MDZ) and its major metabolite, 1'-hydroxymidazolam (1'-OHM) in a small volume (200 microl) of human plasma. Midazolam, 1'-OHM and 1'-chlordiazepoxide (internal standard) were extracted from alkalinised (pH 9.5) spiked and clinical plasma samples using a single step liquid-liquid extraction with 1-chlorobutane. The chromatographic separation was performed on a reversed-phase HyPURITY Elite C18 (5 microm particle size; 100 mm x 2.1mm i.d.) analytical column using an acidic (pH 2.8) mobile phase (water-acetonitrile; 75:25% (v/v) containing formic acid (0.1%, v/v)) delivered at a flow-rate of 200 microl/min. The mass spectrometer was operated in the positive ion mode at the protonated-molecular ions [M+l]+ of parent drug and metabolite. Calibration curves in spiked plasma were linear (r2 > or = 0.99) from 15 to 600 ng/ml (MDZ) and 5-200 ng/ml (1'-OHM). The limits of detection and quantification were 2 and 5 ng/ml, respectively, for both MDZ and 1'-OHM. The mean relative recoveries at 40 and 600 ng/ml (MDZ) were 79.4+/-3.1% (n = 6) and 84.2+/-4.7% (n = 8), respectively; for 1'-OHM at 30 and 200 ng/ml the values were 89.9+/-7.2% (n = 6) and 86.9+/-5.6% (n = 8), respectively. The intra-assay and inter-assay coefficients of variation (CVs) for MDZ were less than 8%, and for 1'-OHM were less than 13%. There was no interference from other commonly used antimalarials, antipyretic drugs and antibiotics. The method was successfully applied to a pharmacokinetic study of MDZ and 1'-OHM in children with severe malaria and convulsions following administration of MDZ either intravenously (i.v.) or intramuscularly (i.m.).

Sensitive determination of midazolam and 1′-hydroxymidazolam in plasma by liquid–liquid extraction and column-switching liquid chromatography with ultraviolet absorbance detection and its application for measuring CYP3A activity

This manuscript described a new sensitive determination of midazolam and its metabolite 1'-hydroxymidazolam by automated column-switching high-performance liquid chromatography. The test compounds were extracted from 2 ml of plasma using chloroform-hexane (30:70, v/v) and the extract was injected into a column I (TSK-PW precolumn, 10 microm, 35 mm x 4.6 mm i.d.) for clean-up and column II (C18 STR ODS-II analytical column (5 microm, 150 mm x 4.6 mm i.d.) for separation. The mobile phase for separation consisted of phosphate buffer (0.02 M, pH 4.6), perchloric acid (60%) and acetonitrile (57.9:0.1:42, v/v/v) and was delivered at a flow-rate of 0.6 ml/min. The peak was detected using a UV detector set at 254 nm. The method was validated for the concentration range 0.3-100 ng/ml, and good linearity (r > 0.998) was confirmed. Intra- and inter-day coefficient variations for midazolam and 1'-hydroxymidazolam were less than 8.5 and 6.1%, respectively, at the concentrations of 0.5, 5 and 50 ng/ml for the test compounds. Relative errors ranged from -14 to 6% and mean recoveries were 78-85%. The limit of quantification was 0.5 ng/ml for each compound. This method was sensitive enough for pharmacokinetic studies measuring CYP3A activity in human volunteers following an intravenous (1 mg) and a single-oral administration (2 mg) of a subtherapeutic midazolam dose.

A sensitive HPLC-MS-MS assay for quantitative determination of midazolam in dog plasma

The clinical pharmacokinetics of midazolam have been extensively studied, due to its high clearance by CYP3A4 and sensitivity to drug-drug interactions. In order to investigate the potential to model drug-drug interactions with midazolam in the dog, a selective and sensitive high performance liquid chromatography-tandem mass spectroscopy (HPLC-MS-MS) method has been developed, with sufficient sensitivity to allow analysis of dog plasma samples generated following administration of a clinically relevant dose. The method involves extraction of midazolam and internal standard (flunitrazepam) from dog plasma, using 96-well Oasis MCX solid phase extraction plates. The assay has been validated over a concentration range of 0.1-10 ng/ml and its specificity, accuracy and precision demonstrated. The relative bias of the assay was within +/-15% for all standards with intra- and inter-assay precision (coefficient of variation-%CV) of less than 15%. The assay was applied to the analysis of plasma samples (0.2 ml), generated following intravenous or oral administration of midazolam to male beagle dogs, at a dose level of 0.05 mg/kg, and pharmacokinetic parameters were derived from the resulting data.

In-process control of midazolam synthesis by HPLC

A high-performance liquid chromatographic assay coupled with UV detection (239 nm) has been developed for the determination of midazolam and its synthesis precursors. The separation of the analytes was performed on a Kromasil C8 column (15 cm x 4.6 mm i.d., 5 microm) at 30 degrees C. The mobile phase [ammonium chloride (pH 5.5, 1 g l(-1))-methanolacetonitrile (45:22:33, v/v/v)] was pumped at a flow-rate of 1.5 ml min(-1). This method is rapid (less than 11 min), sensitive (limit of detection (LOD) ranged between 0.05 and 0.5 mg l(-1)) and selective for the determination of midazolam, and it could be used for monitoring different synthetic routes.

Determination of midazolam and 1'-hydroxymidazolam by liquid chromatography-mass spectrometry in plasma of patients undergoing methadone maintenance treatment

A rapid, sensitive and selective LC-MS method was developed for the simultaneous determination of midazolam (MDZ) and 1'-hydroxymidazolam (1'-OHMDZ) in plasma taken from 54 patients undergoing methadone maintenance therapy, most of whom were multidrug users. Samples spiked with prazepam, the internal standard, and were extracted into diethyl ether. Compounds were separated on a Phenomenex Luna C(18) column and a mobile phase of acetonitrile-ammonium acetate buffer (10 mM, pH 4.7) (52:48, v/v) at a flow-rate of 1 ml/min. The limit of detection was 0.65 and 0.68 (ng/ml) for MDZ and 1'-OHMDZ, respectively. Within-day relative standard deviations were less than 8%.

Analysis of certain tranquilizers in biological fluids

A review with 282 references is presented that deals with the reported methods of analysis of phenothiazines, thioxanthenes, and benzodiazepine derivatives of pharmaceutical interest. The review includes the methods adapted in biological fluids.

Sensitive determination of midazolam and identification of its two metabolites in human body fluids by column-switching capillary high-performance liquid chromatography/fast atom bombardment-mass spectrometry

Midazolam is a benzodiazepine and is widely prescribed for preanesthesia or general anesthesia. Overdose or intoxication cases of midazolam have been reported. In Japan, smuggled midazolam tablets could be involved in some criminal cases. Midazolam and its two metabolites were extracted by the solid-phase extraction method using Bond Elut SCX cartridges. The compounds were analyzed by on-line capillary high-performance liquid chromatography/fast atom bombardment-mass spectrometry. Midazolam and its two metabolites were well separated on the chromatogram, and each mass spectra gave [M+H](+) ion as a base peak. Deuterium-labeled midazolam was synthesized as an internal standard; it has enabled precise and reproducible quantitation of midazolam in blood samples. The calibration curve showed excellent linearity in the range of 2-200 ng/ml in spiked serum. The detection limit was 300 pg/ml (signal-to-noise ratio=3). The whole blood and urine samples from the victim of a homicide case were analyzed, and the midazolam concentration in the whole blood was estimated to be 163 ng/ml. The present method should be useful in clinical and forensic toxicology, because of its high sensitivity and specificity.

Methods for the measurement of benzodiazepines in biological samples

A review of methods for the measurement of benzodiazepines in biological specimens published over the last five years is presented. A range of immunoassay procedures using EIA, ELISA, FPIA, agglutination or kinetic interaction of microparticles, or RIA methods are now available. Cross reactivities to benzodiazepines are variable such that no one kit will recognise all benzodiazepines and their relevant metabolites at concentrations likely to be encountered during therapeutic use. Prior hydrolysis of urine to convert glucuronide metabolites to immunoreactive substances improves detection limits for many benzodiazepines. Several radioreceptor assays have now been published and show good sensitivity and specificity to benzodiazepines and offer the advantage (over immunoassay) of being able to detect these drugs with equal sensitivity. Solvent extraction techniques using a variety of solvents were still popular and offer acceptable recoveries and lack of significant interference from other substances. A number of papers describing solid phase extraction procedures were also published. Direct injection of specimens into a HPLC column with back flushing were also successfully described. Seventy two chromatographic methods using HPLC, LC-MS, GC and GC-MS methods were reviewed. HPLC was able to achieve detection limits for many benzodiazepines using UV or DAD detection down to 1-2 ng/ml using 1-2 ml of urine or serum (blood). ECD detectors gave detection limits better than 1 ng/ml from 1 ml of specimen, which was an order of magnitude lower than for NPD. EI-MS offered similar sensitivity, whilst NCI-MS was capable of detection down to 0.1 ng/ml. Methods suitable for the separation of enantiomers of benzodiazepines have been described using HPLC. Electrokinetic micellar chromatography has also been shown to be capable of the analysis of benzodiazepines in urine.

Simultaneous determination of midazolam and its metabolites 1-hydroxymidazolam and 4-hydroxymidazolam in human serum using gas chromatography-mass spectrometry

A method for the quantitation of midazolam and its metabolites 1-hydroxymidazolam and 4-hydroxymidazolam from human serum capable of monitoring concentrations achieved under therapeutic conditions is presented. The substances were extracted under basic conditions with toluene and the hydroxy metabolites transformed to their tert-butyldimethylsilyl derivatives with N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide. The samples were measured by gas chromatography-mass spectrometry. The limits of detection are 0.2 ng ml(-1) for midazolam and 0.1 ng ml(-1) for 1-hydroxy- and 4-hydroxymidazolam. The coefficients of variation are 3.9% at 5 ng ml(-1) for midazolam, 6.7% at 2 ng ml(-1) for 1-hydroxymidazolam and 8.8% (22.2%) at 0.5 (0.2) ng ml(-1) for 4-hydroxymidazolam.

Determination of midazolam and its metabolites in serum microsamples by high-performance liquid chromatography and its application to pharmacokinetics in rats

A single-solvent extraction step high-performance liquid chromatographic method is described for quantitating midazolam and its two hydroxy metabolites in rat serum microsamples (50 microliters). The separation used a 2 mm I.D. reversed-phase Symmetry C18 column with an isocratic mobile phase consisting of methanol-acetonitrile-14.9 mM sodium acetate in water at pH 3.0 (10:23:67, v/v). The detection limit was 10 ng/ml for all the compounds using an ultraviolet detector operated at 230 nm. The method was used to study the pharmacokinetics of midazolam after an intravenous bolus dose (0.75 mg/kg).

Determination of midazolam and its unconjugated 1-hydroxy metabolite in human plasma by high-performance liquid chromatography

A selective and sensitive high-performance liquid chromatographic method for the analysis of midazolam and its unconjugated 1-hydroxy metabolite in plasma samples was developed. The compounds were extracted from plasma by a liquid-liquid extraction procedure with diethyl ether. Mean analytical recoveries were 87% and 86% at a concentration of 300 ng/ml for midazolam and 1-hydroxymidazolam, respectively, and the quantification limit was 2 ng/ml for a plasma volume of 1 ml. The separation of midazolam, 1-hydroxymidazolam and flurazepam (internal standard) was achieved on a Spherisorb 5 CN column using methanol-2(r)propanol (75:25, v/v) containing 0.015% perchloric acid at a flow-rate of 1.5 ml/min. The method is sensitive enough for monitoring midazolam and also the unconjugated form of the active metabolite in plasma during pharmacokinetic studies.