Linezolid: Pharmacokinetic and Pharmacodynamic Evaluation of Coadministration with Pseudoephedrine HCl, Phenylpropanolamine HCl, and Dextromethorphan HBr

Linezolid is a novel oxazolidinone antibiotic with mild reversible monoamine oxidase inhibitor (MAOI) activity. The potential for interaction with over-the-counter (OTC) medications requires quantification. The authors present data evaluating the pharmacokinetic and pharmacodynamic responses to coadministration of oral linezolid with sympathomimetics (pseudoephedrine and phenylpropanolamine) and a serotonin reuptake inhibitor (dextromethorphan). Following coadministration with linezolid, minimal but statistically significant increases were observed in pseudoephedrine and phenylpropanolamine plasma concentrations; a minimal but statistically significant decrease was observed in dextrorphan (the primary metabolite of dextromethorphan) plasma concentrations. Increased blood pressure (BP) was observed following the coadministration of linezolid with either pseudoephedrine or phenylpropanolamine; no significant effects were observed with dextromethorphan. None of these coadministered drugs had a significant effect on linezolid pharmacokinetics. Minimal numbers of adverse events were reported. Potentiation of sympathomimetic activity by linezolid was judged not to be clinically significant, but patients sensitive to the effects of increased BP due to predisposing factors should be treated cautiously. No restrictions are indicated for the coadministration of dextromethorphan and linezolid.

Nonuniform cardiac denervation observed by 11C-meta-hydroxyephedrine PET in 6-OHDA-treated monkeys

Parkinson's disease presents nonmotor complications such as autonomic dysfunction that do not respond to traditional anti-parkinsonian therapies. The lack of established preclinical monkey models of Parkinson's disease with cardiac dysfunction hampers development and testing of new treatments to alleviate or prevent this feature. This study aimed to assess the feasibility of developing a model of cardiac dysautonomia in nonhuman primates and preclinical evaluations tools. Five rhesus monkeys received intravenous injections of 6-hydroxydopamine (total dose: 50 mg/kg). The animals were evaluated before and after with a battery of tests, including positron emission tomography with the norepinephrine analog (11)C-meta-hydroxyephedrine. Imaging 1 week after neurotoxin treatment revealed nearly complete loss of specific radioligand uptake. Partial progressive recovery of cardiac uptake found between 1 and 10 weeks remained stable between 10 and 14 weeks. In all five animals, examination of the pattern of uptake (using Logan plot analysis to create distribution volume maps) revealed a persistent region-specific significant loss in the inferior wall of the left ventricle at 10 (P<0.001) and 14 weeks (P<0.01) relative to the anterior wall. Blood levels of dopamine, norepinephrine (P<0.05), epinephrine, and 3,4-dihydroxyphenylacetic acid (P<0.01) were notably decreased after 6-hydroxydopamine at all time points. These results demonstrate that systemic injection of 6-hydroxydopamine in nonhuman primates creates a nonuniform but reproducible pattern of cardiac denervation as well as a persistent loss of circulating catecholamines, supporting the use of this method to further develop a monkey model of cardiac dysautonomia.

Nano-desorption electrospray and kinetic method in chiral analysis of drugs in whole human blood samples

A home-made nano-desorption electrospray ionization (nano-DESI) device and the kinetic method were tested in chiral analysis of model clinical samples containing enantiomers of one of three pharmaceutically important compounds: dihydroxyphenylalanine (DOPA), ephedrine and ibuprofen. The initial evaluation of chiral systems was carried out by direct infusion of solution mixtures (analyte/central metal/chiral reference ligand) to a standard electrospray ionization (ESI) source. Cu(II) was used as a central metal for all analytes, L-phenylalanine was applied as a chiral reference ligand for DOPA, whereas L-tryptophan was used for the other two analytes. Then, the ESI source was substituted by a nano-DESI source and dried spots of 1 microL samples of whole human blood spiked with individual drugs were successfully analyzed without any pre-treatment. Irrespective of a laborious initial nano-DESI set-up, the combination of the kinetic method with nano-desorption electrospray has, for the first time, been demonstrated as a promising tool for chiral analysis of drugs in blood samples.

Capillary electrophoresis with laser-induced fluorescence and pre-column derivatization for the analysis of illicit drugs

In the current paper, we report the development of a new capillary electrophoresis method using pre-column derivatization and laser-induced fluorescence detection for the determination of ephedrine and amphetamine drugs. Our new method allows for the identification and quantification of six commonly used illicit drugs namely pseudoephedrine, ephedrine, amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine, and 3,4-methylenedioxymethylamphetamine, respectively, as well as propafenone (internal standard). Following derivatization with fluorescein isothiocyanate, a total of six amphetamine drugs and the internal standard could readily be separated using a fused-silica 75 micromID x 60 cm length (effective length: 50.2 cm) capillary column. The mobile phase consisted of buffer containing 20mM borate (pH 12, adjusted with sodium hydroxide). Samples were injected in pressure mode with the capillary being operated at 25kV/25 degrees C, and the detection of the derivatized compounds was sought using a laser-induced fluorescence (LIF) detector (lambda(ex)=488 nm and lambda(em)=520 nm), with a run-time of 20 min. The current method was validated with regard to precision (relative standard deviation, RSD), accuracy, sensitivity, linear range, limit of detection (LOD) and limit of quantification (LOQ). In human blood and urine samples, detection limits were 0.2 ngmL(-1), and the linear range of the calibration curves was 0.5-100 ngmL(-1). The intra-day and inter-day precisions were both less than 13.22%.

Combining poly (methacrylic acid-co-ethylene glycol dimethacrylate) monolith microextraction and on-line pre-concentration-capillary electrophoresis for analysis of ephedrine and pseudoephedrine in human plasma and urine

A method based on poly (methacrylic acid-co-ethylene glycol dimethacrylate) (MAA-EGDMA) monolith microextraction (PMME) and field-enhanced sample injection (FESI) pre-concentration technique was proposed for sensitive capillary electrophoresis-ultraviolet (CE-UV) analysis of ephedrine (E) and pseudoephedrine (PE) in human plasma and urine. The PMME device consisted of a regular plastic syringe (1 mL), a poly (MAA-EGDMA) monolithic capillary (2 cm x 530 microm I.D.) and a plastic pinhead connecting the former two components seamlessly. The extraction was achieved by driving the sample solution through the monolithic capillary tube using a syringe pump, for the desorption step, an aliquot of organic solvent, which normally provided an excellent medium to ensure direct compatibility for FESI in CE, was injected via the monolithic capillary and collected into a vial for subsequent analysis by CZE. The best separation was achieved using a buffer composed of 0.1M phosphate electrolyte (pH 2.5) and 10% acetonitrile (v/v). The combination of both pre-concentration procedures allowed the detection limits of the analytes down to 5.3 ng/mL and 8.0 ng/mL in human plasma and urine, respectively. Excellent method of reproducibility was found over a linear range 50-5000 ng/mL in plasma and urine sample. Plasma and urine samples from volunteers receiving pseudoephedrine have also been successfully analysed.

Development and evaluation of an efficient HPLC/MS/MS method for the simultaneous determination of pseudoephedrine and cetirizine in human plasma: Application to Phase-I pharmacokinetic study

A sensitive, simple and highly selective liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed and evaluated to determine simultaneously the concentrations of pseudoephedrine and cetirizine in human plasma. The chief benefit of the present method is the minimal sample preparation, as the procedure is only one-step protein precipitation. Two drugs were separated on a C(8) column and analyzed by LC/MS/MS using positive electrospray ionisation (ESI). The method had a chromatographic run time of 12.0 min and a linear calibration curve over the concentration range of 1.0-800 ng/ml for pseudoephedrine and 1.0-400 ng/ml for cetirizine, respectively. The lower limit of quantification of the two drugs was 1.0 ng/ml, respectively. The intra- and inter-batch precisions were less than 9.7%. The method described herein has been first used to reveal the pharmacokinetic characters in healthy Chinese volunteers treated with oral administration of different dosages of cetirizine dihydrochloride and controlled-released pseudoephedrine hydrochloride compound tablet, and approached the influence of a standard meal on the extent and rate of absorption of the combination tablet.

Detection and validated quantification of nine herbal phenalkylamines and methcathinone in human blood plasma by LC-MS/MS with electrospray ionization

The herbal stimulants Ephedra species, Catha edulis (khat), and Lophophora williamsii (peyote) have been abused for a long time. In recent years, the herbal drug market has grown owing to publicity on the Internet. Some ingredients of these plants are also ingredients of cold remedies. The aim of the presented study is to develop a multianalyte procedure for detection and validated quantification of the phenalkylamines ephedrine, pseudoephedrine, norephedrine, norpseudoephedrine, methylephedrine, methylpseudoephedrine, cathinone, mescaline, synephrine (oxedrine), and methcathinone in plasma. After mixed-mode solid-phase extraction of 1 ml of plasma, the analytes were separated using a strong cation exchange separation column and gradient elution. They were detected using a Q-Trap LC-ESI-MS/MS system (MRM mode). Calibration curves were used for quantification using norephedrine-d3, ephedrine-d3, and mescaline-d9 as internal standards. The method was validated according to international guidelines. The assay was selective for the tested compounds. It was linear from 10 to 1000 ng/ml for all analytes. The recoveries were generally higher than 70%. Accuracy ranged from - 0.8 to 20.0%, repeatability from 2.5 to 12.3%, and intermediate precision from 4.6 to 20.0%. The lower limit of quantification was 10 ng/ml for all analytes. No instability was observed after repeated freezing and thawing or in processed samples. The applicability of the assay was tested by analysis of authentic plasma samples after ingestion of different cold medications containing ephedrine or pseudoephedrine, and after ingestion of an aqueous extract of Herba Ephedra. After ingestion of the cold medications, only the corresponding single alkaloids were detected in human plasma, whereas after ingestion of the herb extract, all six ephedrines contained in the plant were detected. The presented LC-MS/MS assay was found applicable for sensitive detection and accurate and precise quantification of all studied analytes in plasma.

Quantification of trimetazidine in human plasma by liquid chromatography-electrospray ionization mass spectrometry and its application to a bioequivalence study

A rapid, sensitive and specific liquid chromatography-electrospray ionization mass spectrometric (LC-ESI-MS) method has been developed for the quantification of trimetazidine in human plasma. The analyte and the internal standard (pseudoephedrine) were extracted from plasma samples with n-hexane-dichloromethane (1:1, v/v) and analyzed on a C18 column. The chromatographic separation was achieved within 3.5 min using the mobile phase consisting of methanol/0.05% formic acid (80:20, v/v) and the flow rate was 1.0 ml/min. Ion signals m/z 181.0 and 148.0 were measured in the positive mode for trimetazidine and pseudoephedrine, respectively. The calibration curves were linear within the range of 0.4 to approximately 120 ng/ml. The lower limit of quantification (LLOQ) was 0.4 ng/ml with 0.5 ml plasma sample. The intra- and inter-day precisions were lower than 12% in terms of relative standard deviation (RSD). The inter-day relative error (RE) as determined from quality control samples (QCs), ranged from -1.4% to 3.3%. This validated method was successfully applied to the bioequivalent evaluation of two brands of trimetazidine tablets in 20 healthy volunteers.

Simultaneous determination of desloratadine and pseudoephedrine in human plasma using micro solid-phase extraction tips and aqueous normal-phase liquid chromatography/tandem mass spectrometry

Cation-exchange micro solid-phase extraction (SPE) tips and aqueous normal-phase (ANP) chromatography coupled with tandem mass spectrometry were explored for the rapid, selective and sensitive quantitation of desloratadine and pseudoephedrine in human plasma. A novel micro-SPE device was evaluated for analyte capacity, extraction efficiency and its ability to maximize recovery of an analyte of interest from bioanalytical matrices by successive replicates of linked extraction steps. Ion suppression using two different methods with micro-SPE tips was negligible when compared to protein precipitation. The use of ANP chromatography eliminated the need for sample reconstitution following extraction and was found to be highly selective. A reliable chromatography system was developed with a short duty cycle of 2 min/sample. The proposed bioanalytical method required 50 microL of plasma for the determination of desloratadine and pseudoephedrine at limits of quantitation of 0.1 and 1.25 ng/mL, respectively. The analytical method was validated in accordance with the FDA guidance on bioanalytical method validation; selectivity, linearity, reproducibility and accuracy were all acceptable.

Quantification of pseudoephedrine in human plasma by LC-MS/MS using mosapride as internal standard

A simple, sensitive and rapid high-performance liquid chromatography/positive ion electrospray tandem mass spectrometry (LC-MS/MS) method was developed and validated for the quantification of pseudoephedrine in human plasma using mosapride as internal standard. Following solid-phase extraction, the analytes were separated using an isocratic mobile phase on a reverse-phase column and analyzed by MS/MS in the multiple-reaction monitoring mode using the respective [M + H](+) ions, m/z 166/148 for pseuoephedrine and m/z 422/198 for the IS. The method exhibited a linear dynamic range of 2-1000 ng/mL pseudoephedrine in human plasma. The lower limit of quantification was 2 ng/mL with a relative standard deviation of less than 9% for pseudoephedrine. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. The total chromatographic run time of 2 min for each sample made it possible to analyze more than 400 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic, bioavailability or bioequivalence studies.

Ventricular tachycardia induced by abuse of ephedrine in a young healthy woman

INTRODUCTION

Ephedrine or ephedra herbal products have occasionally been used to enhance sports performance and energy or to aid weight loss. The most serious side effects are those on cardiovascular function, including acute myocardial infarction, severe hypertension, myocarditis and lethal cardiac arrhythmias.

CASE REPORT

A 19-year-old woman was taking ephedrine to enhance her sports performance. After 10 days of this medication she developed hemodynamically unstable ventricular tachycardia resistant to cardioversion and amiodarone treatment. She converted to sinus rhythm 60 hours later, presumably when the plasma ephedrine level had sufficiently decreased. In an electrophysiological study the ventricular tachycardia could be induced and successfully ablated. There were no recurrences during follow-up of more than a year. The use of ephedrine carries a risk of development of life-threatening arrhythmias.

DISCUSSION

Ephedrine alone cannot be considered as the ultimate cause of tachycardia in our patient; however, it is highly probable that ephedrine triggered the tachycardic attack. The proarrhythmic effect most likely occurred because of underlying idiopathic left ventricular tachycardia. Although the patient could have developed her first attack of ventricular tachycardia at any time in her life, it is highly improbable that the attack following the ephedrine abuse was purely coincidental.

CONCLUSION

Our experience with the reported patient shows that ephedrine alone, or in combination with substances that increase its effects on the cardiovascular system, may also trigger paroxysms of non-ischemic ventricular tachycardia. The use of ephedrine carries a risk of development of life-threatening arrhythmias and should be discouraged.

Sensitive bioassay for the simultaneous determination of pseudoephedrine and cetirizine in human plasma by liquid-chromatography–ion trap spectrometry

A liquid chromatography-ion trap mass spectrometry coupled with electrospray ionization (HPLC-ESI-ion trap mass spectrometry) method for simultaneous determination of cetirizine and pseudoephedrine in human plasma is presented. Chromatographic separation was performed on a Hypurity C18 column (Thermo Hypersil-Keystone 2.1 mm x 150 mm, 5 microm, USA), The mobile phase was composed of 65% methanol and 35% water (contained 0.1% formic acid, 10 mM ammonium formate), which was run with a flow-rate of 0.2 ml/min at 40 degrees C. Quantitation was achieved by monitoring the product ions at m/z 166-->m/z 148 (pseudoephedrine), m/z 389.9-->m/z 201.1 (cetirizine), m/z 264-->m/z 246 (tramadol, IS). The calibration curve of pseudoephedrine and cetirizine was established with standard solutions. The limit of detection for pseudoephedrine and cetirizine each was 5 ng/ml. This simplified analytical method is sensitive, specific and accurate enough for simultaneous determination of pseudoephedrine and cetirizine in human plasma and is successfully applied to the pharmacokinetic study of pseudoephedrine and cetirizine.

Centrifuge Microextraction Coupled with On-Line Back-Extraction Field-Amplified Sample Injection Method for the Determination of Trace Ephedrine Derivatives in the Urine and Serum

Although sample stacking has enjoyed some degree of success in electrophoretic separation techniques, there is still a major problem with complex matrix sample as it suffers tremendously from sample matrix effects. A novel method that combines two concentration techniques, centrifuge microextraction (CME) and on-line back-extraction field-amplified sample injection (OLBE-FASI), is used to determine trace ephedrine derivatives in urine and serum by capillary zone electrophoresis. The CME, integrating the sample cleanup and preconcentration into a single step, is a promising sample preparation method for biological samples. The CME technique provided 9-14-fold enrichment within 10 min. The OLBE-FASI eliminated the need to perform solvent exchange and provided a further concentration of the analytes. Using CME coupled with OLBE-FASI, over a 3800-fold increase in sensitivity could be obtained as compared with the normal hydrodynamic injection without sample stacking. For a 1-mL urine sample, the linear range was 5/10-200 ng/mL with the square of the correlation coefficients (r(2)) ranging from 0.9988 to 0.9994. Detection limits were from 0.15 to 0.25 ng/mL using a photodiode array UV detection at wavelength 192 nm. The possibility of this method to determine ephedrine derivatives in 20-muL serum samples was also demonstrated.

[Simultaneous determination of ephedrine and chlorpheniramine in human plasma by a highly sensitive liquid chromatography-tandem mass spectrometric method]

AIM

To develop and validate a liquid chromatography-tandem mass spectrometric (LC/MS/MS) method for the simultaneous quantification of ephedrine and chlorpheniramine in human plasma after oral administration of a compound preparation.

METHODS

The analytes and the internal standard, diphenhydramine, were isolated from plasma by protein precipitation with methanol, then chromatographied on a Zorbax SB-C18 column (150 mm x 4.6 mm ID) using a mobile phase consisted of methanol-water-formic acid (80: 20: 0.5, v/v), at a flow rate of 0.5 mL x min(-1). A tandem mass spectrometer equipped with electrospray ionization source was used as detector and was operated in the positive ion mode. Selected reaction monitoring (SRM) using the precursor to produce ion combinations of m/z 166-->115, m/z 275-->230 and m/z 256-->167 were used to quantify ephedrine, chlorpheniramine and the internal standard, respectively. Results The linear concentration ranges of the calibration curves for ephedrine and chlorpheniramine were 0.50 - 200 microg x L(-1) and 0.050 - 20.0 microg x L(-1), respectively. The lower limits of quantification were 0. 50 microg x L(-1) for ephedrine and 0.050 microg x L(-1) for chlorpheniramine, individually. The intra- and inter-day relative standard deviation (RSD) across three validation runs over the entire concentration range was less than 9.3% for both ephedrine and chlorpheniramine. The inter-day accuracy (RE) was within +/- 3.4% for the analytes. Each sample was chromatographied within 3.3 min. The method was successfully used in pharmacokinetics study of ephedrine and chlorpheniramine in human plasma after oral administration of a compound preparation containing 5 mg ephedrine hydrochloride, 1 mg chlorpheniramine maleate, 50 mg phenytoin, 12.5 mg theophylline, 12.5 mg theobromine and 7.5 mg caffeine. No interaction among the six components was observed on their pharmacokinetic parameters.

CONCLUSION

The method was proved to be highly sensitive, selective, and suitable for pharmacokinetics investigations of different compound preparations containing low dosage of both ephedrine and chlorpheniramine.

Simultaneous quantification of fexofenadine and pseudoephedrine in human plasma by liquid chromatography/tandem mass spectrometry with electrospray ionization: method development, validation and application to a clinical study

To support the pharmacokinetic and bioavailability study of a once-daily fexofenadine/pseudoephedrine combination, a high-performance liquid chromatography/positive ion electrospray tandem mass spectrometry (HPLC/ESI-MS/MS) method for the simultaneous quantification of fexofenadine and pseudoephedrine was developed and validated with 500 microL human plasma using mosapride as an internal standard (IS). Following solid-phase extraction, the analytes were separated using an isocratic mobile phase on a reversed-phase column and analyzed by MS/MS in the multiple reaction monitoring mode using the respective [M+H]+ ions, m/z 502/466 for fexofenadine, m/z 166/148 for pseuoephedrine and m/z 422/198 for the IS. The method exhibited linear dynamic ranges of 1-500 ng/mL and 2-1000 ng/mL for fexofenadine and pseudoephedrine, respectively, in human plasma. The lower limits of quantification were 1 and 2 ng/mL with a relative standard deviation of less than 10% for fexofenadine and pseudoephedrine, respectively. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. The total chromatographic run time was 2 min and more than 400 human plasma samples could be analyzed in one day by running the system overnight. The method is precise and sensitive enough for its intended purpose.

Development of a liquid chromatography/tandem mass spectrometry assay for the quantification of lisinopril in human plasma

A simple and sensitive liquid chromatography/tandem mass spectrometry method employing electrospray ionization, to quantify lisinopril in human plasma using pseudoephedrine hydrochloride as the internal standard (IS), has been developed and validated. A mixture of methanol and 0.1% formic acid in water (50:50, v/v) was used as the isocratic mobile phase. A simple liquid-liquid extraction procedure was used as sample preparation method. The method validation demonstrated the specificity, lower limit of quantification, accuracy, and precision of measurements. Selected reaction monitoring was specific for lisinopril and pseudoephedrine hydrochloride; no endogenous materials from blank plasma interfered with the analysis of lisinopril or the IS. The assay was linear over the concentration range 0.78-100 ng/mL. The correlation coefficients for the calibration curves ranged from 0.9984-0.9998. The intra- and inter-day precision, determined for quality control samples, were less than 4.18%. The method was employed in a pharmacokinetic study after oral administration of 10 mg lisinopril to 20 healthy volunteers.

Simultaneous determination of loratadine and pseudoephedrine sulfate in human plasma by liquid chromatography–electrospray mass spectrometry for pharmacokinetic studies

To support the pharmacokinetic and bioavailability study of an extended-release loratadine (LOR)/pseudoephedrine sulfate (PES) tablet, a high performance liquid chromatographic-electrospray ionisation-mass spectrometric method (LC-MS) was developed for the simultaneous determination of LOR and PES in human plasma. Diazepam (DP) and phenylpropanolamine (PPA) were used as internal standards for LOR and PES, respectively. Analytes were extracted from alkalized human plasma by liquid/liquid extraction using ethyl ether. Chromatographic separation was performed on an ODS column at flow rate of 0.2 ml/min. The total chromatographic run time was 10.5 min with the retention time of 7.1 min and 6.2 min for LOR and DP, respectively, and 2.2 min for both of PES and PPA. The LOQ was 10 pg/ml and 50 pg/ml for LOR and PES, respectively. The method is accurate and precise enough for its intended purpose.

Mechanistic pharmacokinetic modelling of ephedrine, norephedrine and caffeine in healthy subjects

AIM

The combination of ephedrine and caffeine has been used in herbal products for weight loss and athletic performance-enhancement, but the pharmacokinetic profiles of these compounds have not been well characterized. This study aimed to develop a mechanistic model describing ephedrine, norephedrine, and caffeine pharmacokinetics and their interactions in healthy subjects.

METHODS

The pharmacokinetic model was developed based on the simultaneous modelling using plasma samples gathered from two clinical trials. The treatments consisted of single-doses of pharmaceutical caffeine and ephedrine, given alone or together, and an herbal formulation containing both caffeine and ephedrine. We used a mixed-effect statistical model and the program NONMEM to take account of intersubject variability.

RESULTS

Three hundred and seventy-nine ephedrine, 352 norephedrine, 417 caffeine plasma concentrations and 40 ephedrine urine concentrations were obtained from 24 subjects. A one-compartment model with first-order absorption described the caffeine data. Caffeine clearance was 0.083 l min(-1) (CV 38%) and decreased to 0.038 l min(-1) in presence of oral contraceptive therapy, its volume of distribution was 38.6 l (CV 20%) and its absorption rate constant was 0.064 l min(-1) (CV 50%). A four-compartment model described the pharmocokinetics of ephedrine and norephedrine. Ephedrine was eliminated mostly renally, with a clearance of 0.34 l min(-1) (CV 11%), and a volume of distribution of 181 l (CV 19%). Nonlinearity in the conversion of ephedrine to norephedrine was observed. Different models showed that the simultaneous administration of caffeine, or the amount of caffeine in the absorption compartment, was associated with a slower rate of absorption of ephedrine. A 32% greater relative bioavailability of herbal compared with pharmaceutical ephedrine administration was observed.

CONCLUSIONS

We describe a mechanistic model for ephedrine, norephedrine and caffeine pharmacokinetics and their interactions. The relative bioavailability of ephedrine differed between the herbal supplement compared with the pharmaceutical formulation. Concomitant ingestion of caffeine slowed the absorption rate of ephedrine, which is mainly related to the amount of the former in the absorption compartment. A saturable process appears to be involved in the metabolism of ephedrine to norephedrine.

Simultaneous determination of methylephedrine and noscapine in human plasma by liquid chromatography–tandem mass spectrometry

A selective and sensitive method has been developed and validated for simultaneous quantification of methylephedrine and noscapine in human plasma. Analytes were extracted from human plasma samples by liquid-liquid extraction, separated on a Diamonsil C18 column and detected by tandem mass spectrometer with an atmospheric pressure chemical ionization (APCI) interface. Diphenhydramine was used as the internal standard (I.S.). The method was found to be precise and accurate within the linear range 0.1-100 ng/ml for each analyte. The intra- and inter-day relative standard deviations (R.S.D.s) were below 5.2% for methylephedrine and 6.7% for noscapine. The inter-day relative error (RE) as determined from quality control samples (QCs) was less than 3.0% for each analyte. The assay was successfully employed in a pharmacokinetic study after an oral administration of a multicomponent formulation containing 20 mg DL-methylephedrine hydrochloride, 16 mg noscapine, 300 mg paracetamol and 1mg of chlorpheniramine maleate.

[Dietary supplements--surprise pills?]

BACKGROUND

Sales of herbal dietary supplements have increased dramatically. A patient case drew our attention to the problem of incomplete declaration of content.

METHODS

Two dietary supplements which the manufacturers claim to be natural, extremely fat-burning and energizing were analysed, as were urine and serum samples from persons taking these supplements.

RESULTS

Surprisingly, the herbal dietary supplements contained drugs. Diazepam, clonazepam, ephedrine and metabolites were found when analyzing serum samples after intake of the dietary supplement Thermo-X 650, ephedrine and phenylpropanolamine after intake of the Purple Burn supplement.

INTERPRETATION

Use of herbal dietary supplement can have serious consequences, for instance through interactions with drug therapy. Consumers must be given sufficient product information for safe use.

Gas chromatography/mass spectrometry determination of amphetamine-related drugs and ephedrines in plasma, urine and hair samples after derivatization with 2,2,2-trichloroethyl chloroformate

A new analytical approach, based on derivatization with 2,2,2-trichloroethyl chloroformate and gas chromatography/mass spectrometry (GC/MS), was investigated for qualitative and quantitative analyses of a large range of amphetamine-related drugs and ephedrines in plasma, urine and hair samples. Sample preparation involved alkaline extraction of analytes from biological samples using Extrelut columns, after addition of the internal standard 3,4-methylenedioxypropylamphetamine (MDPA), and subsequent derivatization to produce 2,2,2-trichloroethylcarbamates. GC/MS analyses, in splitless mode using a slightly polar 30-m capillary column, were performed with quadrupole or ion trap instruments. MS acquisition modes were electron ionization (EI) in full-scan or selected ion monitoring (SIM) modes (quadrupole), and full-scan MS or MS/MS modes with chemical ionization (CI) conditions (ion trap). EI spectra of 2,2,2-trichloroethylcarbamates showed variably abundant molecular ions as well as abundant diagnostic fragment ions, both characterized by ion clusters reflecting the isotope distribution of three chlorine atoms in the derivatized molecules. CI spectra showed abundant protonated molecules. Quantitative studies using EI SIM conditions gave recoveries in the range 74-89%, linear response over ranges of 10-2000 ng/mL (plasma and urine) and 0.20-20 ng/mg (hair), with corresponding limits of detection in the ranges 2-5 ng/mL and 0.1-0.2 ng/mg. Potential applications (following full method validation) include clinical and forensic toxicology, as well as doping control.

Determination of ephedra alkaloid and caffeine concentrations in dietary supplements and biological fluids

Dietary supplements containing botanical forms of caffeine and ephedra alkaloids have been widely promoted and used in the U.S. for weight loss and athletic enhancement despite a lack of adequate research on the pharmacology of these botanical stimulants. In order to analyze dietary supplements and perform human pharmacokinetic studies, an analytical approach with good precision and accuracy was needed with sufficient sensitivity to detect very low levels of ephedra alkaloids. A liquid chromatography-atmospheric pressure chemical ionization (APCI) tandem mass spectrometry (LC-MS-MS) method was developed for quantitating the various ephedrine-group alkaloids found in dietary supplements that contain Ephedra species, and in plasma and urine of persons consuming these supplements. Using this method, low nanogram-per-milliliter concentrations of ephedrine, pseudoephedrine, norephedrine, norpseudoephedrine, methylephedrine, methylpseudoephedrine, and caffeine can be quantitated in a 12-min LC-MS-MS run.

Simultaneous determination of chlorpheniramine and pseudoephedrine in human plasma by liquid chromatography–tandem mass spectrometry

A sensitive and specific procedure for simultaneous quantitation of chlorpheniramine and pseudoephedrine in human plasma has been developed and validated. Analytes were extracted from plasma samples by liquid-liquid extraction, separated on a Diamonsil C18 column (250 x 4.6 mm i.d.) and detected by tandem mass spectrometry with an atmospheric pressure chemical ionization interface. Diphenhydramine was used as the internal standard. The method has a lower limit of quantitation of 0.2 and 2.0 ng/mL for chlorpheniramine and pseudoephedrine, respectively. The intra- and inter-day relative standard deviation, calculated from quality control (QC) samples were below 4.3% for chlorpheniramine and below 9.5% for pseudoephedrine. The inter-day relative error as determined from QC samples was within 4.7% for each analyte. The overall extraction recoveries of chlorpheniramine and pseudoephedrine were 77 and 61% on average, respectively. The method was successfully applied to pharmaockinetic study of chlorpheniramine and pseudoephedrine in volunteers receiving formulations containing 4 mg of chlorpheniramine maleate and 60 mg of pseudoephedrine hydrochloride.

[Simultaneous determination of pseudoephedrine and chlorpheniramine in human plasma by HPLC-UV detection method]

AIM

To establish a sensitive and specific method to simultaneous determination of pseudoephedrine and chlorpheniramine in human plasma.

METHODS

Pseudoephedrine and chlorpheniramine were extracted from alkaline plasma with t-butyl methyl ether as the base form, and were back-extracted into 1.5% hydrochloride solution. The two drugs were simultaneous determined by RP-HPLC with ultraviolet detection at 200 nm, using dextromethorphan as internal standard. A C18 column (250 mm x 46 mm ID) and a mobile phase containing acetonitrile-water-triethylamine (46:54:0.2, containing 10 mmol x L(-1) sodium dodecyl sulfate (SDS) and 60 mmol x L(-1) NaH2 PO4, adjusted pH to 2.6 with H3PO4) were used.

RESULTS

The limit of quantification was 10.0 and 0.5 microg x L(-1), the linear range was 1.5 - 0.01 mg x L(-1) and 75 - 0.5 microg x L(-1), for pseudoephedrine and chlorpheniramine, respectively. The within-day and between-day RSD were less than 12.4%, and the average recovery was between 97.3% - 109.4%.

CONCLUSION

The method was sensitive, specific, simple, and suitable for drug level monitoring in clinical pharmacokinetic study.

Determination of ephedra alkaloids in urine and plasma by HPLC-UV: collaborative study

Ten collaborating laboratories determined the ephedra alkaloid content (ephedrine, pseudoephedrine, norephedrine, norpseudoephedrine, methylephedrine, and methylpseudoephedrine) in 8 blind duplicates of human plasma and urine using high-performance liquid chromatography (HPLC) with UV detection. In addition to negative urine and plasma controls, urine samples were spiked with individual ephedra alkaloids ranging in concentration from about 1 to 5 microg/mL. Plasma samples were spiked with individual ephedra alkaloids ranging in concentration from about 100 to 400 ng/mL. Sample solutions were treated to solid-phase extraction using a strong-cation exchange column to help remove interferences. The HPLC analyses were performed on a polar-embedded phenyl column using UV detection at 210 nm. The ephedra alkaloids were not consistently detected in any of the spiked plasma samples. When ephedra alkaloids were detected in the plasma samples, reproducibility between blind replicate samples was very poor. Repeatability, reproducibility, and accuracy were also very poor for the spiked urine samples. On the basis of these results, the HPLC-UV method for the determination of ephedra alkaloids in human urine and plasma is not recommended for adoption as Official First Action.