Elimination of matrix effects in urine for determination of ethyl glucuronide by liquid chromatography-tandem mass spectrometry.

RATIONALE: Alcohol use disorder affects 4% to 5% of the world's population. Analysis methods are available for various biological fluids to detect this disorder. Determination of ethyl glucuronide in urine by the liquid chromatography-tandem mass spectrometry (LC/MS/MS) method is frequently used in forensic toxicology. These analyses are known to cause matrix effects. METHODS: The presented study describes the elimination of matrix effects for ethyl glucuronide. This study used two different LC/MS/MS systems containing orthogonal and z-spray ion sources. Ethyl glucuronide was analyzed in negative polarity in electrospray ionization. A different dilution method was chosen for each study. The methods were developed and validated according to the European Medicines Agency bioanalytical method validation parameters. RESULTS: The lower limit of quantitation of the developed methods was 0.025 µg/mL for ethyl glucuronide. The calibration curve of ethyl glucuronide was between 0.025 and 100 µg/mL with a correlation coefficient of >0.99 for the two methods. CONCLUSIONS: It was determined that the analyses using the z-spray ion source were more affected by the matrix effect. The two validated methods involve rapid analysis time and simple sample preparation. Also, the methods were applied to real patients' urine.

Determination of cefuroxime in breast milk by LC-MS/MS using SALLME technique.

The World Health Organization recommends that infants be exclusively breastfed for the first 6 months. Antibiotics are among the most commonly prescribed drugs for pregnant and lactating women. The vast majority of drugs pass into breast milk, which may create a risk for the infant. In cases where drug exposure may pose a risk, breastfeeding should be discontinued. Therefore, the mother's drug use should be decided by considering the most accurate and recent data. Cefuroxime is a second-generation cephalosporin antibiotic with a broad spectrum of activity against Gram-negative and -positive microorganisms. In this study, we aimed to develop the LC-MS/MS method using salt-assisted liquid-liquid micro-extraction (SALLME) for the determination of cefuroxime in breast milk. The method was validated according to the European Medicines Agency (EMA) guidelines. Cefuroxime and the internal standard cefixime were extracted from plasma by a SALLME technique. The results obtained from the entire validation study are at an acceptable level according to the EMA criteria. The calibration curve of cefuroxime was between 25 and 1000 ng/ml, with correlation coefficients of >0.99. The lower limit of quantitation was 25 ng/ml for cefuroxime. Furthermore, the developed method was applied for the determination of cefuroxime in real patient breast milk.

Development and Evaluation of Combined Effect Buccal Films for Treatment of Oral Candidiasis.

Buccal film formulations, including antifungal nystatin, anti-inflammatory agent hydrocortisone acetate, and local anesthetic lidocaine hydrochloride for pain relief, were developed. Bioadhesive films were fabricated with hydrophilic polymers, hydroxyethyl cellulose (HEC), and xanthan gum (XG) and dried in the incubator. Textural, swelling, and bioadhesive properties, physicochemical and in vitro release characteristics, and antifungal activities of bioadhesive films were evaluated.Bioadhesive films significantly extended nystatin release by prolonging retention time of the target area formulation while rapidly releasing hydrocortisone acetate and lidocaine HCl, reducing drug administration. The polymer type affected bioadhesion strength and erosion ratio, and XG formulations had more polymer suitability. Consequently, XT-O2 formulation that was prepared with xanthan gum and tween 80, was best for its highest antifungal film activity (20.00 ± 0.07 mm), released nystatin (44.296% ± 1.695), and lowest erosion matrix (36.719% ± 0.249). The selected formulation can be used for compatibility, stability and in vivo studies targeted oral candidiasis infections.

Determination of levetiracetam in human plasma by online heart-cutting liquid chromatography: Application to therapeutic drug monitoring.

Levetiracetam is an antiepileptic drug for the treatment of psychiatric patients. In this study, a selective, straightforward, and rapid online heart-cutting liquid chromatography method was developed for the therapeutic drug monitoring of levetiracetam. This method allows for the determination of levetiracetam in human plasma without complex sample preparation. The mobile phases consisted of 30 mM aq. orthophosphoric acid solution/methanol (70:30) at a flow rate of 1 mL/min for the first system and 10 mM aq. orthophosphoric acid solution/methanol (55:45) at a flow rate of 1 mL/min for the second system. The first separation was carried out on a GL Sciences Intersil ODS-3 column (4.6 mm × 150 mm, 3 µm) and the second separation was carried out on a Restek Ultra PFPP column (4.6 mm × 150 mm, 5 µm). The detection was carried out at 205 nm for both systems. The method was validated for selectivity and linearity, which were in the 6-60 µg/mL range. Intra- and interassay accuracies were <112.6%, and the intra- and interassay precisions were <6.4% for all quality control samples. The lower limit of quantitation was 6 µg/mL. The developed method was successfully applied for therapeutic drug monitoring of plasma samples from patients.

Determination of acamprosate in human plasma by UPLC-MS/MS: Application to therapeutic drug monitoring.

Acamprosate is a medication used to treat alcohol dependence. Therapeutic drug monitoring is important in drugs for the treatment of substance-related disorders. Therefore, in this study, a new selective, very simple and rapid ultra-performance liquid chromatography-tandem mass spectrometer method was developed for the therapeutic drug monitoring of acamprosate. The developed method allows the determination of acamprosate in human plasma. The method was validated in terms of selectivity and linearity, which was in the range of 100-1,200 ng/ml for acamprosate. Intra-assay and inter-assay accuracy and precision were within the acceptable limits of the Eueopean Medicines Agency guideline. The lower limit of quantitation was 100 ng/ml for acamprosate. The developed method was successfully applied for therapeutic drug monitoring in patient plasma samples.

Preparation and in-vivo evaluation of dimenhydrinate buccal mucoadhesive films with enhanced bioavailability.

Dimenhydrinate (DMH)-loaded buccal bioadhesive films for the prevention and treatment of motion sickness were prepared and optimized. This study examines the rate of drug release from the films for prolonged periods of time to reduce or limit the frequency of DMH administration. Based on preliminary studies using various polymers and concentrations, hydroxyethylcellulose (2.5, 3.0, and 3.2%), and xanthan gum (2.8%) were chosen as matrix polymers. The films were analyzed with respect to their mechanical, physicochemical, bioadhesive, swelling, and in-vitro release properties. In in-vivo pharmacokinetic studies, xanthan gum-based DMH buccal film was associated with significantly increased DMH plasma levels between 1 h and 5 h after DMH dosing when compared with an oral drug solution. The area under the curve AUC0-7 h value of the mucoadhesive buccal film was two-fold higher than the oral DMH solution. Histological analysis revealed that DMH films cause mild morphological and inflammatory changes in rabbit buccal mucosa. The DMH buccal film is effective for approximately 7 h, thus representing an option for single-dose antiemetic therapy. This dosage regimen could be particularly beneficial for chain travelers who travel for long periods of time.

A very simple high-performance liquid chromatographic method with fluorescence detection for the determination of gemifloxacin in human breast milk.

A high-performance liquid chromatographic method with fluorescence detection was developed and validated for the determination of gemifloxacin in human breast milk. The proposed method allows the determination of gemifloxacin in breast milk samples without complex sample preparation. The samples were mixed with a mobile phase and filtered with a 0.45 µm polytetrafluoroethylene filter before analysis. Chromatographic separation was carried out on a C18 column (150 × 4.6 mm, 5 µm I.D.) using methanol:50 mM ortho-phosphoric acid solution (40:60) as the mobile phase with a 1.0 mL/min flow rate. Quantitation was performed using fluorescence detection with an excitation wavelength at 272 nm and an emission wavelength at 395 nm. The linear range was found to be 0.1-2.5 µg/mL. The method was applied successfully for the determination of gemifloxacin in breast milk obtained from a breastfeeding mother after oral administration of a single tablet that included 320 mg gemifloxacin per gemifloxacin tablet.

Development of sensitive spectrofluorimetric and spectrophotometric methods for the determination of duloxetine in capsule and spiked human plasma.

A new, sensitive and selective spectrofluorimetric method has been developed for the determination of duloxetine (DLX) in capsule and spiked human plasma. DLX, as a secondary amine compound, reacts with 7-chloro-4-nitrobenzofurazon (NBD-Cl), a highly sensitive fluorogenic and chromogenic reagent used in many investigations. The method is based on the reaction between the drug and NBD-Cl in borate buffer at pH 8.5 to yield a highly fluorescent derivative that is measured at 523 nm after excitation at 478 nm. The fluorescence intensity was directly proportional to the concentration over the range 50-250 ng/mL. The reaction product was also measured spectrophotometrically. The relation between the absorbance at 478 nm and the concentration is rectilinear over the range 1.0-12.0 µg/mL. The methods were successfully applied for the determination of this drug in pharmaceutical dosage form. The spectrofluorimetric method was also successfully applied to the determination of duloxetine in spiked human plasma. The suggested procedures could be used for the determination of DLX in pure form, capsules and human plasma being sensitive, simple and selective.

A novel method for the therapeutic drug monitoring of biperiden in plasma by GC-MS using salt-assisted liquid-liquid microextraction.

Biperiden is an anticholinergic agent with central effects. It is used in Parkinson's syndromes and in the treatment of extrapyramidal symptoms that occur with the use of various agents (neuroleptics, antipsychotics). It causes anticholinergic syndrome in high doses. For this reason, therapeutic drug monitoring of biperiden is important. This study, it was aimed to develop a validated GC-MS method for the therapeutic monitoring of biperiden in human plasma. Biperiden and internal standard biperiden-d5 were extracted from plasma using the salt-assisted liquid-liquid extraction method. The method was validated according to the European Medicines Agency (EMA), Bioanalytical method validation guidelines. The lower limit of quantification of the developed method was chosen as 0.5 ng/mL. The calibration curve of biperiden for the method was validated between 0.5 and 15 ng/mL, showing correlation coefficients >0.99. In addition, the developed method was used for the therapeutic drug monitoring of biperiden in real patient plasma.

A new method for the therapeutic drug monitoring of chlorpromazine in plasma by gas chromatography-mass spectrometry using dispersive liquid-liquid microextraction.

Background: Chlorpromazine is the first antipsychotic drug developed and is included in the list of 'essential drugs' prepared by the WHO. Therapeutic drug monitoring is an important point for psychotropic drugs because of significant genetic variability in their metabolism and poor compliance of the patients with treatment. Method: We developed a novel GC-MS method using dispersive liquid-liquid microextraction for the therapeutic monitoring of chlorpromazine. Results: The method was validated according to the European Medicines Agency guidelines. The developed method's lower limit of quantification was set as 30 ng/ml. The calibration curve of chlorpromazine was validated between 30 and 600 ng/ml, with correlation coefficients of more than 0.99. Conclusion: The developed method was applied to real human patient plasma.

Determination of Enzymatic Hydrolysis Efficiency in Detection of Cannabis Use by UPLC-MS-MS.

Cannabis is still the most widely used illegal plant in the world. However, cannabis use is prohibited in many countries. After cannabis use, Δ9-tetrahydrocannabinol is metabolized in the liver to 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THC-COOH) and most undergo glucuronidation. THC-COOH and THC-COOH glucuronide are excreted in the urine. The total concentration of THC-COOH in the urine sample is measured to determine cannabis use. The total concentration is determined after enzymatic or alkaline hydrolysis. In this study, comparing enzymatic hydrolysis efficiency is presented comprehensively together with the method developed for the determination of total THC-COOH in the urine. Also, the method was validated according to the European Medicines Agency Guidelines on bioanalytical method validation. The method has rapid hydrolysis time (20 min), rapid analysis time (5 min) and simple sample preparation. The lower limit of quantitation of the developed method was 1 ng/mL for THC-COOH. The calibration curve of THC-COOH was between 1 and 2,000 ng/mL with a correlation coefficient >0.99. Also, the method was applied to real patient's urine. We think that the results will provide a new perspective on enzymatic hydrolysis optimization studies.

Pharmacokinetic study of clarithromycin in human breast milk by UPLC-MS/MS.

This study aimed to develop a validated UPLC-MS/MS method for pharmacokinetic analysis of clarithromycin in human breast milk. For sample preparation, proteins precipitated with methanol and azithromycin were used as internal standards. Clarithromycin and azithromycin detection was achieved using electrospray ionization in positive mode. The chromatographic separation time was 5 min. The lower limit of quantification was 50 ng/mL. The calibration curve of clarithromycin was 50-4000 ng/mL, with a correlation coefficient> 0.99. The method was successfully applied to determine clarithromycin levels in breast milk obtained from a lactating mother after oral administration of a single tablet containing 500 mg of clarithromycin. The maximum human breast milk concentration (Cmax) was 3660 ng/mL, the time to reach the maximum concentration (tmax) was 2.5 h, and the area under curve (AUC0-24) was 18450 ng h/mL. The present study provides a novel UPLC-MS/MS method for pharmacokinetic analysis of clarithromycin in breast milk.

A new HPLC method with fluorescence detection for the determination of memantine in human plasma.

A sensitive, selective, simple and fast HPLC method based on the formation of derivative with fluorescamine was developed for the determination of memantine (ME) in human plasma. Separation was achieved on a CN column (200 mm×4.6 mm) using acetonitrile-10 mM orthophosphoric acid containing 1 mL/L triethylamine (45:55, v/v) at a flow rate of 1 mL/min. Emission and excitation wavelengths were 480 and 380 nm, respectively. Amantadine was used as an internal standard. Calibration graphs were rectilinear over the range of 1.0-100.0 ng/mL. Limit of detection and limit of quantification were found to be 0.3 and 1.0 ng/mL, respectively. Intra-day and inter-day relative standard deviation values were found to be <2.03%. Average recovery was also found to be around 94%. Proposed method was applied for the pharmacokinetic study in a healthy volunteer after a single oral administration of 20 mg of ME.

Determination of levofloxacin by HPLC with fluorescence detection in human breast milk.

Aim: A new HPLC method with fluorescence detection has been developed and validated for the determination of levofloxacin, one of the fluoroquinolone class antibiotics, in breast milk. Materials & methods: Chromatographic separation was carried out on a reversed phase C18 column with acetonitrile and 10 mM o-phosphoric acid (25:75, v/v) mobile phase composition. Moxifloxacin was used as internal standard and the peaks were detected by fluorescence detection. Results & conclusion: Calibration graph was found linearly within the range of 2.5-500 ng/ml. Limit of detection and limit of quantification were found to be 0.63 and 2.11 ng/ml, respectively. Mean absolute recovery was 96.18%. The developed method has been successfully applied to the determination of levofloxacin in human breast milk taken from two healthy volunteers.

A High-Performance Liquid Chromatographic Method for the Determination of Meropenem in Serum.

In this study, a new, sensitive and selective high-performance liquid chromatographic method was developed for the determination of meropenem (MEM) in human serum. In the developed method, C18 column (3.9 × 150 mm, 5 µm) was selected as stationary phase at 30°C, and methanol: acetic acid solution mixture was used as mobile phase with gradient program. Chromatographic separation was carried out at a flow rate of 1 mL/min, and detection was performed at 300 nm with diode array detector. Doripenem was selected as an internal standard, and the analytes were extracted from serum using protein precipitation method with ortho-phosphoric acid: methanol. Detection wavelength was selected as 300 nm. The developed method was validated according to International Council for Harmonisation (ICH) guidelines. The calibration curve was linear over a concentration range of 4-240 µg/mL with correlation coefficient of 0.9985. The limit of detection and limit of quantification values were found as 0.057 and 0.192 µg/mL, respectively. The validated method was successfully applied for the determination of MEM in human serum samples collected from patient volunteers at different time intervals, and therapeutic drug monitoring of MEM has been investigated.

Determination of pethidine of abuse and relevant metabolite norpethidine in urine by ultra-performance liquid chromatography-tandem mass spectrometry.

Pethidine is an opiate agonist used orally and parenterally. Pethidine-containing drugs abuse is frequently encountered on health workers and patients. The analysis methods used to determine the abuse of pethidine are important for forensic toxicology. Pethidine is metabolized to norpethidine by the liver. Therefore, the determination of pethidine and norpethidine in urine is one of the methods to determine the abuse of pethidine. In this study, we have developed a precise, simple and rapid ultra-performance liquid chromatography-tandem mass spectrometer method for the determination of pethidine and norpethidine simultaneously. The developed method was validated in terms of selectivity and linearity which was in the range of 9-1800 ng/mL for both pethidine and norpethidine. The intra-assay and inter-assay accuracy and precision were found within acceptable limits of the EMA guideline. Lower limits of quantitation were 9 ng/mL for both pethidine and norpethidine. The developed method was successfully applied for the determination of both analytes in the real samples.

Determination of linezolid in human breast milk by high-performance liquid chromatography with ultraviolet detection.

A rapid and simple HPLC method was developed for the determination of linezolid (LNZ) in human breast milk after a simple protein precipitation with methanol. The chromatographic separation was achieved on a C18 column (5 microm, 250 x 4.6 mm id) using a mobile phase of acetonitrile-10 mM acetic acid (25:75, v/v) at a flow rate of 1 mL/min. The LNZ peak was measured by photodiode array detection at 250 nm. The calibration graph was linear over the range of 0.5-20.0 microg/mL. The limits of detection and quantitation were found to be 0.1 and 0.5 microg/mL, respectively. The precision of the assay and the recovery of LNZ from breast milk at three different concentrations were assessed. The intraday and interday RSD values were found to be < 5%. The mean absolute recovery was 85.33%. The developed method was successfully applied to the determination of LNZ in breast milk obtained from the breastfeeding mother after oral administration of LNZ.

Spectrophotometric and spectrofluorimetric methods for the determination of pregabalin in bulk and pharmaceutical preparation.

Two new, sensitive and selective spectrofluorimetric and spectrophotometric methods have been developed for the determination of the gamma-amino-n-butyric acid derivative pregabalin (PGB) in bulk drug and capsule. Pregabalin, as a primary amine compound, reacts with 7-chloro-4-nitrobenzofurazon (NBD-Cl) which is a highly sensitive fluorogenic and chromogenic reagent used in many investigations. According to this fact, spectrophotometric and spectrofluorimetric methods for the determination of pregabalin in capsules were developed for the first time. The relation between the absorbance at 460 nm and the concentration is rectilinear over the range 0.5-7.0 microg mL(-1). The reaction product was also measured spectrofluorimetrically at 558 nm after excitation at 460 nm. The fluorescence intensity was directly proportional to the concentration over the range 40-400 ng mL(-1). The method was applied successfully to the determination of this drug in pharmaceutical dosage form. The mean recovery for the commercial capsules was 99.93% and 99.96% for spectrophotometric and spectrofluorimetric study, respectively. The suggested procedures could be used for the determination of PGB in pure and capsules being sensitive, simple and selective.

Determination of gabapentin in human plasma and urine by high-performance liquid chromatography with UV-vis detection.

A simple and reliable high-performance liquid chromatographic (HPLC) method with UV-vis detection has been developed and validated for the determination of gabapentin (GBP) in human plasma and urine. The clean up of the sample was carried out by solid-phase extraction with C18-cartridge. After the clean up procedure, the samples were pre-column derivatizated with 1,2-naphthoquinone-4-sulphonic acid sodium salt (NQS). A chromatographic separation was achieved on a C18 column with a mobile phase consisting of acetonitrile and 10mM orthophosphoric acid (pH 2.5) with isocratic elution (35:65). Baclofen was used as an internal standard (I.S.). The method developed for GBP was linear over the concentration range of 0.05-5.0 microg/ml and 0.1-10.0 microg/ml for plasma and urine, respectively. The method is precise (relative standard deviation, R.S.D. <4.05%) and accurate (relative mean error, RME <0.15%); mean absolute recoveries were 72.21% for plasma and 72.73% for urine.

An HPLC method for the determination of lisinopril in human plasma and urine with fluorescence detection.

A selective, sensitive and precise HPLC method with fluorimetric detection has been developed for the assay of lisinopril in human plasma and urine. The clean up of the sample was carried out by solid-phase extraction, firstly with C18-cartridge and secondly with a silica-cartridge. After a pre-column derivatization with fluorescamine, the reaction mixture was chromatographed on C18-column with gradient elution, using methanol and 0.02 M phosphate buffer (pH=3.2). The fluorescamine-lisinopril derivative was detected fluorimetrically by monitoring the emission at 477 nm, with excitation at 383 nm. Linear quantitative response curve was generated over a concentration range of 5-200 ng/ml and 25-1000 ng/ml for plasma and urine samples, respectively. The mean recovery of lisinopril from plasma and urine was 63.41 and 74.08%, respectively. Intra-day and inter-day R.S.D. and R.M.E. values at three different concentrations were assessed. The method was applied for pharmacokinetic study in a healthy volunteer after a single oral dose of 20 mg of the drug.