A simple and robust HPLC method for the determination of paroxetine in human plasma

Determination of paroxetine in blood and urine using micellar liquid chromatography with electrochemical detection

Paroxetine is a potent selective serotonin reuptake inhibitor used for the treatment of depression and related mood disorders. A micellar liquid chromatographic method was developed for the determination of paroxetine in serum and urine. Detection of paroxetine was carried out using a C18 column and a mobile phase of 0.15 M sodium dodecyl sulfate, 6% 1-pentanol at pH 3 (buffer salt 0.01 M NaH2PO4) running under isocratic mode at 1.0 mL/min and electrochemical detection at 0.8 V. The analyte was eluted without interferences in <15 min. The proposed methodology was validated under the guidelines of the International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use in matrix in terms of specificity, linearity (r(2) > 0.9999; 0.5-5 μg/mL range), accuracy (88-97.5%, recovery), repeatability (RSD < 0.54%), intermediate precision (RSD < 0.54%), limit of detection and quantification (0.001 and 0.005 μg/mL, respectively) and robustness (RSD < 3.63%). Developed method was successfully applied to real blood and urine samples as well as in spiked serum and urine samples. The developed method was specific, rapid, precise, reliable, accurate, inexpensive and then suitable for routine analysis of paroxetine in monitorized samples.

Paroxetine hydrochloride

Paroxetine hydrochloride (3S-trans)-3-[(1,3-benzodioxol-5-yloxy)methyl]-4-(4-fluorophenyl)-piperidine hydrochloride (or (-)-(3S,4R)-(4-(p-fluorophenyl)-3-[[3,4-(methylenedioxy)-phenoxy]methyl]piperidine hydrochloride), a phenylpiperidine derivative, is a selective serotonin reuptake inhibitor. Paroxetine is indicated for the treatment of depression, generalized anxiety disorder, obsessive-compulsive disorder, panic disorder, posttraumatic stress disorder, and social anxiety disorder. The physicochemical properties, spectroscopic data (1D and 2D NMR, UV, FT-IR, MS, PXRD), stability, methods of preparation and chromatographic methods of analysis of pharmaceutical, and biological samples of paroxetine are documented in this review. Pharmacokinetics, metabolism, and pharmacological effects are also discussed.

Modern bioanalytical methods for the rapid detection of antidepressants: SNRIs and SSRIs in human biological samples

Serotonin–norepinephrine-reuptake inhibitors (SNRIs) and selective serotonin-reuptake inhibitors (SSRIs) belong to a new generation of antidepressants used in the treatment of depression and other mood disorders. SSRIs act as reuptake inhibitors primarily via the inhibition of the neuronal reuptake of serotonin (5-HT) in the CNS. SNRIs have additional inhibitory activity at noradrenaline-reuptake sites. Different analytical methods for the routine monitoring and toxicological screening of SNRIs and SSRIs have been developed. Rapid quantification is a necessity for clinical use, allowing the possibility of diagnostics. This review focuses on recent advances of the methods that concern the determination of SSRIs and SNRIs in human biological samples. Sample preparation methodologies are discussed, because sample pretreatment is the most limiting and crucial step in analysis of biological matrices. Furthermore, information concerning the mechanism of action, side effects and toxicity are also given.

Determination of the antidepressant paroxetine and its three main metabolites in human plasma by liquid chromatography with fluorescence detection

A high-performance liquid chromatographic method has been developed for the determination in human plasma of the specific serotonin reuptake inhibitor (SSRI) antidepressant paroxetine and its three main metabolites (M1, M2, M3). Fluorescence detection was used, exciting at lambda = 294 nm and monitoring emission at lambda = 330 nm for paroxetine (lambda(exc) = 280 nm, lambda(em) = 330 nm for M1 and M2; lambda(exc) = 268 nm, lambda(em) = 290 nm for M3). Separation was obtained on a reversed-phase C18 column using a mobile phase composed of 66.7% aqueous phosphate at pH 2.5 and 33.3% acetonitrile. Imipramine (lambda(exc) = 252 nm, lambda(em) = 390 nm) was used as the internal standard. A careful pre-treatment of plasma samples was developed, using solid-phase extraction with C8 cartridges (50 mg, 1 mL). The calibration curves were linear over a working range of 2.5-100 ng mL(-1) for paroxetine and of 5-100 ng mL(-1) for all metabolites. The limit of detection (LOD) was 1.2 ng mL(-1) for PRX and 2.0 ng mL(-1) for the metabolites. The method was applied with success to plasma samples from depressed patients undergoing treatment with paroxetine. Hence, the method seems to be suitable for the therapeutic drug monitoring of paroxetine and its main metabolites in depressed patients' plasma.

Determination of Paroxetine in Human Plasma by High-Performance Liquid Chromatography Using 7,7,8,8-Tetracyanoquinodimethane as the Derivatization Reagent

A selective and sensitive reversed-phase HPLC method was developed for the determination of the antidepressant paroxetine in plasma. The method is based on the purple chromogen formed by a displacement reaction of paroxetine with 7,7,8,8-tetracyanoquinodimethane (TCNQ) in acetonitrile at 80 degrees C for 20 minutes. For the assay, the drug was extracted from 1 mL of plasma with chloroform and, after sample alkalinization, derivatized with TCNQ; then the reaction mixture was directly injected into a C18 column. Desipramine was used as internal standard. The mobile phase was acetonitrile-water (70:30) at a flow-rate of 1.0 mL/min, and the derivatives were eluted at 13.1 and 15.5 minutes for paroxetine and desipramine, respectively, and detected at 567 nm. Calibration curve was found linear over the range of 20-400 ng/mL, and the detection limit was 2 ng/mL at a signal-to-noise ratio of 3/1. Recoveries determined for 3 concentrations range between 81.3% and 88.1%. Intraday and interday relative standard deviation values were found to be within 3.8%-13.5% and 8.2%-14.6%, respectively. With this developed method, a pharmacokinetic study was performed for paroxetine.

Quantitative determination of paroxetine and its 4-hydroxy-3-methoxy metabolite in plasma by high-performance liquid chromatography/electrospray ion trap mass spectrometry: application to pharmacokinetic studies

A high-performance liquid chromatography (HPLC) method with tandem mass spectrometric detection is described for the determination of paroxetine, an antidepressant drug, and its metabolite (3S,4R)-4-(4-fluorophenyl)-3-(4-hydroxy-3-methoxyphenoxymethyl)piperidine (HM paroxetine) in human plasma. Plasma samples were hydrolysed with hydrochloric acid and then analytes were extracted with ethyl acetate at alkaline pH. Extracts were analysed by HPLC coupled to an atmospheric pressure ionisation-electrospray (ESI) interface and an ion trap mass spectrometer. Chromatography was performed on a reversed-phase column using acetonitrile/0.02% formic acid (66:34, v/v) as a mobile phase. The mass spectrometer was operated in the multiple reaction monitoring mode. The method was validated over concentration ranges of 0.75-100 microg/L and 5-100 microg/L for paroxetine and HM paroxetine, respectively. Mean recoveries of 77% for paroxetine and 76% for HM paroxetine were found, with precision always better than 15%. The limits of detection and quantification were 0.20 and 0.70 microg/L for paroxetine, and 0.70 and 2.20 microg/L for its metabolite. The method was applied to the analysis of plasma samples obtained from nine healthy male volunteers administered with a single oral dose of 20 mg paroxetine. After the 20-mg dose, the mean peak plasma concentration was 8.60 microg/L for paroxetine and 92.40 microg/L for HM paroxetine showing a tenfold ratio between the metabolite and the parent drug along the entire time-concentration curve.

High-performance liquid chromatography-mass spectrometry method for the determination of paroxetine in human plasma

A rapid and specific liquid chromatographic mass spectrometric (LC-MS-MS) method has been developed for the determination of paroxetine in human plasma. The procedure involves a liquid-liquid extraction of paroxetine and fluoxetine (internal standard) with cyclohexane-ethyl acetate. The standard curve was linear over a working range of 0.2-50 ng/ml. The lower limit of quantitation was 0.2 ng/ml. No endogenous compounds were found to interfere with the analysis. The absolute recovery was 70.8% for paroxetine and 84.1% for the internal standard. The accuracy of inter-assay and intra-assay accuracy was in the ranges -4.8 to -0.5% and -3.4 to 4.8%, respectively. This method proved to be suitable for bioequivalence studies by being simple, selective and reproducible.

Improved sample preparation for the quantitative analysis of paroxetine in human plasma by stable isotope dilution negative ion chemical ionisation gas chromatography-mass spectrometry

An improved sample work-up and derivatisation procedure for the quantitative determination of paroxetine in human plasma by gas chromatography-negative ion chemical ionisation mass spectrometry is presented. Solvent extraction from plasma samples at alkaline pH was combined with derivatisation to the pentafluorobenzyl carbamate derivative in one step and subsequently analysed without any further purification. Thus, lengthy and time-consuming solvent evaporation steps are avoided to assure high-throughput analysis. Complete validation data are presented. The method is rugged, rapid and robust and has been applied to the batch analysis of paroxetine during pharmacokinetic profiling of the drug.

High-performance liquid chromatographic method to screen and quantitate seven selective serotonin reuptake inhibitors in human serum

A high-performance liquid chromatographic screening method (HPLC) is described for the determination of seven selective serotonin reuptake inhibitors (SSRIs) (fluvoxamine, milnacipran, paroxetine, sertraline, fluoxetine, citalopram, venlafaxine) and for three pharmacologically active N-demethylated metabolites (desmethylcitalopram, didesmethylcitalopram and norfluoxetine). A tricyclic antidepressant, clomipramine, was used as an internal standard. The method consists of liquid extraction of serum after alcalinisation at pH 9.50, followed by chromatography on a Beckman C18 reversed-phase column. Compounds were detected at 200.4 nm. The standard curves were linear over a working range of 50-1,000 ng/ml for fluvoxamine, 15-1,000 ng/ml for fluoxetine, 25-500 ng/ml for norfluoxetine, 50-500 ng/ml for sertraline, 20-500 ng/ml for paroxetine, 25-550 ng/ml for citalopram, 25-750 ng/ml for desmethylcitalopram, 25-800 ng/ml for didesmethylcitalopram, 25-650 ng/ml for milnacipran, and 25-500 ng/ml for venlafaxine. The quantitation limits of the method were 15 ng/ml for fluoxetine, 20 ng/ml for paroxetine, 25 ng/ml for venlafaxine, norfluoxetine and citalopram, and its metabolites, 40 ng/ml for sertraline and 50 ng/ml for fluvoxamine. No interferences were noted with this sensitive and specific method which can be used for therapeutic drug monitoring.

Stable isotope dilution negative ion chemical ionization gas chromatography-mass spectrometry for the quantitative analysis of paroxetine in human plasma

A sensitive and specific method for the quantitative determination of paroxetine in human plasma is presented. After solvent extraction from plasma with hexane/ethyl acetate (1 : 1) at alkaline pH and derivatization to the pentafluorobenzyl carbamate derivative, paroxetine was measured by gas chromatography-negative ion chemical ionization mass spectrometry. The carboxylate anion at m/z 372 was obtained at high relative abundance. [2H6]-labeled paroxetine was used as an internal standard and its rapid and facile preparation from the unlabeled compound is described. Calibration graphs were linear within a range of 0.094-12.000 ng x ml(-1) using 1 ml of plasma and 0.469-60 ng x ml(-1) using 200 microl of plasma. Intra-day precision was 1.47% (0.375 ng x ml(-1)), 3.16% (3 ng x ml(-1)) and 1.37% (9 ng x ml(-1)) for the low-level method, and 3.37% (1.875 ng x ml(-1)), 2.72% (15 ng x ml(-1)) and 2.22% (45 ng x ml(-1)) for the high-level method. Inter-day precision was 1.65% (0.375 ng x ml(-1)), 2.13% (3 ng x ml(-1)) and 1.66% (9 ng x ml(-1)) for the low-level method, and 1.10% (1.875 ng x ml(-1)), 1.56% (15 ng x ml(-1)) and 1.90% (45 ng x ml(-1)) for the high-level method. At the limit of quantification (0.094 ng x ml(-1)), intra-day precision was 4.30% (low-level method) and 2.56% (high-level method), and inter-day precision was 3.23% (low-level method) and 3.00% (high-level method). The method is rugged, rapid and robust and has been applied to the batch analysis of paroxetine during pharmacokinetic profiling of the drug.

Determination of paroxetine levels in human plasma using gas chromatography with electron-capture detection

A simple, rapid and sensitive procedure using gas chromatography with electron-capture detection to measure paroxetine levels in human plasma has been developed. The analyte was extracted from plasma with ethyl acetate after basification of the plasma and then derivatized with heptafluorobutyric anhydride before gas chromatographic separation. The calibration curves were linear, with typical r2 values >0.99. The assay was highly reproducible and gave peaks with excellent chromatographic properties.

Method development and validation for the HPLC assay (potency and related substances) for 20 mg paroxetine tablets

A reversed phase high performance liquid chromatographic (HPLC) method was developed and validated for use as a stability indicating assay (potency and related substances) of paroxetine in paroxetine hydrochloride 20 mg tablets. Assay samples were extracted at a paroxetine concentration of 0.4 mg ml(-1) utilizing mobile phase as the extraction solvent. The chromatographic conditions employed a C18 column (Inertsil, 5 microm, 15 cm x 4.6 mm), isocratic elution with 10 mM 1-decane sulfonic acid sodium salt containing 10 mM sodium phosphate monobasic (pH 3.0)-ACN (60:40, v/v) and ultraviolet (UV) detection at 235 nm.

Determination of paroxetine in plasma by high-performance liquid chromatography for bioequivalence studies

A high-performance liquid chromatographic method is described for the determination of paroxetine in human plasma. Dibucaine was used as the internal standard. Paroxetine was isolated by solid phase extraction using a Bond-Elut C18 extraction column. Separation was obtained using a reversed-phase column under isocratic conditions with fluorescence detection. The sample volume was 500 microliters of plasma. The intra- and inter-assay accuracy and precision, determined as relative error and relative standard deviation, respectively, were less than 10%. The lower limit of quantitation, based on standards with acceptable relative error and relative standard deviation, was 10 ng ml-1. No endogenous compounds were found to interfere. The linearity was assessed in the range 5-100 ng ml-1. Stability of paroxetine during processing (autosampler) and in plasma was checked. This method proved suitable for bioequivalence studies following multiple doses in healthy volunteers.

Validated chiral high-performance liquid chromatographic method for the determination of trans-(-)-paroxetine and its enantiomer in bulk and pharmaceutical formulations

A stereospecific high-performance liquid chromatography method for the determination of trans-(-)-paroxetine and its enantiomer in bulk raw material and pharmaceutical formulations was developed and validated. The enantiomeric separation was achieved, without any derivatization, on a carbamate derivative-based column (Chiralpak AD). The effect of the organic modifiers, 2-propanol and ethanol, in the mobile phases was optimised to obtain enantiomeric separation. Limits of detection and quantitation of 2 and 6 ng, respectively, were obtained for both of the enantiomers. The linearity was established in the range of 5-41 microg for trans-(-)-paroxetine and in the range of 10-160 ng for trans-(+)-paroxetine. The accuracy of the method was 102.3% (mean value) for trans-(-)-paroxetine and 99.9% (mean value) for trans-(+)-paroxetine. For the precision (repeatability), a relative standard deviation value of 1.5% (mean value) for trans-(-)-paroxetine and of 2.1% (mean value) for trans-(+)-paroxetine was found. The method is capable of determining a minimum limit of 0.2% of trans-(+)-isomer in commercial samples.

Simultaneous measurement of serotonin and paroxetine in rat brain microdialysate by a single-pump column-switching technique

Simultaneous quantitation of paroxetine and serotonin in rat brain microdialysate is presented as a means to study the neuropharmacokinetics and neuropharmacodynamics of paroxetine, a selective serotonin reuptake inhibitor. In order to achieve this objective, a single-pump column-switching technique was developed. Optimization of the mobile phase in terms of the concentration of ion-pairing agent, pH of mobile phase, temperature of the stationary phase and concentration of organic modifier was investigated and a single mobile phase was developed for both separations. The design was such that the switching valve employed column I (50 mm length) and column II (250 mm length) in series in position A. At 15.3 min, the valve was switched to position B, in which the flow of the mobile phase was directed only through the short column (column I). A flow gradient program was used to increase the flow-rate from 0.125 ml/min to 0.4 ml/min, which enabled a reduction in total analysis time to less than 20 min. The limits of detection for serotonin and paroxetine were 6 fmol and 300 fmol, respectively. The accuracy of the method demonstrated percent differences from spiked samples that were within 12.5% and the precision was found to be within 10% R.S.D.