Determination of sertraline and desmethylsertraline in human serum using copolymeric bonded-phase extraction, liquid chromatography and gas chromatography-mass spectrometry

Estimation of sertraline by chromatographic (HPLC-UV273 nm) technique under hydrolytic stress conditions

Purpose:

In this paper, simple, specific and accurate RP-HPLC method was developed in order to study decomposition of sertraline (SRT) under the hydrolytic stress conditions (acid, neutral, alkaline and oxidative).

Materials and Methods:

The best separation of SRT and its degradation products were achieved on reverse phase LiChoCART with Purospher (RP-18e) column. The mobile phase was composed of methanol/water (75:25, v/v). The detection wavelength was 273 nm. The method was validated and response was found to be linear in the drug concentration range of 10–200 μg ml–1 with correlation coefficient of 0.998.

Results:

The RSD values for intra- and inter-day precision were < 0.65 and < 0.72%, respectively. Employing RP-HPLC method, degradation products were detected in the exposed samples.

Conclusion:

It was found that the susceptibility of SRT to hydrolytic decomposition increased in following manner: Neutral condition < alkaline condition < acid condition < oxidative condition.

Development and validation of stability indicating method for determination of sertraline following ICH guidlines and its determination in pharmaceuticals and biological fluids

BACKGROUND

Sertraline is a well known antidepressant drug which belongs to a class called selective serotonin reuptake inhibitor. Most published methods do not enable studying the stability of this drug in different stress conditions.

RESULTS

Two new methods were developed for the determination of sertraline (SER). Both methods are based on coupling with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) in borate buffer of pH 7.8 and measuring the reaction product spectrophotometrically at 395 nm (Method I) or spectrofluorimetrically at 530 nm upon excitation at 480 nm (Method II). The response-concentration plots were rectilinear over the range 2-24 μg/mL and 0.25-5 μg/mL for methods I and II respectively with LOD of 0.18 μg/mL and 0.07 μg/mL, and LOQ of 0.56 μg/mL and 0.21 μg/mL for methods I and II, respectively.

CONCLUSION

Both methods were applied to the analysis of commercial tablets and the results were in good agreement with those obtained using a reference method. The fluorimetric method was further applied to the in vivo determination of SER in human plasma. A proposal of the reaction pathway was presented. The spectrophotometric method was extended to stability study of SER. The drug was exposed to alkaline, acidic, oxidative and photolytic degradation according to ICH guidelines. Moreover, the method was utilized to investigate the kinetics of oxidative degradation of the drug. The apparent first order rate constant and t1/2 of the degradation reaction were determined.

Hollow fiber-based liquid phase microextraction combined with high-performance liquid chromatography for extraction and determination of some antidepressant drugs in biological fluids

The applicability of hollow fiber-based liquid phase microextraction (HF-LPME) was evaluated for the extraction and preconcentration of three antidepressant drugs (amitriptyline, imipramine and sertraline) prior to their determination by HPLC-UV. The target drugs were extracted from 11.0 mL of aqueous solution with pH 12.0 (source phase) into an organic extracting solvent (n-dodecane) impregnated in the pores of a hollow fiber and finally back extracted into 24 microL of aqueous solution located inside the lumen of the hollow fiber and adjusted to pH 2.1 using 0.1M of H3PO4 (receiving phase). The extraction was performed due to pH gradient between the inside and outside of the hollow fiber membrane. In order to obtain high extraction efficiency, the parameters affecting the HF-LPME including pH of the source and receiving phases, the type of organic phase, ionic strength and volume of the source phase, stirring rate and extraction time were studied and optimized. Under the optimized conditions, enrichment factors up to 300 were achieved and the relative standard deviation (R.S.D.%) of the method was in the range of 2-12%. The calibration curves were obtained in the range of 5-500 microg L(-1) with reasonable linearity (R2>0.998) and the limits of detection (LODs) ranged between 0.5 and 0.7 microg L(-1) (based on S/N=3). Finally, the applicability of the proposed method was evaluated by extraction and determination of the drugs in urine, plasma and tap water samples. The results indicated that hollow fiber microextraction method has excellent clean-up and high-preconcentration factor and can be served as a simple and sensitive method for monitoring of antidepressant drugs in the biological samples.

HPLC analysis of the second-generation antidepressant sertraline and its main metabolite N-desmethylsertraline in human plasma

A liquid chromatographic method with ultraviolet detection was developed for the analysis of the recent antidepressant sertraline and its main metabolite N-desmethylsertraline in human plasma. The analytes were separated on a C8 reversed phase column, using a mobile phase composed of acetonitrile and a 12.3 mM, pH 3.0 phosphate buffer containing 0.1% triethylamine (35:65, v/v). Clomipramine was used as the Internal Standard. Using a solid phase extraction procedure with C2 cartridges high extraction yields (>94%) and good purification from matrix interference were obtained. Good linearity was obtained in the 7.5-250.0 ng mL(-1) range for sertraline and in the 10-500 ng mL(-1) range for N-desmethylsertraline. The analytical method was validated in terms of precision, extraction yield and accuracy. These assays gave R.S.D.% values for precision always lower than 3.9% and mean accuracy higher than 90%. Thanks to its good selectivity, the method proved to be suitable for the analysis of plasma samples from patients treated with sertraline as either monotherapy or polypharmacy.

Development and validation of a liquid chromatographic/tandem mass spectrometric method for the determination of sertraline in human plasma

A sensitive and rapid liquid chromatographic/tandem mass spectrometric method was developed and validated for the determination of sertraline in human plasma. The analyte and internal standard (IS, diphenhydramine) were extracted with 3 mL of diethyl ether/dichloromethane (2:1, v/v) from 0.25 mL plasma, then separated on a Zorbax Eclipse XDB C18 column using methanol/water/formic acid (75:25:0.1, v/v/v) as the mobile phase. The triple quadrupole mass spectrometry was applied via an atmospheric pressure chemical ionization (APCI) source for detection. The fragmentation pattern of the protonated sertraline was elucidated with the aid of product mass spectra of isotopologous peaks. Quantification was performed using selected reaction monitoring of the transitions of m/z 306 --> 159 for sertraline and m/z 256 --> 167 for the IS. The method was linear over the concentration range of 0.10-100 ng/mL. The intra-day and inter-day precisions, expressed by relative standard deviation, were both less than 6.7%. Assay accuracies were within +/-6.9% as terms of relative error. The lower limit of quantification (LLOQ) was identifiable and reproducible at 0.10 ng/mL with a precision of 8.3% and an accuracy of 9.6%. The validated method has been successfully applied for the pharmacokinetic study and bioequivalence evaluation of sertraline in 18 healthy volunteers after a single oral administration of 50 mg sertraline hydrochloride tablets.

Rapid and sensitive method for the determination of sertraline in human plasma using liquid chromatography–tandem mass spectrometry (LC–MS/MS)

A method for the determination of sertraline, a new antidepressant drug and a selective serotonin reuptake inhibitor (SSRI), in human plasma is described. Therapeutic drug monitoring (TDM) necessitates efficient, fast and reliable analytical methods validated by external quality control. We therefore devised a simple, rapid and sensitive isocratic reversed-phase liquid chromatographic-tandem mass spectrometric method equipped with Turbo Ion spray (TIS) source, operating in the positive ion and selective reaction monitoring (SRM) acquisition mode to quantify sertraline in human plasma. A new and superior procedure of solid-phase extraction (SPE) (compared to liquid-liquid extraction) was followed to extract sertraline and imipramine as internal standard (IS) from the human plasma. Sample preparation was performed using waters hydrophilic-lipophilic balance (HLB) cartridge and this method yielded extremely clean extracts with very good recovery, 81.47 and 85.79% for sertraline and IS, respectively. Both were analyzed by combined reverse phase liquid chromatography and tandem mass spectrometry (LC-MS/MS) with positive ion TIS ionization using SRM acquisition mode. The response of the LC-MS/MS method for sertraline was linear over the dynamic range of 0.5-60.0 ng/ml with correlation coefficient r>or=0.9996. The coefficient of variance (%CV) was 8.53% at 0.5 ng/ml and the accuracy was well within the accepted limit of +/-20% at lower limit of quantification (LLOQ) and +/-15% at all the other concentrations in the linear range. This method was fully validated for the accuracy, precision and stability studies. The above findings indicate that the method is very much accurate and precise and can be successfully applied for bioequivalence studies in human subjects.

Electroanalytical study of the antidepressant sertraline

A flow injection square wave cathodic stripping voltammetric method has been developed for the determination of sertraline in a pharmaceutical preparation. The method shows linearity between peak current intensity and sertraline concentration for the interval between 0.20 x 10(-6) and 1.20 x 10(-6) mol L(-1). Limits of detection and quantification were found to be 1.5 x 10(-7) and 5.0 x 10 (-7) mol L(-1), respectively. Up to 70 samples per hour can be analysed with a good precision (R.S.D. = 2.5%). The proposed method was successfully applied to the determination of sertraline in a commercial product. In the voltammetric determination of sertraline in flow, a high sample rate is obtained at reduced costs, opening the possibility to compete with the chromatographic methods generally used for this analysis.

A high-performance liquid chromatography method with photodiode-array UV detection for therapeutic drug monitoring of the nontricyclic antidepressant drugs

A new rapid and sensitive high-performance liquid chromatography method has been developed for the screening and determination in human plasma of the 11 most commonly prescribed nontricyclic antidepressants and two metabolites: fluoxetine, norfluoxetine, sertraline, paroxetine, citalopram, fluvoxamine, moclobemide, mirtazapine, milnacipram, toloxatone, venlafaxine, desmethyl venlafaxine, and viloxazine. It involves liquid-liquid extraction procedures followed by liquid chromatography coupled to photodiode-array UV detection with three fixed wavelengths (220, 240, and 290 nm). Compounds were separated on a 5-microm Hypurity C18 (ThermoHypersil) analytic column (250 x 4.6 mm i.d.) using a gradient of acetonitrile-phosphate buffer pH 3.8 at a flow rate of 1.0 mL/min. The total analysis time was only 18 min per sample. Extraction recoveries were in the 74-109% range for 11 compounds but were of only 59% for moclobemide and less than 10% for toloxatone. Calibration curves were linear in the 25 to 1000 ng/mL range for all compounds, all of them with coefficients of determination (r2 values) > or = 0.999. Limits of detection (LODs) ranged from 2.5 to 5 ng/mL except for toloxatone (10 ng/mL). Intraassay and interassay precision and accuracy were studied at two concentration levels (50 and 500 ng/mL). The intraassay coefficients of variation (CVs) for all compounds were < or = 7.6%, and all interassay CVs were below 11.5% except for milnacipram (14.8%). The intraassay and interassay accuracies for all compounds were found to be within 88.4% and 105.9% at 50 ng/mL and within 87.2% and 100.5% at 500 ng/mL. The performance of the method allows the therapeutic drug monitoring of the most prescribed nontricyclic antidepressant drugs as well as its use in toxicologic screening.

HPLC determination of sertraline in bulk drug, tablets and capsules using hydroxypropyl-β-cyclodextrin as mobile phase additive

A sensitive and stereospecific high-performance liquid chromatography (HPLC) method for determination of sertraline in bulk drug, tablets and capsules was developed. Chromatography resolution of the sertraline enantiomeric forms and trans diastereoisomers was performed on Alltima C18 (250 mm x 4.6mm i.d., 5 microm) column with hydroxypropyl-beta-cyclodextrin (HP-beta-CD) as mobile phase additive. The composition of the mobile phase was 68:32 (v/v) aqueous 170 mM phosphate buffer, pH 3.0 (adjusted with 85% phosphoric acid) containing 18 mM HP-beta-CD/acetonitrile at a flow rate of 1.0 ml x min(-1). The UV detector was set at 225 nm. Calibration curves were linear (r=0.9999, n=9) in the range of 1-120 microgml (-1) for sertraline. Limit of detection and quantitation for sertraline was 0.029 and 0.097 microg x ml (-1). The values of R.S.D. of repeatability and intermediate precision for bulk drug, tablets and capsules of sertraline hydrochloride were less than 1.0%.

Rapid and simple methods for quantitative analysis of some antidepressant in pharmaceutical formulations by using first derivative spectrophotometry and HPLC

Two rapid, simple and accurate first derivative spectrophotometry and HPLC method for the determination of nefazodone hydrochloride and sertraline hydrochloride in pharmaceutical formulations are discussed. The first one is a derivative spectrophotometric procedure and the second one is based on a HPLC method with a UV detector. In the first method, first derivative spectrophotometry, nefazodone hydrochloride or sertraline hydrochloride by measurement of their first derivative signals at 241.8-256.7 nm (peak-to-peak amplitude), or 271.6-275.5 nm (peak-to-peak amplitude), respectively. Calibration graphs were established for 10.0-42.0 microg ml(-1) nefazodone hydrochloride, or 8.0-46.0 microg ml(-1) sertraline hydrochloride. In the other method, HPLC, the UV detection was carried out at 265.0 nm (nefazodone hydrochloride) and 270.0 nm (sertraline hydrochloride). The samples were chromatographed on a Supercosil RP-18 column. The mobile phases were methanol:acetonitrile:phosphate buffer at pH 5.5 (10:50:40 v/v/v) (nefazodone hydrochloride) and methanol:phosphate buffer at pH 4.5 (20:80 v/v) (sertraline hydrochloride). The results obtained from first derivative spectrophotometric method were comparable with those obtained by using HPLC. It was concluded that both the developed methods are equally accurate, sensitive, and precision could be applied directly and easily to the pharmaceutical formulations of nefazodone hydrochloride and sertraline hydrochloride, respectively.

Clinical pharmacokinetics of sertraline

Sertraline is a naphthalenamine derivative with the predominant pharmacological action of inhibiting presynaptic reuptake of serotonin from the synaptic cleft. It was initially marketed for the treatment of major depressive disorder and is now approved for the management of panic disorder, obsessive-compulsive disorder and post-traumatic stress disorder. Sertraline is slowly absorbed following oral administration and undergoes extensive first-pass oxidation to form N-desmethyl-sertraline, a weakly active metabolite that accumulates to a greater concentration in plasma than the parent drug at steady state. Sertraline is eliminated from the body by other metabolic pathways to form a ketone and an alcohol, which are largely excreted renally as conjugates. The elimination half-life of sertraline ranges from 22-36 hours, and once-daily administration is therapeutically effective. Steady-state plasma concentrations vary widely, up to 15-fold, in patients receiving usual antidepressant dosages between 50 and 150 mg/day. However, only sparse data have been published that support useful correlations between sertraline plasma concentrations and therapeutic or adverse effects to justify therapeutic drug monitoring. Sertraline has minimal inhibitory effects on the major cytochrome P450 enzymes, and few drug-drug interactions of clinical significance have been documented. Like other selective serotonin reuptake inhibitors, sertraline is well tolerated in therapeutic dosages and relatively safe in overdosage.

Rapid and sensitive determination of sertraline in human plasma using gas chromatography-mass spectrometry

A method for the determination of sertraline in human plasma using gas chromatography-mass spectrometry (GC-MS), with the selected ion-monitoring (SIM) mode, was described. The following was used in this study: (1) single liquid-liquid extraction at alkaline pH after deproteinization of plasma protein and (2) perfluoroacylation with HFBA, which has higher sensitivity (about 10-fold) compared with previous reported derivatization. The detection limit for the SIM of sertraline as an N-HFB derivative was 0.1 ng/ml, and its recovery was 80-85%. The linear response was obtained in the range of 0.2-10.0 ng/ml with a correlation coefficient of 0.999. The coefficient of variation (C.V.%) was less than 12.1% in the 1-30 ng/ml, and less than 18.2% at 0.2 ng/ml, and the accuracy was less than 10% at all of the concentration range. These findings indicate that this assay method has adequate precision and accuracy to determine the amount of sertraline in human plasma. After pharmacokinetics was performed with this assay method following oral administration of sertraline hydrochloride in man, moment analysis revealed that pharmacokinetic parameters for sertraline (Cmax, 10.3 ng/ml; Tmax, 8.0 h; T(1/2) 28.6 h) were similar to previously reported results. These results indicate that this simple and sensitive assay method is readily applicable to the pharmacokinetic studies of sertraline.

Methods for the determination of seven selective serotonin reuptake inhibitors and three active metabolites in human serum using high-performance liquid chromatography and gas chromatography

This paper describes a set of simple and sensitive multiresidue methods for the determination of the specific serotonin reuptake inhibitors (SSRIs) used as antidepressant drugs, and some of their respective active metabolites in human serum. It involves liquid-liquid extraction procedures followed by gas chromatography coupled to nitrogen phosphorus detection or isocratic reversed-phase high-performance liquid chromatography combined with fluorescence detection (HPLC-FL), depending on the analytes. Extraction recoveries were between 71 and 96% for the eight SSRIs and their metabolites analysed by GC and between 41 and 77% for the two of them analysed by HPLC. Limits of detection (LODs) and limits of quantitation (LOQs) ranged, respectively, from 2.5 to 5 microg/l and from 10 to 20 microg/l. Intra-assay and inter-assay precision was studied at three and four concentration levels, respectively, and was less than 19% for all compounds. Accuracy was also satisfactory for all. An excellent linearity was observed from the LOQs up to 1000 microg/l for milnacipram and paroxetine and from each LOQ up to 400 mg/l for the other compounds. The performance of the methods described thus allows the therapeutic drug monitoring of the currently commercialised SSRIs.

Is therapeutic drug monitoring a case for optimizing clinical outcome and avoiding interactions of the selective serotonin reuptake inhibitors?

The selective serotonin reuptake inhibitors (SSRIs) comprise citalopram, fluoxetine, fluvoxamine, paroxetine, and sertraline and they differ from each other in chemical structure, by pharmacokinetic properties and, most importantly, with respect to enzyme-specific metabolism and interactions. Citalopram is administered as a racemic mixture. The drug is oxidated to desmethylcitalopram in the liver, partially by CYP2C19 and partially by CYP3A4. Fluoxetine is administered as a racemate of R- and S-fluoxetine. Both R- and S-fluoxetine are metabolized by CYP2D6 to the active metabolites R- and S-norfluoxetine. Fluvoxamine is metabolized to inactive metabolites by CYP1A2 and CYP2D6. Paroxetine is metabolized to inactive metabolites partially by CYP2D6, and accordingly the metabolism of paroxetine is dependent on the genetic polymorphism of CYP2D6. Sertraline is metabolized to desmethylsertraline, probably by CYP3A4. Several analytical methods have been described for all SSRIs. Most assays are based on separation by high-performance liquid chromatography or gas chromatography. Stereoselective methods for the analysis of racemic citalopram and fluoxetine have been published. The SSRIs are generally well tolerated and their therapeutic indices are large. In several studies there has not been found a clear relationship between clinical efficacy and plasma concentration, nor any threshold that defines toxic concentrations. The available data do not suggest that any benefit be obtained from routine monitoring of SSRI plasma levels. Therefore therapeutic drug monitoring (TDM) of the SSRIs may be useful mainly in situations where poor compliance is suspected and when therapeutic failure or toxic events are experienced at clinically relevant dosages. Further, in special populations, such as in elderly patients, poor metabolizers of sparteine (CYP2D6) or mephenytoin (CYP2C19), and patients with liver impairment, the measurement of plasma concentrations may be useful.

Analysis of cis-trans isomers and enantiomers of sertraline by cyclodextrin-modified micellar electrokinetic chromatography

In this work development, optimization and validation of a cyclodextrin-modified micellar electrokinetic chromatography (CD-modified MEKC) method is proposed to resolve separation of the sertraline hydrochloride and synthesis-related substances. Sertraline hydrochloride, the cis-(1S,4S) enantiomer form, is used as an antidepressant therapeutic agent. A buffer concentration composed of 20 mM sodium borate, pH 9.0 with 50 mM sodium cholate, 15 mM sulfated beta-cyclodextrin and 5 mM hydroxypropyl-beta-cyclodextrin was found to be the most suitable background electrolyte. Quantitation of the impurities at levels of 0.1% in different samples of the bulk drug was determined. A comparison of the results with those obtained by HPLC methodology was also accomplished. The method proved appropriate for testing the purity of sertraline hydrochloride in bulk drug.

Spectrophotometric determination of fluoxetine and sertraline using chloranil, 2, 3 dichloro-5, 6 dicyano benzoquinone and iodine

Spectrophotometric procedures are presented for the determination of two commonly used antidepressant drugs, fluoxetine (I) and sertraline hydrochloride (II). The methods are based mainly on charge transfer complexation reaction of these drugs with either pi acceptors chloranil and 2, 3 dichloro-5, 6-dicyanoquinone (DDQ) or sigma acceptor iodine. The colored products are quantified spectrophotometrically at 550, 450 and 263 nm for fluoxetine and at 450, 455 and 290 nm for sertraline in chloranil, DDQ and iodine methods, respectively. The molar combining ratio and the optimum assay conditions were studied. The methods determine the cited drugs in concentration ranges of 8-640, 16-112 and 7.5-60 microg/ml with mean percentage recoveries of 99.83, 99.76 and 100.00% and R.S.D. of 1.24, 0.95 and 1.13% in fluoxetine and ranges of 16-160, 15-105 and 6-48 microg/ml with mean percentage recoveries of 100.39, 99.78 and 99.69% and R.S.D. of 1.02, 0.81 and 0.57% in sertraline for chloranil, DDQ and iodine methods, respectively. A more detailed investigation of the complex formed was made with respect to its composition, association constant K(AD)c, molar absorptivity xiAD(A) and free energy change deltaG. The proposed methods were applied successfully to the determination of the cited drugs either in pure or dosage forms with good accuracy and precision. The results were compared statistically with those given by the reported methods.

Metabolism and pharmacokinetics of selective serotonin reuptake inhibitors

1. Five drugs with the predominant pharmacologic effect of inhibiting the neuronal reuptake of serotonin are available worldwide for clinical use. This class of psychoactive drugs, known as selective serotonin reuptake inhibitors (SSRIs), is comprised of fluoxetine, sertraline, paroxetine, fluvoxamine, and citalopram. 2. The SSRIs appear to share similar pharmacodynamic properties which translate to efficacy in the treatment of depression and anxiety syndromes. The drugs are differentiated by their pharmacokinetic properties with regard to stereochemistry, metabolism, inhibition of cytochrome enzymes, and participation in drug-drug interactions. Studies focusing on the relationship of plasma drug concentration to therapeutic and adverse effects have not confirmed the value of plasma concentration monitoring. 3. This review summarizes the metabolism and relevant pharmacokinetic properties of the SSRIs.

The extent and determinants of changes in CYP2D6 and CYP1A2 activities with therapeutic doses of sertraline

The extent of changes in CYP2D6 and CYP1A2 activities with higher therapeutic dosages (>50 mg/day) of sertraline is not well established in vivo. This study assessed the extent and determinants of changes in CYP2D6 and CYP1A2 isozyme activities after treatment with clinically relevant doses of sertraline. Patients and healthy volunteers aged 19 to 85 years (N = 21) were treated with sertraline for 5 to 55 days. The dosage of sertraline ranged from 25 to 150 mg/day (93.5+/-26.4 mg/day; mean +/- SD). All subjects had an extensive metabolizer phenotype for CYP2D6 and received a single oral dose of dextromethorphan (30 mg) and caffeine (100 mg) before and after sertraline treatment. The log O-demethylation ratio (ODMR) of dextromethorphan and the caffeine metabolic ratio (CMR) in overnight urine were used as in vivo indices of the CYP2D6 and CYP1A2 isozyme activities, respectively. Concurrent medications and lifestyle habits (e.g., smoking and diet) were monitored during the study. Baseline log ODMR (-2.33+/-0.45) but not CMR (5.1+/-1.9) (mean +/- SD) significantly changed after sertraline treatment (-2.19+/-0.62; 4.5+/-1.6, respectively) (p: ODMR = 0.04, CMR = 0.10). There was no significant effect of age, dose, duration of treatment, gender, sertraline and/or desmethylsertraline plasma concentration, subject type (patient or volunteer), and weight on the extent of changes in log ODMR or CMR (p > 0.05). In conclusion, sertraline treatment at a mean daily dosage of 94.0 mg did not significantly change CYP1A2 activity and resulted in a modest inhibition of CYP2D6 activity.

Pharmacokinetic-pharmacodynamic relationship of the selective serotonin reuptake inhibitors

The recently introduced antidepressants, the selective serotonin reuptake inhibitors (SSRIs) [citalopram, fluoxetine, fluvoxamine, paroxetine and sertraline], are known for their clinical efficacy, good tolerability and relative safety. They differ from each other in chemical structure, metabolism and pharmacokinetic properties. Therapeutic drug monitoring of these compounds is not widely used, as the plasma concentration ranges within which clinical response with minimal adverse effects appears to be optimal are not clearly defined. Almost all recent assays developed for the quantitative determination of SSRIs and their metabolites in blood are based either on the separation of SSRIs by high performance liquid chromatography (HPLC) or gas chromatography (GC). Citalopram and fluoxetine have been introduced as racemic compounds. There are some differences in the pharmacological profile, metabolism and pharmacokinetics between the enantiomers of the parent compounds and their demethylated metabolites. Stereoselective chromatographic methods for their analysis in blood are now available. With regard to the SSRIs presently available, no clearcut plasma concentration-clinical effectiveness relationship in patients with depression has been shown, nor any threshold which defines toxic concentrations. This may be explained by their low toxicity and use at dosages where serious adverse effects do not appear. SSRIs vary widely in their qualitative and quantitative interaction with cytochrome P450 (CYP) isozymes in the liver. CYP2D6 is inhibited by SSRIs, in order of decreasing potency paroxetine, norfluoxetine, fluoxetine, sertraline, citalopram and fluvoxamine. This may have clinical consequences with some but not all SSRIs, when they are taken with tricyclic antidepressants. Except for citalopram and paroxetine, little is known about the enzymes which control the biotransformation of the SSRIs. There have been many reports on marked pharmacokinetic interactions between fluoxetine and tricyclic antidepressants. Fluoxetine has a stronger effect on their hydroxylation than on their demethylation. Interactions observed between fluoxetine and alprazolam, midazolam and carbamazepine seem to occur on the level of CYP3A. Fluvoxamine strongly inhibits the N-demethylation of some tricyclic antidepressants of the tertiary amine type and of clozapine. This may lead to adverse effects but augmentation with fluvoxamine can also improve response in very rapid metabolisers, as it increases the bioavailability of the comedication. Fluvoxamine inhibits with decreasing potency, CYP1A2, CYP2C19, CYP2D6 and CYP1A1, but it is also an inhibitor of CYP3A. Fluoxetine and fluvoxamine have shown to increase methadone plasma concentrations in dependent patients. Some authors warn about a combination of monoamine oxidase (MAO) inhibitors with SSRIs, as this could lead to a serotonergic syndrome. Studies with healthy volunteers suggest, however, that a combination of moclobemide and SSRIs, such as fluvoxamine, should not present serious risks in promoting a serotonin syndrome. A combination of moclobemide and fluvoxamine has successfully been used in refractory depression, but more studies are needed, including plasma-concentration monitoring, before this combined treatment can be recommended. Paroxetine is a substrate of CYP2D6, but other enzyme(s) could also be involved. Its pharmacokinetics are linear in poor metabolisers of sparteine, and non-linear in extensive metabolisers. Due to its potent CYP2D6 inhibiting properties, comedication with this SSRI can lead to an increase of tricyclic antidepressants in plasma, as shown with amitriptyline and trimipramine. CYP3A has been claimed to be involved in the biotransformation of sertraline to norsertraline. Clinical investigations (with desipramine) confirmed in vitro findings that CYP2D6 inhibition by sertraline is only moderate. (ABSTRACT TRUNCATED)

Analytical methods for the quantitative determination of selective serotonin reuptake inhibitors for therapeutic drug monitoring purposes in patients

Five selective serotonin reuptake inhibitors (SSRIs) have been introduced recently: citalopram, fluoxetine, fluvoxamine, paroxetine and sertraline. Although no therapeutic window has been defined for SSRIs, in contrast to tricyclic antidepressants, analytical methods for therapeutic drug monitoring of SSRIs are useful in several instances. SSRIs differ widely in their chemical structure and in their metabolism. The fact that some of them have N-demethylated metabolites, which are also SSRIs, requires that methods be available which allow therapeutic drug monitoring of the parent compounds and of these active metabolites. most procedures are based on prepurification of the SSRIs by liquid-liquid extraction before they are submitted to separation by chromatographic procedures (high-performance liquid chromatography, gas chromatography, thin layer chromatography) and detection by various detectors (UV, fluorescence, electrochemical detector, nitrogen-phosphorus detector, mass spectrometry). This literature review shows that most methods allow quantitative determination of SSRIs in plasma, in the lower ng/ml range, and that they are, therefore, suitable for therapeutic drug monitoring purposes of this category of drugs.

HPLC of sertraline and norsertraline in plasma or serum

A simple method for the measurement of sertraline and norsertraline in plasma or serum suitable for use in single-dose pharmacokinetic studies has been developed. Internal standard solution, aqueous fenethazine (10 mg/L) (20 microL), and Tris buffer (2 mol/L), pH 10.6) (100 microL) were added to plasma (200 microL). Sertraline, norsertraline and the internal standard were extracted into methyl tert-butyl ether (200 microL) by mixing (30 s) and centrifugation (11,000 r.p.m., 4 min). A portion (100 microL) of the extract was injected onto a Spherisorb S5SCX HPLC column (150 x 4.6 mm i.d.) which was eluted with methanol:water (19 + 1) containing ammonium perchlorate (40 mmol/L), final pH 7.0. Detection was by UV monitoring (215 nm). The concentration of each analyte in each sample was calculated from the calibration graph (peak-height ratio of analyte to that of the internal standard against concentration) obtained after analysis of plasma samples containing known amounts of sertraline and norsertraline. The limit of accurate measurement of the assay was 10 micrograms/L) sertraline and 20 micrograms/L) norsertraline.