Therapeutic drug monitoring: chemical-clinical correlations of atypical antipsychotic drugs

Selective Spectrofluorimetric Approach for the Assessment of Two Antipsychotic Drugs through Derivatization with O-Phthalaldehyde

A facile and sensible spectrofluorimetric approach for the measurement of two antipsychotic medications, aripiperazole (ARP) and clozapine (CLZ), was devised and validated. The approach involves reacting the examined medicines with o-phthalaldehyde in the presence of β-mercaptoethanol in a borate buffer of pH 9.0 and pH 10 for ARP and CLZ, respectively, to produce a robustly fluorescent compound that is detected at 450 nm following excitation at 340 nm. The experimental variables influencing the performance and product stability were thoroughly investigated and optimized. Under optimal conditions, the intensity of the fluorescence was linear during a concentration range of 0.1–0.5 μg/mL, with a limit of detection (0.0391 and 0.0400 μg/mL) and limit of quantitation (0.1035 and 0.1332 μg/mL), respectively, for ARP and CLZ. The suggested approach was successful in analyzing commercialized tablets. A statistical investigation of the results produced by the suggested and standard methods showed no remarkable variation in the precision and accuracy of the two approaches. A chemical mechanism using o-phthalaldehyde was proposed.

Dried Volumetric Microsampling Approaches for the Therapeutic Drug Monitoring of Psychiatric Patients Undergoing Clozapine Treatment

Clozapine is one of the most widely used second-generation antipsychotic drugs (SGAs) for the treatment of schizophrenia. Despite advantages over first-generation drugs, clozapine still shows significant side effects and interindividual variations in efficacy. In order to ensure frequent therapeutic drug monitoring (TDM) and improve the compliance of psychiatric patients undergoing clozapine treatment, two novel dried microsampling approaches based on whole blood and plasma volumetric absorptive microsampling (b-VAMS and p-VAMS) and microfluidic generated-dried blood spot technology (mfDBS) were developed and coupled to HPLC with electrochemical detection (ED). The proposed miniaturized strategies by means of VAMS and microfluidic channel-based devices provide several advantages in terms of collection, storage, and handling compared to classical blood and plasma processing. Satisfactory validation results were obtained for all microsampling platforms, with mean extraction yields >85.1%, precision as relative standard deviation (RSD) < 5.1%, and stability < 4.5% analyte loss after 30 days for p-VAMS; mean extraction yields > 83.4%, precision RSD < 5.4%, and stability < 4.6% analyte loss after 30 days for b-VAMS, and mean extraction yields > 74.0%, precision RSD < 5.6%, and stability < 4.9% analyte loss after 30 days for mfDBS. The original microsampling methodologies have been successfully applied to the blood and plasma collected from five psychiatric patients for the monitoring of the levels of clozapine and its main metabolites, providing robust and reliable quali-quantitative results. Comparisons between results of the two dried microsampling technologies with those obtained by classic fluid plasma analysis were in good agreement and have demonstrated that the proposed miniaturized approaches could be suitable for TDM purposes.

Multiplexed therapeutic drug monitoring of antipsychotics in dried plasma spots by LC-MS/MS

In this work, a convenient method for the therapeutic monitoring of seven common antipsychotic drugs in "dried plasma spot" samples has been developed. It is based on the liquid chromatography tandem mass spectrometry technique, operating in multiple reaction monitoring mode, and a straightforward procedure for the simultaneous extraction of all antipsychotics in a single step, with high extraction yield. The method was fully validated with proper accuracy, precision, selectivity and sensitivity, for all the drugs. Limits of quantification were 0.12, 1.09, 1.46, 1.47, 5.70, 1.32, 1.33 µg/L for haloperidol, aripiprazole, olanzapine, quetiapine, clozapine, risperidone, and paliperidone, respectively. Accuracy, intra- and interday precision values were <10% for all drugs at all concentration levels examined. The method was tested in the analysis of 30 plasma samples from real patients for each drug. The proposed analytical approach, by combining practical and logistical advantages of microsampling with liquid chromatography tandem mass spectrometry analytical performance, could offer an ideal strategy for accurate and timely therapeutic drug monitoring of antipsychotic drugs in most clinical settings, even in remote centers and/or in out-patient settings, bringing so many potential improvements in psychiatric patient care.

Antipsychotic drug poisoning monitoring of clozapine in urine by using coffee ring effect based surface-enhanced Raman spectroscopy

Antipsychotics are the drugs most often involved in drug poisoning cases, and therefore, therapeutic drug monitoring (TDM) is necessary for safe and effective medication administration of these drugs. In this study, a coffee ring effect-based surface-enhanced Raman spectroscopy (CRE-SERS) method was developed and successfully used to monitor antipsychotic poisoning by using urine samples for the first time. The established method exhibited excellent SERS performance since more hot spots were obtained in the "coffee ring". Using the optimized CRE-SERS method, the sensitivity was improved one order more than that of the conventional method with reasonable reproducibility. The antipsychotic drug clozapine (CLO) spiked into urine samples at 0.5-50 μg mL^-1 was quantitatively detected, at concentrations above the thresholds for toxicity. The CRE-SERS method allowed CLO and its metabolites to be ultimately distinguished from real poisoning urine samples. The coffee-ring effect would provide more opportunities for practical applications of the SERS-based method. The frequent occurrence of drug poisoning may have created a new area for the application of the CRE-SERS method. It is anticipated that the developed method will also have great potential for other drug poisoning monitoring.

Determination of blood concentration levels of psychotropic medications in Rwandan patients

OBJECTIVES

In Rwanda, no therapeutic monitoring of psychotropic drugs is done. This results in difficult treatment optimisation and exposition to a high risk of toxicity and drug ineffectiveness for patients under treatment. This study aimed to determine blood concentration levels of psychotropic drugs in Rwandan patients and identify problems associated with the lack of therapeutic drug monitoring (TDM) of these drugs.

METHODS

The analysis was performed on 1 ml of serum sample using prazepam as internal standard. Regarding the step of sample preparation, we used a liquid-liquid extraction with a mixture of organic solvents: diethyl ether/dichloromethane/hexane/n-amyl alcohol (50/30/20/0.5:V/V). A Waters Alliance 2695 was used for analysis. The chromatography was run on a Symmetry C8 column and as mobile phase acetonitrile and phosphate buffer (pH 3.8) were used.

RESULTS

Concerning the results, serum samples from 128 patients were analysed. Twenty-one different psychotropic drugs belonging to various pharmacological classes were detected and quantified. Analytical results were put into three categories based upon therapeutic reference ranges (TRR) of various drugs: subtherapeutic, therapeutic and supratherapeutic. For a total of 237 analyses, results within TRR represented 46% while 47 and 8% of results were, respectively, below and above TRR.

CONCLUSION

It was therefore concluded that patients under psychotropic treatment in Rwanda are exposed to both the risk of drug ineffectiveness and the risk of toxicity (54%) with only 46% of results within the TRR. Consequently, TDM is needed to optimise psychotropic treatment in Rwandan patients.

Dried blood spot testing: a novel approach for the therapeutic drug monitoring of ziprasidone-treated patients

Background: A novel analytical approach, based on dried blood spot (DBS) testing, has been developed, validated and applied for the first time to the analysis of ziprasidone (ZPR) for the therapeutic drug monitoring (TDM) of schizophrenic patients. DBS represent a more feasible but reliable matrix, alternative to blood and plasma. Methods: The assays were carried out using an HPLC method with native fluorescence. Blood drops were applied to DBS cards and dried by microwaves, an internal standard solution was added to the DBS and 5-mm punches were cut out for analysis. ZPR was extracted from DBS with methanol, giving good extraction yields, precision and selectivity results. Results: The method was applied with satisfactory results to DBS samples from psychiatric patients to determine ZPR levels for therapy optimization. Conclusion: This innovative methodology provides reliable and significant TDM information, with important advantages over classical blood sampling in terms of collection, storage and processing.

A reliable and rapid tool for plasma quantification of 18 psychotropic drugs by ESI tandem mass spectrometry

A simple liquid chromatographic tandem mass spectrometry (LC-MS/MS) method has been developed for simultaneous analysis of 17 basic and one acid psychotropic drugs in human plasma. The method relies on a protein precipitation step for sample preparation and offers high sensitivity, wide linearity without interferences from endogenous matrix components. Chromatography was run on a reversed-phase column with an acetonitrile-H₂O mixture. The quantification of target compounds was performed in multiple reaction monitoring (MRM) and by switching the ionization polarity within the analytical run. A further sensitivity increase was obtained by implementing the functionality "scheduled multiple reaction monitoring" (sMRM) offered by the recent version of the software package managing the instrument. The overall injection interval was less than 5.5 min. Regression coefficients of the calibration curves and limits of quantification (LOQ) showed a good coverage of over-therapeutic, therapeutic and sub-therapeutic ranges. Recovery rates, measured as percentage of recovery of spiked plasma samples, were ≥ 94%. Precision and accuracy data have been satisfactory for a therapeutic drug monitoring (TDM) service as for managing plasma samples from patients receiving psycho-pharmacological treatment.

A novel electrochemical sensor for assaying of antipsychotic drug quetiapine

A novel electrochemical sensor based on poly(2-hydroxy-5-[(4-sulfophenyl)azo]benzoic acid) film modified glassy carbon electrode for fast and simple quantification of trace amount of quetiapine fumarate (QF) was developed. It exhibits excellent enhancement effects on the electrooxidation of QF facilitating preconcentration of drug molecules on the electrode surface. Based on its strong adsorptive activity, the concentration of QF in pharmaceutical formulations and biological fluids was determined directly by voltammetry with excellent sensitivity and high selectivity. The introduction of carboxylated and sulfonated functionalities in polymer film improves the uniform selectivity for positively charged target QF molecules. The calibration curve is linear in QF concentration range of 8.0 × 10(-8) to 7.5 × 10(-6)M with detection limit 1.9 × 10(-8) and sensitivity 8.96 × 10(5) μA M(-1). The presented sensor has long term stability and good reproducibility with benefits of fast response time, ease of preparation and regeneration of the surface that makes the proposed method useful in the determination of QF in real samples.

Photo-onycholysis caused by olanzapine and aripiprazole

Photo-onycholysis associated with drugs is an uncommon disorder. We report the case of a woman who developed photo-onycholysis on multiple nails after uptake of olanzapine. Substitution of olanzapine with aripiprazole further exacerbated the problem. The possible mechanisms of photo-onycholysis development by modern atypical antipsychotics, modulating dopamine receptors, are discussed.

Iloperidone: a new benzisoxazole atypical antipsychotic drug. Is it novel enough to impact the crowded atypical antipsychotic market?

Iloperidone is a new-generation atypical antipsychotic agent, acting as a serotonin/dopamine (5-HT(2A)/D(2)) antagonist, under development by Vanda Pharmaceuticals for the treatment of schizophrenia, bipolar disorder and other psychiatric conditions. Chemically, iloperidone is a benzisoxazole, like risperidone, and shows a multiple receptor binding profile, sharing this feature with the other atypical antipsychotic agents. Administered orally, the drug is highly bound to plasma proteins and extensively metabolised. Several clinical trials have been carried out, to check efficacy, safety and side effects. In order to introduce iloperidone as an agent for the treatment of schizophrenia, a short overview of the disease and of the most important antipsychotic drugs available or under development will be reported. Iloperidone pharmacokinetics and pharmacodynamics are presented herein, together with an evaluation of clinical safety and efficacy results.

Analysis of the second generation antidepressant venlafaxine and its main active metabolite O-desmethylvenlafaxine in human plasma by HPLC with spectrofluorimetric detection

A high-performance liquid chromatographic method has been developed for the determination of the recent serotonin and norepinephrine reuptake inhibitor (SNRI) venlafaxine and its main active metabolite, O-desmethylvenlafaxine, in human plasma. Separation was obtained by using a reversed-phase column (C8, 150 x 4.6 mm I.D., 5 microm) and a mobile phase composed of 75% aqueous phosphate buffer containing triethylamine at pH 6.8 and 25% acetonitrile. Fluorescence detection was used, exciting at lambda=238 nm and monitoring the emission at lambda=300 nm. Citalopram was used as the internal standard. A careful pre-treatment of plasma samples was developed, using solid-phase extraction with C1 cartridges (100 mg, 1 mL). The limit of quantification (LOQ) was 1.0 ng mL(-1) and the limit of detection (LOD) was 0.3 ng mL(-1) for both analytes. The method was applied with success to plasma samples taken from patients undergoing treatment with venlafaxine. Precision data, as well as accuracy results, were satisfactory and no interference from other drugs was found. Hence, the method is suitable for therapeutic drug monitoring of venlafaxine and its main metabolite in depressed patients' plasma.

Simultaneous determination of five antipsychotic drugs in rat plasma by high performance liquid chromatography with ultraviolet detection

A significant percentage of psychiatric patients who are treated with antipsychotics are treated with more than one antipsychotic drug in the clinic. Thus, it is advantageous to use a rapid and reliable assay that is suitable for determination of multiple antipsychotic drugs in plasma in a single run. A simple and sensitive HPLC-UV method was developed and validated for simultaneous quantification of olanzapine, haloperidol, chlorpromazine, ziprasidone, risperidone and its active metabolite 9-hydroxyrisperidone in rat plasma using imipramine as an internal standard (I.S.). The analytes were extracted from rat plasma using a single step liquid-liquid acid solution back extraction technique with wash procedure, which provided the very clear baseline for blank plasma extraction. The compounds were separated on an Agilent Eclipse XDB C8 (150 mm x 4.6 mm i.d., 5 microm) column using a mobile phase of acetonitrile/30 mM ammonium acetate including 0.05% triethylamine (pH 5.86 adjusted with acetic acid) with gradient elution. All of the analytes were monitored using UV detection. The method was validated and the linearity, lower limit of quantitation (LLOQ), precision, accuracy, recoveries, selectivity and stability were determined. The LLOQ was 2.0 ng/ml and correlation coefficient (R(2)) values for the linear range of 2.0-500.0 ng/ml were 0.998 or greater for all the analytes. The precision and accuracy for intra-day and inter-day were better than 7.44%. The recovery was above 74.8% for all of the analytes. This validated method has been successfully used to quantify the plasma concentration of the analytes for pharmacological and toxicological studies following chronic treatment with antipsychotic drugs in the rat.

Possible levomepromazine-clozapine interaction: two case reports

OBJECTIVE

To report and comment upon two cases of suspected pharmacological interaction between the "classical" neuroleptic levomepromazine (LMP) and the "atypical" antipsychotic clozapine (CLZ).

CASE SUMMARY

The patients who simultaneously took the two drugs had unusually low plasma levels of CLZ and its metabolites, even though they took high doses of CLZ. The patients were considered "non-responders" to the treatment by the psychiatrist. When LMP was withdrawn from the therapy, plasma concentrations of CLZ returned to therapeutic levels and one of the two patients experienced the anticipated therapeutic response.

DISCUSSION

No information can be found in the literature regarding possible interactions between LMP and CLZ. However, the results of the two cases reported herein point out to a possible lack of therapeutic efficacy of CLZ therapy during this kind of polypharmacy.

CONCLUSION

While two cases are too few to draw any conclusion, it would be prudent on the part of psychiatrists to consider a possible drug interaction in patients receiving both CLZ and LMP who fail to respond to the therapy.

Simultaneous analysis of classical neuroleptics, atypical antipsychotics and their metabolites in human plasma

A high-performance liquid chromatographic method has been developed for the simultaneous determination of classical neuroleptics (chlorpromazine, haloperidol, loxapine and clotiapine), atypical antipsychotics (clozapine, quetiapine and risperidone) and their active metabolites (N-desmethylclozapine, clozapine N-oxide and 9-hydroxyrisperidone) in human plasma. Separation was obtained by using a C8 reversed-phase column and a mobile phase composed of 70% aqueous phosphate buffer containing triethylamine at pH 3.0 and 30% acetonitrile. The UV detector was set at 238 nm and amitriptyline was used as the internal standard. A careful pre-treatment procedure of plasma samples was developed, using solid-phase extraction with cyanopropyl cartridges, which gives high extraction yields (>or=93%). The limits of quantitation (LOQ) were always lower than 2.6 ng mL-1 and the limits of detection (LOD) were always lower than 0.9 ng mL-1 for all analytes. The method was applied with success to plasma samples from schizophrenic patients undergoing polypharmacy with two or more different antipsychotics. Precision data and accuracy results were satisfactory and no interference from other central nervous system (CNS) drugs was found. Hence the method is suitable for the therapeutic drug monitoring (TDM) of the analytes in psychotic patients' plasma.

Liquid chromatography/tandem mass spectrometry method for the simultaneous determination of olanzapine, risperidone, 9-hydroxyrisperidone, clozapine, haloperidol and ziprasidone in rat plasma

A simple, sensitive and rapid liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) method was developed and validated for simultaneous quantification of olanzapine, clozapine, ziprasidone, haloperidol, risperidone, and its active metabolite 9-hydroxyrisperidone, in rat plasma using midazolam as internal standard (IS). The analytes were extracted from rat plasma using a single step liquid-liquid extraction technique. The compounds were separated on a Waters Atlantis dC-18 (30 mm x 2.1 mm i.d., 3 microm) column using a mobile phase of acetonitrile/5 mM ammonium formate (pH 6.1 adjusted with formic acid) with gradient elution. All of the analytes were detected in positive ion mode using multiple reaction monitoring (MRM). The method was validated and the specificity, linearity, lower limit of quantitation (LLOQ), precision, accuracy, recoveries and stability were determined. LLOQ was 0.1 ng/mL and correlation coefficient (R(2)) values for the linear range of 0.1-100 ng/mL were 0.997 or greater for all the analytes. The intra-day and inter-day precision and accuracy were better than 8.05%. The relative and absolute recovery was above 77% and matrix effects were low for all the analytes except for ziprasidone. This validated method has been successfully used to quantify the plasma concentration of the analytes after chronic treatment with antipsychotic drugs.

Determination of Olanzapine in rat brain using liquid chromatography with coulometric detection and a rapid solid-phase extraction procedure

A sensitive and selective method was developed for the determination of the antipsychotic drug Olanzapine levels in rat brain tissue, based on HPLC with electrochemical detection. The analyses were carried out on a C8 reversed phase column (150 mm x 4.6 mm, 5 microm), using a mobile phase composed of methanol and a phosphate buffer (44.0 mM, pH 3.5), containing triethylamine (21:79, v/v), flowing at 1.2 mL min(-1). A high sensitivity coulometric detection analytical cell containing two flow-through low volume working electrodes was used: electrode 1 was set at +0.350 V and electrode 2 at -0.200 V. Olanzapine, administered to rats in different doses or in different times, was extracted from tissue homogenate of either the whole brain or specific areas (cortex, hyppocampus, nucleus striatum) with a rapid solid phase extraction procedure (SPE) on Oasis HLB cartridges. The method provided a high extraction yield of Olanzapine and internal standard (2-methylolanzapine) from brain tissue homogenate with absolute recovery values higher than 90.0%. The detector response was linear over a concentration range of 0.2-100.0 ng mL(-1) of Olanzapine. The limit of quantification (LOQ) was 0.2 ng mL(-1). Precision results, expressed by the intra-day and the inter-day relative standard deviation values, were satisfactory, better than 4.6%. Accuracy was satisfactory as well. This method proved to be suitable for the analysis of Olanzapine in rat brain tissues and for the study of distribution and pharmacokinetics of Olanzapine in rat brain after a single treatment with the antipsychotic drug.

Development and validation of a sensitive liquid chromatography/electrospray tandem mass spectrometry assay for the quantification of olanzapine in human plasma

A simple, sensitive and rapid liquid chromatography/electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) method was developed and validated for the quantification of olanzapine, atypical antipsychotic drug, in human plasma using loratadine as internal standard (IS). Following liquid-liquid extraction, the analytes were separated using an isocratic mobile phase on a reverse phase C18 column and analyzed by MS in the multiple reaction monitoring mode using the respective [M+H]+ ions, m/z 313/256 for olanzapine and m/z 383/337 for the IS. The assay exhibited a linear dynamic range of 0.1-30 ng/mL for olanzapine in human plasma. The lower limit of quantification was 100 pg/mL with a relative standard deviation of less than 10%. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. The average absolute recovery of olanzapine from spiked plasma samples was 85.5+/-1.9%. A run time of 2.0 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.

Automated analysis of quetiapine and other antipsychotic drugs in human blood by high performance-liquid chromatography with column-switching and spectrophotometric detection

An automated HPLC method with column switching is described for the determination of quetiapine, clozapine, perazine, olanzapine and metabolites in blood serum. After clean-up on silica C8 material (20 microm particle size) drugs were separated on ODS Hypersil C18 material (5 microm; column size 250 mm x 4.6 mm i.d.) within 25 min and quantified by ultraviolet (UV) detection at 254 nm. The limit of quantification ranged between 10 and 50 ng/ml. At therapeutic concentrations of the drugs, the inter-assay reproducibility was below 10%. Analyses of drug concentrations in serum of 75-295 patients treated with therapeutic doses of the antipsychotic drugs revealed mean+/-S.D. steady state concentrations of 139+/-136 ng/ml for quetiapine, 328+/-195 ng/ml for clozapine, 48+/-27 ng/ml for olanzapine and 71+/-52 ng/ml for perazine. The method was thus suitable for routine therapeutic drug monitoring and may be extended to other drugs.

Automated Determination of Ziprasidone by HPLC With Column Switching and Spectrophotometric Detection

An isocratic high-performance liquid chromatography (HPLC) method with column switching and ultraviolet (UV) detection is described for quantitative analysis of the new antipsychotic drug ziprasidone. After centrifugation of serum or plasma samples and addition of fluperlapine as internal standard, the samples were injected into the HPLC system. On-line sample clean-up was conducted on a column (10 x 4.0 mm ID) filled with silica C8 material (20-microm particle size) using 8% (vol/vol) acetonitrile in deionized water as eluent. Ziprasidone was eluted and separated on ODS Hypersil C18 material (5 microm; column size 250 x 4.6 mm ID) using acetonitrile-water-tetramethylethylendiamine (50:49.6:0.4, vol/vol/vol). The UV detector was set at 254 nm. Ziprasidone was separated within 20 minutes. The limit of quantification was 10 ng/mL. At therapeutic concentrations, the interassay reproducibility (coefficient of variation) of quality control samples was below 10%. The method was found to be robust and stable. More than 100 serum samples could be analyzed without changing the clean-up column and more than 300 samples using the same analytic column. Among multiple drugs tested for interference, only the tricyclic antidepressants trimipramine and clomipramine were found to exhibit retention times similar to that of ziprasidone. The method was applied to analyze ziprasidone concentrations in blood serum of 67 patients treated with 40 to 280 mg ziprasidone per day for at least 7 days (median 120 mg). The median steady-state serum concentration of ziprasidone was 76 ng/mL, and the 25th and 75th percentile were 43 to 131 ng/mL, respectively. Forty to 130 ng/mL may be considered the recommended target plasma concentration range. HPLC with column switching and UV detection as described here is suitable for therapeutic drug monitoring of ziprasidone.

HPLC-DAD determination of plasma levels of the antipsychotic risperidone and its main metabolite for toxicological purposes

A new, rapid analytical method, based on liquid chromatography with diode array detection, has been developed and applied to the determination of risperidone and its main active metabolite 9-hydroxyrisperidone in human plasma. The chromatographic separation was obtained on a C8 (150 x 4.6 mm, 5 microm) column, using a mobile phase composed of acetonitrile (27%) and a pH 3.0 phosphate buffer (73%). A sample clean-up procedure was carried out by using C8 cartridges and eluting the analytes with methanol. The extraction yield was highly satisfactory for both analytes, with average absolute recovery values of about 95%. The experimental conditions permitted the quantitative determination of risperidone and 9-hydroxyrisperidone with high precision (RSD < 3.6%) and satisfactory sensitivity (LOQ = 4 ng mL(-1)). The method was applied to plasma samples from a patient who had tried to poison himself with 150 mg of risperidone, and was undergoing polypharmacy.

Simultaneous determination of clozapine, olanzapine, risperidone and quetiapine in plasma by high-performance liquid chromatography-electrospray ionization mass spectrometry

Clozapine (CLZ), olanzapine (OLZ), risperidone (RIP) and quetiapine (QTP) have been widely used in the treatment of schizophrenia. However, no study (or little study) has been conducted to determine the four drugs simultaneously by the use of high-performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-MS/ESI).

OBJECTIVE

To develop a sensitive method for simultaneous determination of CLZ, OLZ, RIP and QTP in human plasma by HPLC-MS/ESI.

METHODS

The analytes were extracted twice by ether after samples had been alkalinized. The HPLC separation of the analytes was performed on a MACHEREY-NAGEL C(18) (2.0 mm x 125 mm, 3 microm, Germany) column, using water (formic acid: 2.70 mmol/l, ammonium acetate: 10 mmol/l)-acetonitrile (53:47) as mobile phase, with a flow-rate of 0.16 ml/min. The compounds were ionized in the electrospray ionization (ESI) ion source of the mass spectrometer and were detected in the selected ion recording (SIR) mode.

RESULTS

The calibration curves were linear in the ranges of 20-1000 ng/ml for CLZ and QTP, 1-50 ng/ml for OLZ and RIP, respectively. The average extraction recoveries for all the four analysts were at least above 80%. The methodology recoveries were higher than 91% for the analysts. The intra- and inter-day R.S.D. were less than 15%.

CONCLUSION

The method is accurate, sensitive and simple for routine therapeutic drug monitoring (TDM) and for the study of the pharmacokinetics of the four drugs.

Enantioselective determination of the novel antidepressant mirtazapine and its active demethylated metabolite in human plasma by means of capillary electrophoresis

Mirtazapine is a recent noradrenergic and specific serotonergic antidepressant drug. A capillary electrophoretic method has been developed for the enantioseparation and analysis of mirtazapine and its main active metabolite, N-desmethylmirtazapine, in human plasma. For method optimisation several experimental parameters were investigated, such as type and concentration of the chiral selector, buffer pH and capillary temperature. Baseline enantioseparation of the analytes was achieved in 2.5 min in a fused silica capillary (50 microm i.d.; 48.5 cm total length; 8.5 cm effective length) using carboxymethyl-beta-cyclodextrin, dissolved in a background electrolyte consisting of 50 mM phosphate buffer at pH 2.5, as the chiral selector. UV detection was set at 205 nm. A careful pre-treatment of plasma samples was developed, using solid-phase extraction with hydrophilic-lipophilic balance cartridges (60 mg, 3 mL), eluting the sample with methanol, then concentrating it 37.5 times before injection. Extraction yield values are very satisfactory, being the average 89% for mirtazapine and 73% for N-desmethylmirtazapine. Application of the method to some human plasma samples has given satisfactory results.

Therapeutic monitoring of new antipsychotic drugs

Typical antipsychotic drugs qualify for therapeutic drug monitoring (TDM) primarily for the following reasons: control of compliance and avoidance of extrapyramidal side effects by keeping chronic exposure to minimal effective blood levels. For the atypical antipsychotic clozapine, drug safety is another reason to use TDM. With regard to the new antipsychotics risperidone, olanzapine, quetiapine, amisulpride, ziprasidone, and aripiprazole, which have been introduced in the clinic during the last few years, the rationale to use TDM is a matter of debate. Positron emission tomography (PET), which enables measurement of the occupancy of dopamine D2 receptors, revealed that receptor occupancy correlated better with plasma concentrations than with doses of the antipsychotics. Regarding plasma levels related to therapeutic effects, optimal concentrations have been established for clozapine (350-600 ng/mL), risperidone (20-60 ng/mL), and olanzapine (20-80 ng/mL) but not for the other new antipsychotics. Studies that included analyses of drug levels in blood reported mean concentrations of 68 ng/mL for quetiapine and 317 ng/mL for amisulpride under therapeutic doses of the antipsychotic drugs. For ziprasidone or aripriprazole, data on therapeutic drug concentrations are so far lacking. In conclusion, evidence is growing that TDM may improve efficacy and safety in patients treated with the new antipsychotic drugs, especially when patients do not respond or develop side effects under therapeutic doses. The few reported investigations, however, need to be confirmed and extended.

Quality control of commercial tablets containing the novel antipsychotic quetiapine

Quetiapine (bis [2-(2-[4-(dibenzo[b,f][1,4]thiazepin-11-yl]ethoxy)ethanol]fumarate) is the most recent agent introduced on the drug market for the treatment of psychotic disorders. Two different analytical methods for the quality control of quetiapine in commercial formulations have been developed and compared: a spectrophotometric method and a capillary zone electrophoretic (CZE) method. The spectrophotometric assay was carried out measuring the absorbance at a wavelength of 246 nm. The CZE method used an uncoated fused-silica capillary and a pH 2.5, 50 mM phosphate buffer as the background electrolyte. The detection wavelength was 205 nm, the separation voltage was 15 kV, and a complete electrophoretic run lasts less than 2.5 min. Extraction of quetiapine from the commercial tablets consisted of a simple one-step treatment with a pH 2.5, 50 mM phosphate buffer. Linearity was observed in the 5-25 microg ml(-1) concentration range of quetiapine for the spectrophotometric method, and in the 5-50 microg ml(-1) concentration range for the electrophoretic method. Both methods gave satisfactory results in terms of repeatability and intermediate precision (RSD<1.9%). Also accuracy values were very good for both methods, the recovery being between 98.2 and 100.5%.

HPLC analysis of the novel antipsychotic drug quetiapine in human plasma

A precise and feasible high-performance liquid chromatographic (HPLC) method for the analysis of the novel antipsychotic drug quetiapine in plasma has been developed. The analysis was carried out on a C8 (150x4.6 mm i.d., 5 micrometer) reversed-phase column, using a mixture of acetonitrile, methanol and pH 1.9 phosphate buffer as the mobile phase; triprolidine was used as the internal standard. Careful pretreatment of the biological samples was implemented by means of solid-phase extraction (SPE). A good linearity was found in the 4-400 ng ml(-1) quetiapine plasma concentration range. The application to some plasma samples of patients treated with Seroquel(R) tablets gave satisfactory results. The accuracy was good (quetiapine mean recovery=92%), as well as the precision (mean RSD=3.3%). The method seems to be suitable for the clinical monitoring of patients treated with quetiapine.