Comparative study of β-cyclodextrin, γ-cyclodextrin and 4-tert-butylcalix[8]arene ionophores as electroactive materials for the construction of new sensors for trazodone based on host-guest recognition

BACKGROUND

Trazodone (TRZ) is a second-generation non-tricyclic antidepressant derived from a triazolopyridine derivative, which is mainly used to treat emotional disorders and conditions related to depressive disorders.

PURPOSE

This study investigated the design, development and characteristics of polyvinyl chloride (PVC) membrane sensors for trazodone HCl (TRZ).

METHODS

The developed sensing membranes were constructed using β-cyclodextrin (β-CD; sensor 1), γ-cyclodextrin (γ-CD; sensor 2) or 4-tert-butylcalix[8]arene (t-BC8; sensor 3) ionophores as sensing materials in addition to ionic sites and dioctyl phthalate in the PVC matrix.

RESULTS

Sensors 1, 2 and 3 displayed fast, stable and near-Nernstian response over a relatively wide trazodone concentration range (7.0×10-6-1×10-3, 5.0×10-5-1×10-3and 8.0×10-6-1.0×10-3 M, respectively), with detection limits of 2.2×10-6, 1.5×10-5 and 2.42×10-6 M, respectively in the pH range of 3.0-6.0. The sensors demonstrated good selectivity for TRZ in the presence of different ionic compounds. The accuracy and precision of the proposed sensors were assessed by the determination of 40.7 μg/ml of TRZ, which showed average recoveries of 99.6%, 99.1% and 98.5% with mean relative standard deviations of 2.4%, 2.5% and 2.6% for sensor 1, 2 and 3 respectively. Molecular modeling was used to calculate the host-guest binding energy. The lowest free binding energy was -6.243, -5.752 and -5.7105 kcal/mol for 1:1 stoichiometry host-guest complexes of trazodone and β-CD, γ-CD and t-BC8, respectively, which was in-line with a Nernstian response.

CONCLUSION

The investigated methods can be applied for the determination of TRZ in pharmaceutical preparations. The results of investigated dosage-form of TRZ show good agreement with those using the US Pharmacopeia method.

Uptake and metabolism of the antidepressants sertraline, clomipramine, and trazodone in a garden cress (Lepidium sativum) model

Environmental contamination with pharmaceuticals has received growing attention in recent years. Several studies describe the presence of traces of drugs in water bodies and soils and their impacts on nontarget organisms including plants. Due to these facts investigations of the uptake and metabolism of pharmaceuticals in organisms is an emerging research area. The present study demonstrates the analysis of three selected antidepressants (sertraline, clomipramine, and trazodone) as well as metabolites and transformation products in a cress model (Lepidium sativum). Cress was treated with tap water containing 10 mg/L of the parent drugs. Employing an analytical approach based on high performance liquid chromatography coupled with quadrupole time of flight or Orbitrap mass spectrometry in MS and MS² modes, in total 14 substances were identified in the cress extracts. All three parent drugs were taken up by the cress and translocated from the roots to the leaves in specific patterns. In addition to this, eleven metabolite species were identified. They were generated by hydroxylation, demethylation, conjugation with amino acids, or combinations of these mechanisms. Finally, the inclusion of control cultures in the experimental setup allowed for a differentiation of "true" metabolites generated by the cress and transformation products generated by plant-independent mechanisms.

Electro-oxidation and determination of trazodone at multi-walled carbon nanotube-modified glassy carbon electrode

A simple and rapid electrochemical method was developed for the determination of trace-level trazodone, based on the excellent properties of multi-walled carbon nanotubes (MWCNTs). The MWCNT-modified glassy carbon electrode was constructed and the electrochemical behavior of trazodone was investigated in detail. The cyclic voltammetric results indicate that MWCNT-modified glassy carbon electrode can remarkably enhance electrocatalytic activity towards the oxidation of trazodone in neutral solutions. It leads to a considerable improvement of the anodic peak current for trazodone, and allows the development of a highly sensitive voltammetric sensor for the determination of trazodone. Trazodone could effectively accumulate at this electrode and produce two anodic peaks at about 0.73 V and 1.00 V. The electrocatalytic behavior was further exploited as a sensitive detection scheme for the trazodone determination by differential-pulse voltammetry. Under optimized conditions, the concentration range and detection limit are 0.2-10 microM and 24 nM, respectively for trazodone. The proposed method was successfully applied to trazodone determination in pharmaceutical samples. The analytical performance of this sensor has been evaluated for detection of analyte in urine as a real sample.

Utility of 7,7,8,8-tetracyanoquinodimethane charge transfer reagent for the spectrophotometric determination of trazodone, amineptine and amitriptyline hydrochlorides

A simple and rapid spectrophotometric method has been developed for the determination of tricyclic anti-depressant drugs such as trazodone (TZH), amineptine (APH) and amitriptyline (ATPH) hydrochlorides in pure form and in different pharmaceutical preparations. The charge transfer (CT) reaction between TZH, APH and ATPH as electron donors and TCNQ as electron acceptor was utilized for their spectrophotometric determination. The optimum experimental conditions, like time, temperature, stoichiometry, solvents, for the CT complex formation are established. The method permits the determination of TZH, APH and ATPH over a concentration range of 10-400, 10-440 and 10-300 microg ml(-1), respectively. The sensitivity (S) is found to be 0.09, 0.087 and 0.069 g cm(-2) for TZH, APH and ATPH, respectively. The SD values are found to be 0.146-0.293, 0.154-0.285 and 0.091-0.212 and RSD values are 0.142-1.92, 0.297-1.92 and 0.212-0.915 for TZH, APH and ATPH, respectively. The low values of the relative standard deviation indicate the high accuracy and precision of the method. The mean recovery values obtained together with a high correlation coefficient values, amount in the range 98-101.5, 98.7-102.9 and 93-101.9 for TZH, APH and ATPH, respectively. The method is applicable for the assay of the investigated drugs in different dosage forms and the results are in good agreement with those obtained by the official method.

Determination of trazodone in urine and pharmaceuticals using micellar liquid chromatography with fluorescence detection

A simple and reliable liquid chromatographic procedure is described for the determination of trazodone in pharmaceutical formulations and urine samples. The optimized procedure uses fluorimetric detection, a C18 column and a micellar mobile phase of sodium dodecyl sulfate (SDS) and 1-butanol. The mobile phase selected for use was 0.2M SDS and 8% 1-butanol fixed at pH 3 with phosphate buffer. The total analysis time was 10 min. For the analysis of urine samples, one great advantage of the method is that no extraction step is required. The quantification limit was 9.5 ng mL(-1), ensuring the analysis of the drug in biological fluids. The procedure shows good accuracy, repeatability and selectivity. Repeatability and intermediate precision were tested for several concentrations of the drug. Good claim percentages were obtained in the analysis of pharmaceutical formulations. Calibration repeatability in urine matrix was also studied in the 0.06-22.4 microg mL(-1) range. Good recoveries were obtained from spiked urine samples. No interferences from common additives frequently administered with trazodone or from endogenous compounds in urine samples were found. The results show that the procedure is suitable for routine analysis of the drug.

Suicide by Multidrug Ingestion

A fatal suicidal ingestion of drugs, together with activated charcoal, is reported. The death occurred 31 hours after the self-administration. The autopsy revealed a large amount of gastric content that appeared to be a compact mass of black color. Toxicologic analyses showed the presence of toxic levels of desalkylflurazepam and trazodone; metamizole and pridinol were also detected. The obtained results supported the hypothesis of a death due to acute intoxication delayed by the self-administration of activated charcoal, which elimination was probably hindered by the action of pridinol.

Sensitive extractive spectrophotometric methods for the determination of trazodone hydrochloride in pharmaceutical formulations

Two simple, rapid and sensitive extractive spectrophotometric methods have been developed for the assay of trazodone hydrochloride (TRH) in pure and pharmaceutical formulations. These methods are based on the formation of chloroform soluble ion-association complexes of TRH with bromothymol blue (BTB) and with bromocresol purple (BCP) in KCl-HCl buffer of pH 2.0 (for BTB) and in NaOAc-AcOH buffer of pH of 3.6 (for BCP) with absorption maximum at 423 nm and at 408 nm for BTB and BCP, respectively. Reaction conditions were optimized to obtain the maximum color intensity. The absorbance was found to increase linearly with increase in concentration of TRH, which was corroborated by the calculated correlation coefficient values (0.9996, 0.9945). The systems obeyed Beer's law in the range of 0.2-14.5 and 0.2-14.1 microg/ml for BTB and BCP, respectively. Various analytical parameters have been evaluated and the results have been validated by statistical data. No interference was observed from common excipients present in pharmaceutical formulations. The proposed methods are simple, accurate and suitable for quality control applications.

Optimization of dansyl derivatization and chromatographic conditions in the determination of neuroactive amino acids of biological samples

BACKGROUND

Amino acid neurotransmitters represent a major class of compounds that are involved in neuronal communication at CNS synapses.

METHODS

Twelve amino acids were separated after precolumn derivatization with dansyl chloride. The biologically important amino acids, taurine, aspartate, glutamate, glycine, alanine and gamma-aminobutyric acid were determined in rat brain tissue and rabbit plasma.

RESULTS

The major modifications to previous methods included isocratic elution instead of gradient elution to reduce time and cost of serial analyses; optimization of mobile phase to improve the separation of free dansyl with derivatives, so as to elide complex steps for the clean of the chromatogram; and selection of an internal standard (Trazodone) to improve the reproducibility and the reliability of procedures. Twelve amino acids were assayed within 35 min. Other alpha-amino acids that are relevant to the make-up of mammalian proteins did not interfere with the determination. The standard curve, recovery, analytical precision and detection limits for each neuroactive amino acid were determined.

CONCLUSION

This assay separated 12 amino acids in a single run. Six neuroactive amino acids were also simultaneous measured by isocratic HPLC with UV detection. The method is applicable in determination of Tau, Glu, Asp, Gly, Ala and GABA in biological samples.

Rapid and sensitive LC/MS/MS analysis of the novel tyrosine kinase inhibitor ZD6474 in mouse plasma and tissues

ZD6474 (N-(4-Bromo-2-fluorophenyl)-6-methoxy-7-[(1-methylpiperidin-4-yl)methoxy] quinazolin-4-amine) is a tyrosine kinase inhibitor with anti-angiogenic and anti-tumor activity that is currently undergoing human trials for cancer treatment. Pharmacokinetic studies in animal models are an important component in clinical development of this agent to relate pre-clinical models to patient treatment. A liquid chromatography tandem mass spectrometry method was developed for the determination of ZD6474 levels in mouse plasma and tissues. Plasma (0.05 mL) and tissue homogenates (0.1 mL of 10 mg/mL) were extracted under alkaline conditions with ethyl acetate:pentane (1:1, v/v) after addition of the internal standard (trazodone, 2-[3-[4-(3-chlorophenyl)-1-piperazinyl]propyl]-1,2,4-triazolo[4,3-a]pyridine-3(2H)-one). Separation was achieved on a C18, 50 mm x 2 mm column with quantitation by internal standard reference and multiple reaction monitoring of the ion transitions m/z 475-->112 (ZD6474) and m/z 372-->176 (trazodone). The calibration curve was linear from a range spanning 20-20,000 ng/mL in plasma and 10-320 ng/mg in tissue homogenates. Mean recoveries from plasma and tissue homogenates were 88 and 90%, respectively. The accuracy in plasma was 88% at the lower limit of quantitation (20 ng/mL with a 50 microL plasma sample) with high precision (R.S.D.%<10%). Assay performance in liver and other tissue homogenates is also reported. The assay was applied to a pharmacokinetic study in mice to determine dosing schedules that would approximate therapeutic ZD6474 levels determined in humans.

An automated approach to salt selection for new unique trazodone salts

PURPOSE

The purpose of this study was to establish an automated approach to salt selection and to search for unique trazodone salts for new applications.

METHODS

Automated procedures were developed on a Biomek 2000 automation workstation with stacker and plate reader capabilities. Trazodone was dispensed into 96-well plates, and an automated method was set up to form 104 trazodone salts. Salts were observed under a polarized light microscope to determine crystallinity. After stepwise eliminations, the remaining salts were scaled-up and subjected to differential scanning calorimetry (DSC), powder x-ray diffraction (PXRD), hygroscopic, pH-solubility, density, surface area, and particle size analyses.

RESULTS

Oils formed in several cases resulting in preliminary elimination of mesyl and esyl salts and four crystallizing solvents. Crystallinity was observed in 34 of 44 scaled-up trazodone salts. PXRD, DSC, and hygroscopic analyses indicated a number of new salts that were comparable in physicochemical parameters to the marketed HCl salt. Among them, the tosylate salt showed uniqueness for new applications.

CONCLUSIONS

Automated procedures can be developed to increase the efficiency of pharmaceutical salt selection. The new tosylate salt gave a unique pH-solubility profile with low solubility over the entire pH range making it a potential candidate for a suspension or prolonged action formulation.

New colorimetric methods for the determination of trazodone HCl, famotidine, and diltiazem HCl in their pharmaceutical dosage forms

Two sensitive and simple spectrophotometric methods are developed for the determination of trazodone HCl, famotidine, and diltiazem HCl in pure and pharmaceutical preparations. The methods are based on the oxidation of the cited drugs with iron(III) in acidic medium. The liberated iron(II) reacts with 1,10-phenanthroline (method A) and the ferroin complex is colorimetrically measured at 510 nm against reagent blank. Method B is based on the reaction of the liberated Fe(II) with 2,2-bipyridyl to form a stable colored complex with lambda(max )at 520 nm. Optimization of the experimental conditions was described. Beer's law was obeyed in the concentration range of 1-5, 2-12, and 12-32 microg mL(-1) for trazodone, famotidine, and diltiazem with method A, and 1-10 and 8-16 microg mL(-1) for trazodone and famotidine with method B. The apparent molar absorptivity for method A is 1.06x10(5), 2.9x10(4), 1.2x10(4) and for method B is 9.4x10(4 )and 1.6x10(4), respectively. The suggested procedures could be used for the determination of trazodone, famotidine, and diltiazem, both in pure and dosage forms without interference from common excipients.

Electroanalytical characteristics of piribedil and its differential pulse and square wave voltammetric determination in pharmaceuticals and human serum

The electrochemical oxidative behavior of piribedil (PR) was described. It was investigated by cyclic, linear sweep, differential pulse (DPV) and square wave (SWV) voltammetric techniques. The redox behavior of PR was found irreversible. Different parameters were tested to optimize the conditions for the determination of PR. The dependence of intensities of currents and potential on pH, concentration, scan rate, nature of the buffer was investigated. Two sensitive methods for the measurement of PR were described. For analytical purposes, a very well resolved diffusion controlled voltammetric peak was obtained in 0.1 M H(2)SO(4) and pH 5.7 acetate buffer. The determination peaks are obtained at 1.27 and 0.95 V for differential pulse and 1.29 and 0.97 V for SWV in 0.1 M H(2)SO(4) and pH 5.7 acetate buffer, respectively. The linear response was obtained in the ranges of 2 x 10(-6)-1 x 10(-3) M in 0.1 M H(2)SO(4) and 2 x 10(-6)-8 x 10(-4) M in pH 5.7 acetate buffer for both techniques. The proposed techniques were successfully applied to the determination of PR in tablet dosage forms and human serum. Excipients did not interfere in the determination. The necessary statistical validation reveals that the proposed methods are free from significant systematic errors.

Voltammetric analysis of trazodone HCl in pharmaceuticals and biological fluids

The voltammetric behavior of trazodone (TRZ) HCl was studied using direct current (DC(t)), differential pulse (DPP) and alternating current (AC(t)) polarography. The drug manifests cathodic waves over the pH range of 10-14. The waves were characterized as being irreversible, diffusion-controlled with limited adsorption properties. At pH 10, the diffusion current-concentration relationship was found to be rectilinear over the range 4-32 and 0.8-24 microg ml(-1) using DC(t) and DPP modes, respectively, with minimum detectability (S/N=2) of 0.104 microg ml(-1) (2.45 x 10(-6) M) and 0.314 microg ml(-1) (7.397 x 10(-6) M) using the DPP and DC(t) modes, respectively. The diffusion-current constant (I(d)) is 4.31+/-0.02 (n=6). The proposed method was successfully applied to the determination of the studied compound either in pure form or in formulations. The results obtained were favorably compared with those given using a reference method. Furthermore, the proposed method was applied to the determination of TRZ in spiked human urine and plasma adopting the DPP technique. No prior extraction step is needed in case of urine. The percentage recoveries were 98.43+/-0.79 and 97.44+/-0.705 (n=4) in spiked human urine and plasma, respectively. A pathway for the electrode reaction was postulated.

AAS and AES determination of furaltadone, methadone and trazodone in pharmaceutical formulations

Ion-associate complexes of furaltadone, methadone and trazodone hydrochlorides with [Cd(SCN)(4)](2-) and [Zn(SCN)(4)](2-) were precipitated and the excess unreacted cadmium or zinc complex was determined. A new method using atomic emission and atomic absorption spectrometry for the determination of the above drugs in pure solutions and in pharmaceutical preparations is given. The drugs can be determined by the affort method in the ranges 7.2-72.16, 6.9-69.18 and 8.1-81.6 microg/ml solutions of the three drugs, respectively.

Postmortem forensic toxicology of trazodone

Trazodone is a popular antidepressant medication that has been available for approximately 30 years. It has a reputation as a safe drug with relatively few reported fatalities attributed solely to it. We review the pharmacology and forensic toxicology of trazodone and report toxicology and cause and manner of death in a series of 37 deaths in which trazodone was detected. Although the normal upper therapeutic blood concentration for trazodone is about 2 mg/L, fatalities are rarely attributed solely to it at blood concentrations below 9 mg/L. Considering the pharmacology of the drug, potential interactions between other drugs with serotonin reuptake properties need to be considered, as does the increased susceptibility to the toxic effects in patients with pre-existing heart disease. In the cases reviewed, none were attributed solely to trazodone, although trazodone was frequently present together with other serotonergic drugs, such as the selective serotonin reuptake inhibitors like fluoxetine and sertraline. Ten cases had blood trazodone concentrations above 2 mg/L. Of these cases, trazodone played a primary role in the death of three subjects, with blood concentrations all greater than 9 mg/L. We confirm the conclusions of others that trazodone is a relatively safe drug except in massive overdose, although its toxicity may be influenced by the presence of other drugs and underlying pathophysiology.

Pharmacokinetic and pharmacodynamic analyses of trazodone in rat striatum by in vivo microdialysis

The aim of this study was to investigate the brain pharmacokinetics and pharmacodynamics of trazodone. Sensitive microbore high-performance liquid chromatographic methods with electrochemical detection (LC-ED) were developed for the determination of trazodone, serotonin (5-HT), and their respective metabolites. The feasibility of microdialysis coupled with LC-ED system for direct analysis of these compounds in the rat striatum was investigated. Striatal dialysates were automatically injected onto a cyano microbore column, through an on-line injector, for the determination of trazodone and its metabolite or onto a reversed phase microbore column for the determination of 5-HT and its metabolite. A monophase phenomenon with a first-order elimination rate constant was observed for trazodone. The brain pharmacokinetics of trazodone appear to conform to a one-compartment model. Surprisingly, no significant changes in striatal 5-HT or its metabolite were observed following the same dosage and time course. The present results suggest that brain microdialysis methods may be applicable to pharmacokinetic and pharmacodynamic studies of psychotrophic agents.

Ion-selective electrode for the determination of trazodone in tablets

A coated wire trazodone-selective electrode based on incorporation of trazodone-tetraphenylborate ion pair in a poly(vinylchloride) coating membrane was constructed. The influences of membrane composition, temperature, pH of the test solution, and foreign ions on the electrode performance were investigated. The electrode showed a Nernstian response over a trazodone concentration range from 1.41 x 10(-5) to 0.89 x 10(-2) M, at 25 degrees C, and was found to be very selective, precise, and usable within the pH range 2.4-9.0. The standard electrode potentials, E degree, were determined at 20, 25, 30, 35, 40 and 45 degrees C and used to calculate the isothermal temperature coefficient (dE degree/dT) of the electrode. Temperatures higher than 45 degrees C seriously affected the electrode performance. The electrode was successfully used for potentiometric determination of trazodone hydrochloride both in pure solutions and in pharmaceutical preparations.

Voltammetry of trazodone by platinum electrode and its determination in tablets using DP technique in the rotating conditions

The voltammetric behaviors of trazodone using a platinum electrode in stationary or rotating conditions and its determination in tablets by DP rotating electrodes are described in this study. The experiments were conducted in the supporting electrolyte consisting of 0.2 M KCl and 0.2 M acetate or phosphate buffer. No adsorption was observed at +300 mV. The factor affecting the voltammetric current was diffusional in the range of 200-2000 rpm for rotating, and 2-10 mV potential rate for stationary conditions; and the calibration dependence was linear between 1x10-5-5x10-5 M trazodone solutions. The detection limit was found to be 2.5x10-6 M (sb=5.03, n=5) for stationary and 1.7x10-6 M (sb=2.12, n=5) for rotating electode assuming a signal to noise ratio of 3. According to the statistical evaluations, acceptable results were obtained at the 95% probability level. Therefore, the proposed method is practicable, sensitive and accurate for the analysis of trazodone preparations in quality control laboratories.

Potential of high-performance liquid chromatography with photodiode array detection in forensic toxicology

The potentials and limitations of high-performance liquid chromatography-photodiode array detection are highlighted in respect to its use in the analysis of different biological matrices followed by the identification of unknowns. The logical analytical approach used in clinical and forensic toxicology, vital for the identification of one or more toxic substances as a cause of intoxication, is largely based on both simple and fast "general unknown screening" methods which cover most relevant drugs and potentially hazardous chemicals. In this field of systematic toxicological analysis, a literature overview shows that HPLC can play a substantial role. Both column packing material and eluent composition have their impact on intra- and interlaboratory reproducibility. In view of the sometimes different retention characteristics of various HPLC columns, several possibilities are addressed to enhance the discriminating power of primary retention parameters. The advantages of photodiode array detection as compared to UV detection have been of paramount importance to the success of HPLC in toxicological analysis. Dedicated libraries with spectral information and searching software are powerful tools in the process of identification of an unknown substance. In the present paper, these aspects are also verified in a number of real cases, i.e., trazodone and dothiepin, azide, chloroquine and cocaine, in which we illustrate from our own experience the potentials of HPLC-photodiode array detection in systematic toxicological analysis.

Drug accumulation and elimination in Calliphora vicina larvae

Calliphora vicina larvae were fed on drug-laden muscle from three suicides involving amitriptyline, temazepam and a combination of trazodone and trimipramine; triplicate daily harvestings were analysed. The limit of detection for all four drugs was 0.01 micrograms drug/g larvae. Mean drug concentrations (microgram/g) in the initial muscle were:amitriptyline, 2.68; temazepam, 4.04; trazodone, 21.56; and trimipramine, 19.58. Larval rearings for days 4-8 (15 larval samples per drug) had mean and ranges of drug concentrations (microgram/g) of 0.10 (r, 0.02-0.24) for amitriptyline; 0.52 (r, 0.26-0.78) for temazepam; 0.13 (r, 0.05-0.32) for trazodone; and 0.28 (r, 0.10-0.59) for trimipramine. After day 8 there was a precipitous fall in larval drug concentrations associated with pupariation. At day 11 ranges of drug concentrations (microgram/g) were: amitriptyline, < 0.01-0.01; temazepam, 0.01-0.08; trazodone, < 0.01-0.01; and trimipramine, 0.04-0.04. Day 16 pupae had corresponding ranges (microgram/g) of < 0.01, 0.01-0.01, < 0.01 and < 0.01-0.02. Transfer to drug-free food at day 5 led to similar falls in drug concentrations (microgram/g) from day 5 to day 6: 0.08-0.03 for amitriptyline, 0.61-0.09 for temazepam, 0.13-0.01 for trazodone, and 0.30-0.02 for trimipramine. The results show considerable variation in larval drug concentrations, both at the same developmental stage and at different stages of the life cycle, under conditions which closely reflect case situations. In practice, the precipitous decrease in drug concentrations in non-feeding larvae and at pupariation make it desirable to sample only larvae actively feeding on a corpse.

A widely applicable electrode sensitive to basic drugs based on poly(vinyl chloride) membrane plasticized with tricresyl phosphate

A plastic membrane ion-selective electrode applicable to many basic drugs has been developed. The electrode developed was constructed with tricresyl phosphate and a poly(vinyl chloride) matrix on a polytetrafluoroethylene film. The electrode showed a near-Nernstian response to chlorpromazine, trihexyphenidyl, imipramine, dibucaine, papaverine, propranolol, tetracaine, trazodone, quinidine and cinnarizine. The determination of 50 to 3000 micrograms/ml of trazodone hydrochloride in a pH 4.0 acetate buffer solution showed an average recovery of 99.4% (mean standard deviation 0.7%) by direct potentiometry. Inorganic cations and pharmaceutical excipients did not interfere with the determination. Trazodone hydrochloride and trihexyphenidyl hydrochloride in tablets were determined, and the results compared favorably with those obtained by conventional methods.

Measurement of trazodone in plasma and brain of rat by capillary gas chromatography with a nitrogen-selective detector

A specific and highly sensitive method for the measurement of trazodone in plasma and brain of rat is presented. The compound and the internal standard were extracted from alkalinized samples with hexane and analysed by capillary gas chromatography with nitrogen-selective detection. The method was demonstrated to be accurate and precise. The limits of determination were 2 ng/ml for plasma and 24 ng/g for brain, which makes this procedure suitable for pharmacokinetic analysis.

High-performance liquid chromatographic assay with ultraviolet detection for the determination of etoperidone and two active metabolites, 5-(1-hydroxyethyl) etoperidone and 1-(3-chlorophenyl)piperazine, in plasma

A selective and sensitive high-performance liquid chromatographic assay with ultraviolet detection for the determination of the antidepressant drug etoperidone and two active metabolites in plasma is described. The drug, metabolites and internal standard are isolated from plasma using a two-step liquid-liquid extraction procedure. The resulting sample is chromatographed on a C18 column (10 cm x 2.1 mm I.D.) with ultraviolet detection at 254 nm. Standard curves are linear for each compound over the concentration range 2-1000 ng/ml. The accuracy and precision of the assay, expressed as the percentage deviation of measured values from the true value and the relative standard deviation (inter-run), are less than or equal to 10% at all concentrations except the minimum quantification limit. Using an automated injector and computerized data acquisition, eighty samples can be routinely processed in one day. The assay has been successfully used for the analysis of plasma samples from pharmacokinetic studies in mice, rats, dogs and humans.

Quantitative analysis of trazodone hydrochloride in tablets by an ion-selective electrode

A simple assay procedure for the quantitation of trazodone hydrochloride in tablets, without prior separation, has been developed using a trazodone-selective electrode. The electrode was based on a trazodone:tetrakis(p-chlorophenyl)borate ion-pair complex, dioctyl phthalate, and polyvinyl chloride matrix that were mounted on a PTFE membrane. The electrode showed a near-Nernstian response in the range of 10(-2) to 5 x 10(-6) M trazodone over the pH range of 2.5 to 5.0, with a cationic slope of 58 mV/concentration decade. The durability of the electrode and the reproducibility of the performance among the electrodes were sufficient. The electrode was used for the determination of the pKa value of trazodone. The selectivity of the electrode to a number of interferences was investigated. Many inorganic cations (alkali and alkaline earth metals) and pharmaceutical excipients did not interfere, but some organic ammonium compounds interfered according to their extractability. Determination of 10 to 3000 micrograms/mL of trazodone hydrochloride in aqueous solution showed an average recovery of 100.6% (mean standard deviation 0.4%) by direct potentiometry. This assay was applied to determine trazodone hydrochloride in tablets and the results compared favorably with those obtained by high-performance liquid chromatography.

Measurement of trazodone using solid-phase extraction and wide-bore capillary gas chromatography with nitrogen-selective detection

A method for the determination of the antidepressant drug trazodone is presented. 8-Hydroxyloxapine is used as the internal standard. A simple solid-phase extraction procedure utilizing disposable reversed-phase C18 columns is described. Samples are analyzed by gas chromatography with nitrogen-selective detection using a wide-bore capillary column with a permanently bonded, nonpolar stationary phase. The assay possesses linearity to 3.0 micrograms/mL, sensitivity to at least 0.25 microgram/mL, recovery averaging 96%, and between-run precision reflected by a CV of 5.6%. We conclude that the method reported here is ideally suited for monitoring therapeutic and toxic levels of trazodone.

Determination of trazodone and its metabolite, m-CPP, in serum and urine by HPLC

A sensitive and rapid method for the analysis of trazodone (TZD) and its metabolite, 1-(m-chlorophenyl)piperazine (m-CPP), in the serum and urine of rabbits treated with the drug was developed. The assay requires extraction from the biological fluids with adequately buffered organic solvents followed by HPLC. The assay allows good reproducibility, fair recovery, and excellent linearity in the range of 0.6 to 10 micrograms/mL for TZD and 1.2 to 20 micrograms/mL for m-CPP.

The capillary gas chromatographic determination of trazodone in biological specimens

A simple and specific method is presented for the capillary gas chromatographic determination of trazodone in postmortem blood and tissues. The drug and trimethobenzamide, which was used as an internal standard, were extracted with 1% isopropanol in n-butyl chloride. Chromatography was accomplished with a short (4-m) methyl silicone capillary column and hydrogen carrier gas. This combination of extraction solvent and chromatographic conditions was demonstrated to be both accurate and precise. Since trazodone is a relatively new drug, additional thin layer and packed column gas chromatographic data is presented to augment the incorporation of trazodone into routine analytical protocols.

Trazodone--a new assay procedure and some pharmacokinetic parameters

1 A simple and specific procedure is described for the determination of the new anti-depressant trazodone in human plasma utilising reverse-phase HPLC which is sensitive to 20 ng ml-1. 2 Following oral administration of single 50 mg doses of two formulations of trazodone on separate occasions to healthy fasted volunteers, the peak plasma concentration, time to peak concentration, area under the curve, elimination rate constant and half-life were determined. 3 The two formulations are closely similar and they are considered to have comparable bioavailability.