Validated spectrophotometric and spectrofluorimetric methods for determination of dapoxetine hydrochloride and dosulepin hydrochloride in their dosage forms using mercurochrome.

Validated, simple, rapid and sensitive spectrophotometric and spectrofluorimetric methods were developed for the determination of dapoxetine HCl and dosulepin HCl. The spectrophotometric method (I) was based on a binary complex formation between each drug and mercurochrome (MER) in acetate buffer (pH 3.5) with maximum absorbance at 557 nm. Calibration graphs were linear over the range 2.0-20.0 and 2.0-24.0 µg/ml, detection limits were 0.23 and 0.41 µg/ml and quantitation limits were 0.71 and 1.26 µg/ml for dapoxetine HCl and dosulepin HCl, respectively. Spectrofluorimetric method (II) was based on the measurement of the quantitative quenching effect of each drug on the native fluorescence of MER at the same pH. Fluorescence quenching of MER was measured at 538 nm after excitation at 470 nm. Calibration graphs were linear over the range 0.5-10.0 and 0.4-10.0 µg/ml, detection limits were 0.17 and 0.12 µg/ml and quantitation limits were 0.5 and 0.36 µg/ml for dapoxetine HCl and dosulepin HCl, respectively. Statistical comparison of results with those obtained by reported methods provided good agreement and revealed that there were no significant differences in accuracy and precision between methods. The proposed methods were applied successfully to analyse commercial tablets and capsules containing the studied drugs.

Extractive colorimetric method for the determination of dothiepin hydrochloride and risperidone in pure and in dosage forms.

Three rapid, simple, reproducible and sensitive extractive colorimetric methods (A--C) for assaying dothiepin hydrochloride (I) and risperidone (II) in bulk sample and in dosage forms were investigated. Methods A and B are based on the formation of an ion pair complexes with methyl orange (A) and orange G (B), whereas method C depends on ternary complex formation between cobalt thiocyanate and the studied drug I or II. The optimum reaction conditions were investigated and it was observed the calibration curves resulting from the measurements of absorbance concentration relations of the extracted complexes were linear over the concentration range 0.1--12 microg ml(-1) for method A, 0.5--11 mug ml(-1) for method B, and 3.2--80 microg ml(-1) for method C with a relative standard deviation (RSD) of 1.17 and 1.28 for drug I and II, respectively. The molar absorptivity, Sandell sensitivity, Ringbom optimum concentration ranges, and detection and quantification limits for all complexes were calculated and evaluated at maximum wavelengths of 423, 498, and 625 nm, using methods A, B, and C, respectively. The interference from excipients commonly present in dosage forms and common degradation products was studied. The proposed methods are highly specific for the determination of drugs I and II, in their dosage forms applying the standard additions technique without any interference from common excipients. The proposed methods have been compared statistically to the reference methods and found to be simple, accurate (t-test) and reproducible (F-value).

Spectrophotometric and spectrofluorimetric methods for analysis of tramadol, acebutolol and dothiepin in pharmaceutical preparations.

Sensitive spectrophotometric and spectrofluorimetric methods are described for the determination of tramadol, acebutolol and dothiepin (dosulepin) hydrochlorides. The two methods are based on the condensation of the cited drugs with the mixed anhydrides of malonic and acetic acids at 60 degrees C for 25-40 min. The coloured condensation products are suitable for the spectrophotometric and spectrofluorimetric determination at 329-333 and 431-434 nm (excitation at 389 nm), respectively. For the spectrophotometric method, Beer's law was obeyed from 0.5 to 2.5 microg ml(-1) for tramadol, dothiepin and 5-25 microg ml(-1) for acebutolol. Using the spectrofluorimetric method linearity ranged from 0.25 to 1.25 microg ml(-1) for tramadol, dothiepin and 1-5 microg ml(-1) for acebutolol. Mean percentage recoveries for the spectrophotometric method were 99.68+/-1.00, 99.95+/-1.11 and 99.72+/-1.01 for tramadol, acebutolol and dothiepin, respectively and for the spectrofluorimetric method, recoveries were 99.5+/-0.844, 100.32+/-0.969 and 99.82+/-1.15 for the three drugs, respectively. The optimum experimental parameters for the reaction has been studied. The validity of the described procedures was assessed. Statistical analysis of the results has been carried out revealing high accuracy and good precision. The proposed methods were successfully applied for the determination of the selected drugs in their pharmaceutical preparations with good recoveries. The procedures were accurate, simple and suitable for quality control application.

Polymeric membrane electrodes for selective determination of methiaden.

Polyvinyl chloride matrix membrane ion-selective electrodes for the determination of methiaden hydrochloride based on the ion-pair of methiaden cation with tetraphenylborate anion were prepared using bis(2-ethylhexyl)sebacate, (electrode A), 2-nitrophenyl octyl ether (electrode B). 2-nitrophenyl dodecyl ether (electrode C) and 1-isopropyl-4-nitrobenzene (electrode D) as the membrane solvents. The electrodes exhibit near-Nernstian response in different concentration ranges, depending on the used membrane solvents. The basic analytical parameters of these electrodes were evaluated. The potentiometric titration method was used to determine methiaden hydrochloride with good precision and accuracy.

Kinetic spectrophotometric methods for the determination of dothiepin hydrochloride in bulk and in drug formulation.

Two simple and sensitive kinetic methods for the determination of dothiepin hydrochloride are described. The first method is based on kinetic investigation of the oxidation reaction of the drug with alkaline potassium permanganate at room temperature for a fixed time of 25 min. The absorbance of the colored manganate ions is measured at 610 nm. The second method is based on the reaction of dothiepin hydrochloride with 4-chloro-7-nitrobenzofurazan (NBD-Cl) in the presence of 0.1 mol L(-1) sodium bicarbonate. Spectrophotometric measurement was achieved by recording the absorbance at 470 nm for a fixed time of 60 min. All variables affecting the development of the color were investigated and the conditions were optimized. Plots of absorbance against concentration in both procedures were rectilinear over the ranges 4-24 and 50-250 microg mL(-1), with mean recoveries 99.33+/-0.42 and 99.88+/-0.53, respectively. The proposed methods were successfully applied for the determination of dothiepin hydrochloride in bulk powder and in capsule dosage form. The results obtained were found to agree statistically with those given by the non-aqueous B.P. method. Furthermore the methods were validated according to USP guidelines and also assessed by applying the standard addition technique. The determination of dothiepin hydrochloride by the fixed concentration method is feasible with the calibration equations obtained, but the fixed time method proves to be more applicable.

Fatal intoxication due to dothiepin.

An ingestion of an unknown quantity of Harmomed (dothiepin and diazepam) capsules in a suicide is described. The authors report a new and fast method of analysing and determining the dothiepin concentration in postmortem specimens. Quantitation of dothiepin, and its metabolite desmethyldothiepin was performed by ethyl acetate extraction from alkalinized body fluids before GC-MS analysis. The analyses were performed without any complex sample clean-up steps and with little sample material. Postmortem concentrations of dothiepin, desmethyldothiepin, diazepam and desmethyldiazepam in body fluids are given. The proposed method is a rapid procedure for analysis in cases of deliberate poisoning with the antidepressant drug dothiepin.

Drug concentration in selected skeletal muscles.

We evaluated the homogeneity of drug concentrations in muscle in 14 cadavers, comprising 11 drug overdoses and three cases of chronic therapeutic drug use. Analyses were performed on samples from twelve named muscles and femoral venous blood. Standard analytical techniques and instrumentation were used throughout. There was marked within-case variability in drug concentrations with highest:lowest concentrations ranging up to 21.7. Overall highest concentrations were found in the diaphragm and mean diaphragm:blood ratios ranged from 1.1 (temazepam, two cases) and 1.2/1.3 (paracetamol, six cases) up to 6.5/13.5 (amitriptyline, three cases) and 5.3/21.3 (propoxyphene, four cases). Excluding the diaphragm, mean muscle:blood ratios ranged from 0.4 (prothiaden), 0.5 (temazepam), and 0.7 (paracetamol) up to 3.7 (temazepam), 4.3 (propoxyphene) and 5.7 (amitriptyline). We suggest that muscle is suitable for qualitative analysis but not for quantitative corroboration of a blood sample or as a quantitative alternative to blood.

Site-to-site variability of drug concentrations in skeletal muscle.

The homogeneity of drug concentrations in skeletal muscle was assessed in eight fatal overdoses. Ten to 30 random samples were taken from leg muscle weighing 1,650 to 7,985 g. For cases involving paracetamol the mean muscle-to-blood ratio ranged from 0.1 to 1.1 (n = 4) for amitriptyline 1.1 to 3.6 (n = 3), and for dothiepin 0.8 to 2.1 (n = 2). The coefficient of variance was large for all drugs, ranging from 10.5 (carbamazepine) to 50 (thioridazine). Skeletal muscle is not homogeneous with respect to drug concentrations in fatal overdose cases. Of 16 instances of drug detection in blood 2 (nortriptyline and promethazine) were not detected in muscle. Muscle-to-blood drug ratios varied significantly among cases, possibly influenced by survival time after drug ingestion. Quantitative interpretations of muscle drug levels present significant difficulties. However, skeletal muscle can be used for qualitative corroboration of blood analyses and is a suitable specimen for drug detection where none other is available.

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.

A fatal dothiepin overdose.

High pressure liquid chromatography coupled to photodiode array detector and capillary gas chromatography coupled to mass spectrometry were employed to quantify dothiepin in biological fluids, tissues and hair in a death attributed to oral dothiepin (Prothiaden) ingestion. The blood concentration of dothiepin was 5.75 mg/l. Hair analysis clearly indicated a chronic antidepressant exposure, with a dothiepin concentration of 1.89 ng/mg hair. Results are discussed in the light of the existing literature.

The determination of the geometric isomers and related impurities of dothiepin in a pharmaceutical preparation by capillary electrophoresis.

The application of capillary zone electrophoresis in the assay of the tricyclic antidepressant drug, dothiepin, in tablets is discussed. The method developed for dothiepin which exists as the cis- and trans-isomers and contains two major related impurities, an 11-oxo compound and a propanamine, utilizes inclusion complexation with beta-cyclodextrin. For optimization of the method the structured procedure of factorial design was used; the electrolyte solution was 50 mM disodium hydrogen phosphate with 10 mM beta-cyclodextrin-propan-1-ol(90:10, v/v). Good precision (RSD = 1.06%, n = 6), linearity (y = 26.84x + 2.25), and correlation (r = 0.999, n = 7) was obtained for trans-dothiepin. The reproducibility of tablet extraction was also acceptable (RSD = 0.77%, n = 6); the recovery of the trans-isomer was 98% (w/w) and the level of cis-isomer in tablets of dothiepin (75 mg) was 5.58% (w/w).

Determination of dosulepin and its metabolite: application of high-performance liquid chromatography with electrochemical detection.

Dosulepin, 11-(3-dimethylaminopropylidene)-6,11-dihydrodibenzo [b,e]thiepin hydrochloride, is a thio analogue of amitriptyline and is used for the treatment of anxiety and affective disorders. The present study developed a simple and sensitive procedure for the determination of this compound and its metabolite, northiaden, by a combination of high-performance liquid chromatography with electrochemical detection. Hydrodynamic voltammograms demonstrated an optimal applied potential at 1300 mV for both dosulepin and northiaden. A mobile phase consisting of 0.1 M acetate buffer-acetonitrile-perchloric acid-trichloroacetic acid (50:50:2:1.5) provided the best separation of the drugs. The extraction procedure, which used a heptane-isoamyl alcohol (99:1) mixture, was successfully applied with a recovery of over 90%. A preliminary pharmacokinetic study was performed by the proposed method.