Chemometric quality inspection control of pyrantel pamoate, febantel and praziquantel in veterinary tablets by mid infrared spectroscopy

This paper describes the development and validation of a new multivariate calibration method based on diffuse reflectance mid infrared spectroscopy for direct and simultaneous determination of three veterinary pharmaceutical drugs, pyrantel pamoate, praziquantel and febantel, in commercial tablets. The best synergy interval partial least squares (siPLS) model was obtained by selecting three spectral regions, 3715-3150, 2865-2583, and 2298-1733 cm(-1), preprocessed by first derivative and Savitzky-Golay smoothing followed by mean centering. This model was built with five latent variables and provided root mean square errors of prediction (RMSEP) equal or lower than 0.69 mg per 100 mg of powder for the three analytes. The method was validated according the appropriate regulations through the estimate of figures of merit, such as trueness, precision, linearity, analytical sensitivity, bias and residual prediction deviation (RPD). Then, it was applied to three different veterinary pharmaceutical formulations found in the Brazilian market, in a situation of multi-product calibration, since the excipient composition of these commercial products, which was not known a priori, was modeled by an experimental design that scanned the likely content range of the possible constituents. The results were verified with high performance liquid chromatography with diode array detection (HPLC-DAD) and high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) and were in agreement with the predicted values at 95% confidence level. The developed method presented the advantages of being simple, rapid, solvent free, and about ten times faster than the HPLC ones.

Determination of active substances in binary mixture antiparasitic veterinary formulations by HPLC

The purpose of the study was to develop a simple, versatile HPLC method for the identification and quantification of praziquantel and ivermectin (in Equimax) or praziquantel and abamectin (in Abamitel Plus). A satisfactory separation was obtained using the Supelcosil LC-ABZ+ column in gradient system with a mobile phase A: acetonitrile / water in 40:60 ratio and phase B: acetonitrile. The UV detection was set at 245 nm. The correlation coefficient values (> or = 0,998) for all active substances confirmed that the calibration curves (peak area vs. concentration) are linear. The results of the quantification and the statistical evaluation confirmed that the method is accurate and precise. It can also be applied to confirm the identity of benzyl alcohol, methyl p-hydroxybenzoate and propyl p-hydroxybenzoate in Abamitel Plus formulation.

[Determination of praziquantel residue in aquatic products using high performance liquid chromatography]

A sensitive and simple method for the determination of praziquantel residue in aquatic products has been established. The sample was extracted with ethyl acetate for three times (20 mL, 20 mL, 10 mL) and cleaned up with an LC-Si column. The extract was separated on a ZORBAX SB-C18 column (250 mm x 4.6 mm, 5 microm). Ultraviolet detection was performed at 214 nm. Acetonitrile-water (50: 50, v/v) was used as the mobile phase at a flow rate of 0.9 mL/min. The calibration curve of praziquantel in aquatic products at the concentration range of 0.02 - 20 mg/L was linear ( r = 0.999 98). The recovery of praziquantel was higher than 85%. The limit of detection was 10 microg/kg (S/N > 3).

A high-performance liquid chromatography and nuclear magnetic resonance spectroscopy-based analysis of commercially available praziquantel tablets

The amount of active ingredient in 20 commercially sourced batches of praziquantel (PZQ) tablets was determined using a high-performance liquid chromatography-ultraviolet (HPLC-UV) assay in conjunction with an anthentic, lot of PZQ powder. The general composition of each batch of tablets was also examined by means of (1)H nuclear magnetic resonance (NMR) spectroscopy and the NMR data were subjected to pattern recognition analysis by means of principal component analysis. The HPLC-UV results showed that each batch of PZQ tablets contained approximately the required amount of PZQ (600 mg per tablet). The NMR analysis showed a high degree of compositional variation between manufacturers, which caused by variation in excipients, along with some batch-to-batch variation in the tablets from a single manufacturer. Additionally, the PZQ tablets from one manufacturer were found to have an extra component (methyl-4-hydroxybenzoate) that was not detected in the other preparations.

Bioavailability and pharmacokinetics of a praziquantel bolus in kingfish Seriola lalandi

Oral praziquantel (PZQ) preparations have recently been investigated for the treatment of monogeneans that infect the skin and gills of kingfish Seriola lalandi cultured in sea-cages. To evaluate an oral PZQ dosing strategy, the pharmacokinetics of a dissolved and in feed oral PZQ preparation (40 mg kg(-1) body weight) were compared with an intravenous bolus in kingfish plasma and skin using HPLC. Compared with intravenous administration, PZQ bioavailability (area under curve, AUC0-24h) was slightly improved when the drug was administered with food in both kingfish plasma (56.8% in feed vs. 50.8% in solution) and skin (55.5% in feed vs. 50.3% in solution). After oral dosing, maximum drug concentrations in skin were approximately one-third of those achieved in plasma and higher when the drug was administered in solution (5.26 microg ml(-1)) than in feed (3.96 microg ml(-1)); additionally, the time to achieve maximum PZQ concentration was similar in plasma and skin, although markedly reduced when the drug was administered in solution (1 h) than in feed (6 h). However, clearance of the drug was delayed in skin; administered as an oral formulation, PZQ concentrations in the systemic circulation fell below the limit of quantification after 24 h, but remained quantifiable (0.3 microg g(-1)) in skin at this time. These initial studies indicate that a daily treatment interval will lead to the exposure of parasites to highly variable anthelmintic concentrations, which may be sub-optimal for the treatment of monogeneans in this finfish species.

Investigation of the phase diagrams of chiral praziquantel

In the present work, thermal properties of praziquantel, including melting point phase diagram and solubility, were determined for the purpose of exploration on an integrated enantioseparation process of chromatography and crystallization. The solubility of racemic praziquantel in methanol and 2-propanol was measured in the temperature range between 0 and 40 degrees C. In agreement with previous conclusions, the resulting phase diagram reveals the racemic compound behavior of praziquantel arising from the existence of eutectics. A ternary phase diagram of praziquantel enantiomers and the methanol system was also determined. Based on the information provided by the ternary solubility phase diagram, an optimized integrated enantioseparation process was suggested. Pure praziquantel crystals were recovered, and the crystal structure was solved by X-ray crystallography.

Structural characterization and enantioseparation of the chiral compound praziquantel

In this study, we aimed to characterize the chiral compound type of a leading antischistosomal drug, praziquantel. The optically pure praziquantel enantiomers were recovered from the racemic mixture by enantiomeric separation, which was performed on preparative scale chromatography by using a novel beta-cyclodextrin type chiral column. The thermodynamic properties of praziquantel were determined from differential scanning calorimetry and the physical properties were studied by examining Fourier transform infrared spectroscopy and X-ray powder diffraction. Based on the differential scanning calorimetry data, a melting point binary phase diagram was constructed. A ternary solubility phase diagram of praziquantel in methanol was also determined at the temperature of 0 degrees C. All the experimental results support the conclusion that praziquantel is a racemic compound. The characterization of physical properties of praziquantel and the phase diagram are crucial for understanding the rationality for the successful resolution of praziquantel and also provide the basis for designing the strategy of separation and recovery of pure enantiomer.

Direct determination of praziquantel in pharmaceutical formulations and human plasma by cathodic adsorptive stripping differential-pulse voltammetry

The polarographic and cyclic voltammetric behaviour of praziquantel was studied in B.R. buffers of different pH values. Contradictory to that mentioned in a previously published work, praziquantel is an electro-active compound. Its polarogram exhibited a single 2-electron irreversible reduction wave in B.R. buffer of pH 5, the wave height decreased on the increase of pH till it disappeared in solution of pH >7. This wave was attributed to the reduction of the Cz.dbnd6;O double bond. The quantitative trace determination of bulk praziquantel was studied at a hanging mercury drop electrode by cathodic adsorptive stripping differential-pulse voltammetry. A fully validated sensitive procedure based on controlled adsorptive accumulation of the drug onto a HMDE was developed for its direct determination without derivatization. Accumulation of praziquantel was found to be optimized in 0.1 M Na(2)SO(4) solution as supporting electrolyte under the following conditions: accumulation potential, -1.2 V (vs. Ag/AgCl/KCl(s)); accumulation time, 30 s; scan rate, 10 mV/s and pulse height 100 mV. The proposed procedure was applied successfully for determination of praziquantel in its pharmaceutical formulations and human plasma. The mean recoveries of the drug were 98.85-99.42% and 99.12-100.47% with RSD of 0.49-0.95% and 0.45-0.52% in pharmaceutical formulations and human plasma, respectively. Limits of detection and quantitation of 1.14x10(-9) and 3.80x10(-9) M praziquantel, respectively, were achieved.

Voltammetric determination of praziquantel in tablets and biological fluids

A simple method is described for the determination of praziquantel (CAS 55268-74-1) in its pure form, tablet formulations and biological fluids. The proposed method depends upon the polarographic activity of praziquantel at the dropping mercury electrode (DME) in Britton Robinson buffers, whereby a well-defined catholic wave is produced over the pH range 7-12. The wave was characterized as being irreversible diffusion-controlled with limited adsorption properties. The diffusion current constant (Id) was 0.56 +/- 0.004 (n = 11). The current-concentration relationship was found to be rectilinear over the range 8-48, 3.2-38.4 and 0.48-20 micrograms.ml-1 using direct current (DCt), differential pulse polarographic (DPP) and alternating current (ACt) odes, respectively, with minimum detection limit (S/N = 2) of 0.32 microgram.ml-1 (1.02 x 10(-6) mol/l and 0.02 microgram.ml-1 (6.4 x 10(-8) mol/l) for DPP and ACt modes respectively. The average percent recovery was favourably compared to a reference method with a satisfactory standard deviation. The proposed method was applied to spiked human urine and plasma. The percentage recoveries were 99.33 +/- 0.79 and 98.23 +/- 0.53, respectively.

Vilsmeier formylation of praziquantel: synthesis and application for polarographic assay

A simple and sensitive method for the polarographic determination of praziquantel (1) after derivatization using Vilsmeier formylation is described. The polarographically active compound obtained by this procedure has been separated, identified and prepared using N,N-dimethylformamide and phosphorus oxychloride.

Sensitive high-performance liquid chromatographic assay for praziquantel in plasma, urine and liver homogenates

A high-performance liquid chromatographic method for the determination of praziquantel in plasma, urine and rat liver homogenates has been developed. It requires 2 ml of biological fluid, an extraction using Sep-Pak cartridges, a 0.05 M phosphate buffer solution (pH 5.0) for equilibrating and washing and ethyl acetate-diisopropyl ether for drug elution. The analysis was performed on an Ultrasphere ODS C18 column with a mobile phase of acetonitrile-water with ultraviolet detection at 217 nm. The results showed that the assay is sensitive (31.2 ng/ml), linear between 0.125 and 4.0 micrograms/ml, precise (coefficient of variation = 10%) and selective with other drugs currently administered with praziquantel.

Colorimetric method for the quantitative determination of the antibilharzial drug praziquantel and its application to pharmaceutical preparations

A method for the colorimetric assay of praziquantel has been developed. For the colorimetric assay, it was necessary to hydrolyse praziquantel with 3 mol dm-3 NaOH, 6 mol dm-3 HCl and 85% phosphoric acid separately. 4-Chloro-7-nitro-2,1,3-benzoxadiazole (NBD-Cl) reacts with the basic hydrolysis product in methanolic aqueous phosphate buffer (pH 7.4), resulting in the formation of an orange product with a characteristic absorption maximum at 478 nm. The red-orange product of the interaction between the hydrochloric acid hydrolysis product and NBD-Cl showed an absorption maximum at 486 nm. The colours obtained were stable for 24 h. The colour system obeyed Beer's law in the concentration range 2-15 and 2-18 micrograms ml-1 for the basic hydrolysis product and the acid hydrolysis product, respectively. The results obtained showed good recoveries with relative standard deviations of 0.378 and 0.47% for the basic and the acid hydrolysis product, respectively. The determination limit was found to be 0.124 and 0.150 micrograms ml-1 for the praziquantel basic hydrolysis product and the acid hydrolysis product, respectively. The coloured reaction products obtained with the proposed method were synthesized. The structures of these products were studied and the compounds identified.

[Determination of praziquantel levels in cerebrospinal fluid and plasma in patients with cysticercosis of the central nervous system treated with praziquantel]

The CSF and plasma concentrations of praziquantel (PZQ) were determined with high pressure liquid chromatography in 37 patients with cysticercosis of the central nervous system during a dosing regimen of PZQ 20 mg/kg p o q 8h for 3 days. The pharmacokinetic parameters were estimated using the nonlinear least squares method. The results showed that PZQ could pass through the blood-brain barrier. The absorption and elimination rates in CSF were slower than those in plasma, the corresponding mean levels being 0.1 and 0.27 micrograms/ml, which were lower than those in plasma. There was a linear correlation between CSF and plasma concentrations (r = 0.87, P less than 0.01). The neurological complications during the period of therapy were not related to the CSF level of PZQ. The cure rates of muscular and cerebral cysticerci were 14/14 and 5/37 respectively. The difference in susceptibility was considered to be caused by the pharmacokinetic behavior of PZQ and CSF and plasma. It was suggested that in general favorable regimens had better be adjusted with adequate increase of the dosage of PZQ, shortening the dosing interval, and prolong the period of PZQ treatment, but individualization of the PZQ dosing regiment would be necessary in accordance with the plasma concentration of the PZQ.

[An evaluation of methods for the quantitative determination of praziquantel as a substance]

Feasibility of quantitative determination of a new helminthicide prasiquantel as a substance by spectral and chemical analytic procedures has been investigated. Chemical methods based on nitrogen measurement in the samples were shown to lack precision which is obligatory for drug analysis. The quantitative analytic procedures based on UV spectrophotometry are of low precision and selectivity. Infrared spectroscopy is the only method of prasiquantel assay that meets the requirements for drug substance measurement.

Quantitative studies on the occurrence of praziquantel in milk and plasma of lactating women

10 healthy lactating women were treated orally with the anthelmintic praziquantel (Biltricide), and the resulting timedependent concentrations of the unchanged substance in plasma and milk were determined simultaneously. 5 of the women ("1st trial") received the single dose of 50 mg/kg; the other 5 women ("2nd trial") were treated three times at 4 hour intervals with 20 mg/kg. During the 1st trial a maximal plasma-concentration of 1.30 mg/l (arithmetic mean) was found. Subsequently the mean plasma-concentration decreased continuously and after 24 h it was only 0.4% of the maximum. During the 2nd trial the highest mean value (1.92 mg/l) was found 10 h after the first administration; after 32 h (24 h after the last administration) the mean value was 0.6% of the maximum mean value. The mean areas under the concentration/time-curves were 5.25 h. mg/l and 13.8 h . mg/l, respectively. The plasma half-life was estimated to be 3 hours. In both trials the concentration/time-curves of the milk corresponded qualitatively to those of the plasma. However, in each person and at each time, the concentration in the milk were essentially lower than those in the plasma. On the average, the plasma-concentrations were four times higher than the milk-concentrations. The mean values of the milk-concentrations increased and decreased correspondingly with those of the plasma-concentrations. At the end of the investigation (24 and 32 h, respectively, from the beginning) they were lower than the limit of determination (4 microgram/l). The mean excretion with the milk of the 10 women was 0.0008% of the given dose. From the comparative concentration/time-course, it could be demonstrated that the milk does not represent a deep department but readily equilibrates with the plasma. Equilibration obviously takes place by passive diffusion and not by active secretion.

Quantitative determination of praziquantel in body fluids by gas liquid chromatography

Praziquantel was determined in body fluids by gas liquid chromatography as follows: A known amount of an internal standard and 0.1 N sodium hydroxide solution was added to the sample to be analyzed. After extraction with methyl acetate/diisopropyl ether = 30/70, the organic extract was evaporated, the residue taken up in methylacetate and an aliquot injected for glc analysis. Separation was accomplished on a OV3 silicon oil phase, and for detection and quantitation, a thermoionic FID sensitized for nitrogen-containing compounds was used. The determination limit in serum is about 0.01 micrograms/ml. The relative standard deviation for serum concentrations of 0.1 micrograms/ml was found to be 4.5%.

A fluorometric method for the determination of praziquantel in blood-plasma and urine

Some physicochemical data of praziquantel which may have analytical relevance are reported. For the quantitative determination praziquantel is extracted from plasma or urine by means of organic solvents and then hydrolyzed in an aqueous alkaline solution. The hydrolyzed product is reacted with dansyl-chloride (5-dimethylaminonaphthalene-sulfonylchloride). The dansylated compound is separated and quantified fluorometrically. The limit of determination is 3 micrograms/l in blood plasma and 30 micrograms/d in urine. For both fluids, the imprecision is approximately 7.5%. The method is suitable for the determination of praziquantel in patients or healthy volunteers treated with therapeutic doses.