J. L. Lastres

Preparation and Characterization of Albendazole β-Cyclodextrin Complexes

Albendazole (ABZ), mebendazole (MBZ), and ricobendazole (RBZ) are low-soluble anthelmintic benzimidazole carbamate drugs. To increase their aqueous solubility, three different types of β-cyclodextrins (CyDs): β-cyclodextrin (CD), hydroxypropyl-β-cyclodextrin (HPCD), and methyl-β-cyclodextrin (MCD) were used. Solubility depended on the type of CyDs. Increased solubility was obtained when the more substituted CyDs (HPCD or MCD) were used instead of nonsubstituted CD. Stability constants were calculated assuming a 1:1 stoichiometry. Calculated stability constant values depended on initial solubility of drug and pH of the medium. Solid ABZ complexes were prepared by coprecipitation and freeze-drying methods. These products were compared with physical mixtures of ABZ and CyDs. The characterization of these products was made by differential scanning calorimetry (DSC) and drug release studies. True inclusion complexes were obtained only by the freeze-drying method. Drug release studies showed that the freeze-dri...

Comparison of derivative spectrophotometric and liquid chromatograpic methods for the determination of omeprazole in aqueous solutions during stability studies

A first derivative spectrophotometric method was developed for the determination of omeprazole in aqueous solutions during stability studies. The derivative procedure was based on the linear relationship between the omeprazole concentration and the first derivative amplitude at 313 nm. The first derivative spectra was developed between 200 and 400 nm (deltalambda = 8). This method was validated and compared with the official high-performance liquid chromatography (HPLC) method of the USP. It showed good linearity in the range of concentrations studied (10-30 microg ml(-1)), precision (repeatability and inter-day reproducibility), recovery and specificity in stability studies. It also seemed to be 2.59 times more sensitive than the HPLC method. These results allowed to consider this procedure as useful for the rapid analysis of omeprazole in stability studies since there was no interference with its decomposition products.

Micromeritic and Packing Properties of Diclofenac Pellets and Effects of Some Formulation Variables

The effects of two common diluents (microcrystalline cellulose and calcium phosphate dihydrate), two binding agents (gelatin and methacrylic polymer), and spheronization on the micromeritic (size, shape, density), flow, and packing properties of sodium diclofenac pellets were examined. The shape was assessed as the aspect ratio and was correlated to the flow rate and to the deviation of the tapped porosity from the value of 26%, which corresponds to the ideal rhombohedral packing of spheres. It was found that porosity deviation decreased greatly with spheronization, but it increased with binder addition. Porosity deviation was proportional to the aspect ratio, while flow rate decreased logarithmically with porosity deviation. Porosity deviation may be a useful index for monitoring the quality of pellets, similar to the aspect ratio, as a successful, simple, and indirect indication of sphericity and of surface roughness as well.

First-derivative spectrophotometric and LC determination of nifedipine in Brij® 96 based oil/water/oil multiple microemulsions on stability studies

A first-derivative spectrophotometric (1D(387)) method was developed for the determination of nifedipine in oil/water/oil (O/W/O) multiple microemulsions during stability studies. The UV first-derivative spectra were recorded over the wavelength range 200-600 nm (Delta lambda=16). The derivative procedure was based on the linear relationship between nifedipine concentration and the first-derivative amplitude at 387 nm. This method was validated and compared with a liquid chromatography (LC) procedure used for the quantitative analysis of the drug. Both methods showed excellent precision and accuracy with values of 2.09 and 1.82%, respectively, for the LC method and of 1.53 and 1.64%, respectively, for the 1D(387) method. The established linearity range was 5-30 microg ml(-1) with r(2) values of 0.9980 and 0.9988 for LC and first-derivative procedures, respectively. Nifedipine recoveries from spiked placebos were >95% for both methods over the linear range analysed. These methods have been successfully used for determining of nifedipine content of multiple microemulsions during stability studies, since there was no interference with its decomposition products.

Matrix Tablets Containing HPMC and Polyamide 12: Comparison of Dissolution Data Using the Gompertz Function

There have been several studies reported which have evaluated the controlled drug release from hydrophillic (1,2) or hydrophobic (3) polymeric matrix tablets, but the Y do not show anything about mixed matrices containing the two kinds of polymeric materials. In a previous paper, we have studied the in vitro dissolution data from mixed matrix tablets containing HPMC and polyamide 12, by means of an analysis of variance of parameters which do not require any model hypothesis. Now the effect on the dissolution profiles of different ratios of the hydrophillic polymer and the hydrophobic one, is evaluated by a mathematical model

Comparison of UV spectrophotometric and LC methods for the determination of nortriptyline hydrochloride in polysorbate 80 based oil/water (o/w) microemulsions

A new rapid, reliable and specific UV spectrophotometric method was developed for the determination of nortriptyline hydrochloride formulated into o/w microemulsions. The UV spectra of nortriptyline standard solution in methanol and placebo (microemulsion without nortriptyline) were recorded over the wavelength range 200-600 nm and the spectra for placebo and nortriptyline loaded microemulsion were recorded over the range 260-400 nm in order to determine the overlapping that might appears, and hence to set the wavelength that could be used for the quantitative analysis. This method was validated and compared with a liquid chromatography (LC) procedure used for the quantitative analysis of the drug. Both methods showed excellent precision and accuracy with RSD values of 2.37 and 1.41%, respectively, for the LC method, and values of 1.24 and 2.88%, respectively, for the UV spectrophotometric method. The established linearity range was 10-50 microg ml(-1) (r2 = 0.9985) and 20-60 microg ml(-1) (r2 = 0.9979) for the HPLC and UV spectrophotometric methods respectively. The recoveries of nortriptyline from spiked placebos were > 95% for both methods over the linear range. The methods have been successfully used for determining the nortriptyline content of microemulsions and for evaluating the chemical stability of the drug in nortriptyline-loaded microemulsions.

Liquid Chromatographic Determination of Methylparaben and Propylparaben in Nortriptyline Hydrochloride Oil-Water Microemulsions

SummaryA reversed-phase LC method using UV detection has been developed and validated for the analysis of methylparaben and propylparaben in nortriptyline hydrochloride oil-water (o-w) microemulsions. The precision and accuracy of the method was excellent with RSD values of 4.53% and 2.13% respectively for methylparaben, and 3.69% and 2.06% respectively for propylparaben. The linearity established was 50–150% of theoretical concentrations of each product in dosage form, withr2 0.9940 for methylparaben and 0.9956 for propylparaben. Recoveries of all products from spiked placebos were >95%, with detection limits 0.86 µg · mL−1 for methylparaben, and 0.06 µg · mL−1 for propylparaben. The method was successfully used for determining both compounds in nortriptyline o-w microemulsions.

Extraction and LC determination of lysine clonixinate salt in water/oil microemulsions

A new reversed-phase high performance liquid chromatography method has been developed and validated for the quantitative determination of lysine clonixinate salt in water/oil microemulsions. The mobile phase was acetonitrile-buffer phosphate pH 3.3. Detection was UV absorbance at 252 nm. The precision and accurately of the method were excellent. The established linearity range was 5-60 microg ml(-1) (r(2)=0.999). Microemulsions samples were dispersed with chloroform and extracted lysine clonixinate salt with water. This easy method employing chloroformic extraction has been done three times. The recovery of lysine clonixinate salt from spiked placebo and microemulsion were >90% over the linear range.