Effect of compressional forces on piroxicam polymorphs

Nanovesicle Formulation Enhances Anti-inflammatory Property and Safe Use of Piroxicam

BACKGROUND

Enhanced utilization of certain drugs may be possible through the development of alternative delivery forms. It has been observed that NSAIDs have adverse gastrointestinal tract effects such as irritation and ulceration during anti-inflammatory therapy. This challenge may be overcome through nano topical formulations.

OBJECTIVE

This study aimed to explore the potentials of a transdermal nanovesicular formulation for safe and enhanced delivery of piroxicam (PRX), a poorly water-soluble NSAID.

METHODS

Preformulation studies were conducted using DSC and FTIR. Ethosomal nanovesicular carrier (ENVC) was prepared by thin-film deposition technique using Phospholipon® 90 H (P90H) and ethanol and then converted into gel form. The formulation was characterized using a commercial PRX gel as control. Permeation studies were conducted using rat skin and Franz diffusion cell. Samples were assayed spectrophotometrically, and the obtained data was analyzed by ANOVA using GraphPad Prism software.

RESULTS

The preformulation studies showed compatibility between PRX and P90H. Spherical vesicles of mean size 343.1 ± 5.9 nm, and polydispersity index 0.510 were produced, which remained stable for over 2 years. The optimized formulation (PE30) exhibited pseudoplastic flow, indicating good consistency. The rate of permeation increased with time in the following order: PE30 > Commercial, with significant difference (p< 0.05). It also showed higher inhibition of inflammation (71.92 ± 9.67%) than the reference (64.12 ± 7.92%).

CONCLUSION

ENVC gel of PRX was formulated. It showed potentials for enhanced transdermal delivery and anti-inflammatory activity relative to the reference. This may be further developed as a safe alternative to the oral form.

Characterization of two polymorphs of lornoxicam

Objectives

The aim of the study was to prepare and to characterize two polymorphs of lornoxicam, a water-insoluble non-steroidal anti-inflammatory drug, which has thus far received no exploration of its polymorphs.

Methods

Form I and form II of lornoxicam were prepared by recrystallization and characterized by X-ray powder diffractometry (XRPD), thermal analysis, Fourier transform infrared spectroscopy and scanning electron microscopy. The solubility and dissolution of both polymorphs were also determined and compared to provide the basis for polymorph selection in formulation.

Key findings

The crystal structures of the two polymorphs were established by the experimental XRPD patterns. Form I was demonstrated to be triclinic with two kinds of intermolecular hydrogen bonds, while form II was orthorhombic with two kinds of intramolecular hydrogen bonds. The morphologies of form I and form II were observed to be rectangle and approximately oval, respectively.

Conclusions

Form II had the significantly higher solubility and dissolution and would be the suitable polymorph for the preparation of oral and injectable dosage forms of lornoxicam.

Statistical analysis of differences in the Raman spectra of polymorphs

Raman spectroscopy is a useful tool for identifying polymorphs of pharmaceutical compounds. One limitation of the technique is that the small differences in Raman spectra require confirmation of polymorphs by other methods. Fourteen compounds, both commercial and proprietary pharmaceutical compounds and their polymorphs, were analyzed by Raman microscopy. By using descriptive statistics and analysis of variance (ANOVA), several methods are proposed that provide an approach for comparing the spectra of suspected polymorphs. Because it is difficult to determine the exact amount that a peak may shift before two forms should be considered different; a guideline of a shift greater than 1.6/cm(-1) is proposed. A standard ANOVA analysis is used to compare individual peaks both within and between polymorphs, as well as an alternative method that proposes the use of a total ANOVA table that considers the entire spectrum. Both methods have their advantages and disadvantages, but they provide a starting point for the comparison of a large number of spectra, and effectively differentiate between polymorphs of a given compound. The method accurately identified true polymorphs in all cases, but showed a bias towards misidentifying some samples as polymorphs when they were in fact the same form. This bias was not significant and even in these situations, the magnitude of the calculated F values was a useful indicator of whether the result was a false positive or not.

Crystal forms of tolbutamide from acetonitrile and 1-octanol: effect of solvent, humidity and compression pressure

The possibility of obtaining tolbutamide polymorphs was investigated using the solvents acetonitrile and 1-octanol. Tolbutamide is an oral hypoglycemic agent that exists in four polymorphic forms. Characterization of the various polymorphs was carried out by differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), infrared spectroscopy (FTIR), optical microscopy and dissolution studies. Form A, crystallized from acetonitrile, resembled the form I polymorph, while form O, crystallized from 1-octanol, resembled the form III polymorph. Tablets of both form A and form O were produced at compression pressures of 2500 lbs and 5000 lbs using cornstarch and talc and were exposed to 40%, 75% and 95% RH conditions. DSC and PXRD studies did not show any significant drug-excipient interaction. Moreover, the change in the crystalline state of either form upon exposure to humidity was not evident. Dissolution studies showed a significantly lower drug release rate from form O tablets compressed at 5000 lbs pressure and exposed to 95% RH. Pressure and humidity had no significant effect on the dissolution profiles on the form A tablets. It was concluded that form A was the robust choice for further formulation development.

“Soft Tableting”: A New Concept to Tablet Pressure Sensitive Materials

The aim of this study was to confirm the hypothesis that tableting using excipients with greater elastic deformation results in improved performance of pressure-sensitive drugs relative to the excipients with low elastic deformation. Tableting with highly elastic deforming excipients and the resultant minimization of the process damage is referred to in this article as "soft tableting." Carrageenans, chitosans, and polyethylene oxides were tested as potentially useful tableting excipients. alpha-Amylase, amorphous indomethacin, theophylline monohydrate, and enteric-coated pellets were used as models for pressure-sensitive materials. Three-dimensional modeling of the tableting data and elastic recovery of the tablets were the tools for mechanical characterization. The crushing force of the tablets was analyzed. Inactivation of alpha-amylase was determined by using the starch iodine reaction method. Pseudopolymorphic and polymorphic changes were analyzed using Fourier transform (FT) Raman spectroscopy. The effects of pressure on the integrity of the pellets were tested by release studies and scanning electron microscopy. The process of tablet formation was characterized for potentially useful tableting excipients. The results were compared with the results of traditional excipients as microcrystalline cellulose (MCC), dicalcium phosphate dihydrate, and hydroxypropyl methylcellulose (HPMC). A ranking order for soft tableting was deduced from the mechanical properties. The tableting excipients were ranked according to their general plasticity (GP): GP(carrageenans)<GP(chitosans)<GP(MCC)<GP(HPMC)<GP(polyethylene oxides). This theoretical order of suitability has been experimentally proven to be valid for the pressure-sensitive materials. In conclusion, the new concept for soft tableting is valid.

Potential of carrageenans to protect drugs from polymorphic transformation

Carrageenans were analysed in mixture with polymorphic drugs to test their potential for minimising polymorphic or pseudopolymorphic transitions, which are induced by the tableting process. The kappa-carrageenans Gelcarin GP-812 NF and Gelcarin GP-911 NF and the iota-carrageenan Gelcarin GP-379 NF were tested in comparison to the well-known tableting excipients microcrystalline cellulose (MCC), hydroxypropyl methylcellulose (HPMC), and dicalcium phosphate dihydrate (DCPD). Amorphous indomethacin was chosen as model drug since its well-known recrystallisation behaviour can be mechanically stimulated. Further on, theophylline monohydrate was used. Its dehydration is induced by tableting. Pure materials and mixtures containing 20% (w/w) drug were compressed up to different maximum relative densities. The data obtained during tableting were analysed by three-dimensional (3D) modelling. Afterwards tablets were broken and examined by Fourier transform Raman spectroscopy in order to determine the degree of transformation inside the tablet. For quantitative interpretation, the intensities of representative bands were used. Thermal analysis was used additionally. Using 3D modelling a decrease of plastic deformation can be noticed in the order HPMC>MCC>carrageenans, whereas DCPD represents an exception because of brittle fracture. Best hindrance of polymorphic transformation showed the carrageenans, the hindrance was slightly worse for HPMC. MCC and DCPD could not hinder transformation. A complete protection of the amorphous form could not be achieved. For theophylline monohydrate, the results were similar.

Characterization of piroxicam crystal modifications

Piroxicam polymorphism was extensively studied in the past. The objective of the present work was to evaluate polymorphism of piroxicam once again and to characterize the obtained crystal forms. Three polymorphic forms and one monohydrate form were obtained by crystallization from saturated solutions in various solvents. Polarity of solvents and crystallization rate defined by temperature of crystallization were found to be critical parameters in determining the polymorphic form. A new polymorphic form designated as form III was obtained by forced crystallization using dry ice. Only form I with the highest melting point was found to be stable under mechanical and thermal stress. Differences in IR spectra were attributed mainly to the differences in number and positions of H-bonds in the piroxicam crystal forms. Slow crystallization of piroxicam from absolute ethanol solution resulted in a mixture of form II and monohydrate. Crystal structure analysis proved that form II represents form alpha(2) already proposed in the literature. Differences in dissolution rates among crystal forms of piroxicam were attributed to differences in their wettability, where highest wettability was obtained for monohydrate and the lowest for form III.

Improved dissolution behaviour of steam-granulated piroxicam

In this paper we prepared and characterized improved release granulates containing Piroxicam and beta-cyclodextrins (1:2.5 molar ratio), obtained by steam-aided granulation, using a one-step rotogranulator, Rotolab. These granulates were compared to those prepared by traditional wet granulation, to the physical mixture, and to the kneaded and dry granulates. The experimental data showed a significant reduction of the water amount required (50%) and of the working time, with respect to traditional wet granulation. The samples examined by scanning electron microscopy and fractal analysis revealed morphological differences related to the method of preparation: the steam-granulated material showed a diffuse porosity, as confirmed by the porosity test. Differential scanning calorimetry, infrared and X-ray analysis revealed the absence of polymorphs in the solid state of the drug. The results of the dissolution tests suggest that the steam-aided granulation may be considered a useful method to improve the in vitro dissolution rate of Piroxicam, enabling also a considerable reduction in the processing time.

The use of solution calorimetry with micellar solvent systems for the detection of polymorphism

The presence of multiple polymorphic forms in seven batches of raw material of a model compound having poor wettability properties (cimetidine) was studied by solution calorimetry. Due to the large number of polymorphic forms described in the literature ('Gazz. Chim. Ital., 109 (1979) 535'; 'J. Pharm. Sci., 73 (1983) 1436'; 'J. Pharm. Biomed. Anal., 3 (1985) 303') and its poor wettability characteristics, cimetidine was chosen as a model compound to illustrate the possible use of solution calorimetry in the detection of polymorphism using surfactant systems as solvents for dissolution. Due to the closeness of the melting points of the different polymorphic forms of cimetidine, DSC was not the best investigational tool. As initially suspected, the measurement of enthalpy of solution values in water of the cimetidine batches was not possible. However, the use of sodium dodecyl sulfate (SDS) and polysorbate 20 (Tween 20(R)) at concentrations above their respective cmc values permitted the detection of significant differences in enthalpy of solution among several batches. The presence of different polymorphic forms was confirmed by microscopy, X-ray powder diffractometry, and Fourier transform infrared spectroscopy.