Small is Powerful: Demonstration of the Impact of Nanoformed Piroxicam in a Controlled Clinical Study

PURPOSE

New solutions are needed to enable the efficient use of poorly water-soluble drugs. Therefore, we aimed to demonstrate that decreasing particle size with a solution-to-particle method known as nanoforming can improve dissolution and thus bioavailability.

METHODS

Piroxicam, a poorly water-soluble non-steroidal anti-inflammatory drug (NSAID), was used as a model compound. A Quality-by-Design (QbD) approach was used to nanoform piroxicam and a design space was established. The pharmacokinetics of piroxicam nanoparticles were compared to two marketed products in a clinical trial.

RESULTS

Nanoformed tablets showed a 33% increase in exposure during the first hour after dosing (AUC0-1 h) compared with an immediate release tablet and was similar to a fast absorbing tablet incorporating complexation of piroxicam with β-cyclodextrin.

CONCLUSIONS

The results show that nanoforming enabled more rapid absorption in comparison to a typical marketed tablet and indicate that nanoforming is an alternative to complex formulation such as cyclodextrins based products. The study outcomes support the potential of nanoforming for producing fast-acting dosage forms of poorly soluble drugs.

Piroxicam loaded polymer hybrid microspheres based tablets with modified release kinetics: Development, characterization and in vivo evaluation

Piroxicam (PC) is a non-steroidal anti-inflammatory drug characterized by poor aqueous solubility and reported to cause and impart crucial GIT irritation, bleeding, peptic and duodenal ulcer. Engineering of PC loaded microcapsules and its surface modification using different polymers has become the popular approach to address the said issues. The purpose of the study was to develop new PC loaded gastro-protective polymer hybrid microspheres (PHM) with subsequent conversion to tablet dosage form having modified dissolution rate and improved bioavailability. The crystallinity of the PC loaded PHM were established through powder X-ray diffraction. The optimised microspheres, PC-M1 with particle size 32±3.0μm, entrapment efficiency 83.78±2.5% and in vitro drug release 87.1±2.6% were further subjected to tablets development and in vivo evaluation. The in vitro drug release study conducted for PHM at pH media 1.2 and 6.8 demonstrated retarded and enhanced drug release rates (P<0.001) respectively. Both accelerated and real time stability studies confirmed stability of the PC loaded PHM based tablets. A substantial improvement in the drug plasma concentration 12.6±2.36 (P<0.001) was observed for the produced tablets compared to the marketed formulations.

Electrospun Gelatin Nanocontainers for Enhanced Biopharmaceutical Performance of Piroxicam: In Vivo and In Vitro Investigations

BACKGROUND

Piroxicam exhibits low oral bioavailability, due to its meager solubility in water. The intent of this study was to ameliorate the bioavailability of the drug by employing a solubility-enhancing encapsulation technique.

METHODS

Seven samples were formulated with piroxicam and gelatin using both solvent evaporation and electrospraying together. Evaluation of solubility and release rate in water and assessment of bioavailability in rats were carried out in comparison with piroxicam plain drug powder (PPDP). Other in vitro explorations were accomplished using powder X-ray diffraction analysis, differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy, and Fourier-transform infrared spectroscopy.

RESULTS

All piroxicam-loaded gelatinnanocontainers (PLGNs) enhanced solubility and release of the payload in water. In particular, a PLGN formulation consisting of piroxicam and gelatin at a 1:8 (w:w) ratio presented about 600-fold the drug solubility of that shown by PPDP. Moreover, 85.12%±10.96% of the payload was released from this formulation in 10 minutes which was significantly higher than that dissolved from PPDP in 10 minutes (11.81%±5.34%). Drug content, drug loading, and encapsulation efficiency of this formulation were 93.41%±0.56%, 10.45%±0.06%, and 66.74%±6.87%, respectively. The drug loaded in PLGNs existed in the amorphous state, as confirmed by X-ray diffraction and differential scanning-calorimetry analyses, and was more stable when analyzed by thermogravimetric analysis. Moreover, Fourier-transform infrared spectroscopy analysis suggested nonexistence of any piroxicam-gelatin interaction in the formulation. In the scanning electron-microscopy image, PLGNs appeared as round, smooth particles, with particle size of <1,000 nm. Amelioration in bioavailability of piroxicam with the aforementioned PLGN formulation was fourfold that of PPDP.

CONCLUSION

The PLGN formulation fabricated with piroxicam and gelatin at 1:8 (w:w) might be a promising system for enhanced biopharmaceutical performance of the drug.

A rapid analysis of piroxicam in beagle plasma applying evaporation-free liquid-liquid extraction by supercritical fluid chromatography-tandem mass spectrometry

Bioequivalence study is highly prized to piroxicam (PIRO), since its generic products have been widely used worldwide. The present work was undertaken to explore the pharmacokinetic behaviors and bioequivalence of two branded PIRO tablets in beagle dogs using the supercritical fluid chromatography tandem mass spectrometry (SFC-MS/MS) method. Here, a fast evaporation-free liquid-liquid extraction (EF-LLE) method using ethyl acetate was developed for extracting PIRO from beagle dog plasma. To improve the response as well as peaks elution and symmetry of analytes, several key factors were investigated including post-column compensation, stationary phase, mobile phase, column temperature, back pressure and flow rate, and finally the analytes were eluted on an ACQUITY UPC2™ BEH 2-EP column (100 × 3 mm, 1.7 μm) within only 2.5 min in optimal conditions. The performance of the established method was evaluated, good linearity was found over the concentration range of 5-5000 ng/mL (R2 ≥ 0.994) with a lower limit of quantification (LLOQ) of 5 ng/mL. Accuracy of all quality control (QC) samples were between 96.6% and 99.6% with a satisfactory intra and inter-day precision (RSD values < 6.6%). The proposed rapid, sensitive, user-friendly and high throughput method will be an alternative way for PIRO analysis in biological samples.

The Enhancement of Nasal Drug Absorption From Powder Formulations by the Addition of Sodium Carboxymethyl Cellulose

For nasal drug absorption, powder formulations can be expected to provide many advantages. The first aim of this study was to examine drug absorption following nasal administration of powder formulations in rats. Pharmaceutical excipients are typically added to most powder formulations. The second aim was to investigate the change in nasal drug absorption of powder formulations in the presence of sodium carboxymethyl cellulose (CMC-Na). Model drugs used were norfloxacin (NFX), warfarin (WF), and piroxicam (PXC). The absorption from bulk powders is different from that of solutions. The absorption of PXC and WF from powder formulations was enhanced compared to those of the other solutions, while that of NFX, which has a low solubility, was decreased, suggesting that the nasal absorption of many drugs, except poorly soluble drugs, is enhanced when they are administered as powder formulations. CMC-Na enhanced the absorption of NFX and PXC. The presence of CMC-Na slightly decreased the absorption of WF. In vitro transepithelial transport from the powder formulation was not affected by the presence of CMC-Na. Furthermore, the nasal retention of the powder formulation was significantly increased in the presence of CMC-Na. In conclusion, the nasal absorption of many drugs, except those that are poorly soluble, can be increased by administering them as a powder formulation and the nasal absorption of the formulation is enhanced further in the presence of CMC-Na.

A QUALITY BY DESIGN APPROACH: FABRICATION, CHARACTERIZATION AND EVALUATION OF OPTIMIZED TRANSDERMAL THERAPEUTIC SYSTEM FOR ANTIRHEUMATIC LORNOXICAM

Microemulsion was prepared using several concentrations of selected oil (pine oil), surfactant (cre- mophor RH40), co-surfactant (isopropanol) and water to improve bioavailability by increasing solubility and permeability of lomoxicam, which was then incorporated to carbomer 940 gel base to fabricate microemulsion based gel (MEBG) to sustained permeability for transdermal delivery. Initially, the formulations were investi- gated for physicochemical characteristics, i.e., pH, conductivity, viscosity, refractive index, zeta size, poly-dis- persity index and Atomic Force Microscopy. Also, the significance of the components on in vitro permeability was observed to find out optimum microemulsion (ME,) using Box-Behnken-Design (BBD). MEBG was com- pared for in vitro permeation, stability, skin irritation and anti-inflammatory studies using control gel and in vivo bioavailability study with oral tablet. Microemulsions exhibited the physiological pH (5.35-5.99), oil in water nature (139-185 tsiemens/cm), isotropic (1.3390-1.4166), narrow size (62 nm), homogeneity, Newtonian flow (52-160 centipoise) and spherical shape. Predicted values (Q2, flux, lag time) of optimized microemulsions derived from BBD were in reasonable agreement with experimental values. The formulations were stable and non-irritating to the skin. Significant difference was investigated when comparing percent inhibition of edema of MEBG (80%) and control gel (40%) with respect to standard. The MEBG behavior differed significantly from oral tablet formulation in vivo bioavailability. Such BBD based estimation will reduce time and cost in drug designing, delivery and targeting.

Effect of the surfactant on the availability of piroxicam as a poorly hydrosoluble drug from suppositories

The use of surfactants in suppository formulations has been suggested to improve availability of poorly soluble drugs. In the present study, different kinds of surfactants have been investigated to clarify the influence on piroxicam release from suppositories formulated with both lipophilic and hydrophilic bases. Two hydrophilic glucose-derivate surfactants, and a polyoxylglyceride amphiphilic surfactant, all with high HLB values, were investigated for their use in improving drug availability. The two glucose derivate surfactants reduced drug availability from both lipophilic suppositories and hydrophilic formulations, according to longer disintegration times and drug micellization. The more complex surfactant, a lauroyl macrogolglyceride, showed an increase in piroxicam availability from lipophilic suppositories at the higher tested concentrations (15% and 20%). Otherwise, when used in hydrophilic formulations, it was less effective in promoting drug release and even reduced drug availability.

Effect of Uraemia and Anephric State on the Pharmacokinetics of Tenoxicam in the Rat

Renal alterations, uraemia and nephrotic syndrome induced in experimental animals caused a reduction in the plasma albumin concentration of 25 and 30%, respectively. As a result of this decrease, the unbound fraction of tenoxicam in uraemic rats (0·06 ± 0·02) and in anephric rats (0·11 ± 0·08) increased with respect to the control group (0·03±0·004). The induced hypoalbuminaemia did not modify the blood to plasma concentration ratio. Both plasma clearance (CL) and apparent volume of distribution at steady-state (Vdss) rose significantly with the increase in the unbound fraction: (Vdss 55 ±6 mL (control rats); 69 ± 12 mL (uraemic rats); 96 ± 30 mL (anephric rats); CL = 7± 1 mL h−1 (control rats); 12 ± 4 mL h−1 (uraemic rats); 15 ± 7 mL h−1 (anephric rats)). Tenoxicam elimination was found to be restrictive, with an extraction ratio less than 0·1 in the three groups. The induction of nephrotic syndrome was observed to have a significant effect on intrinsic metabolic activity, intrinsic clearance of tenoxicam being reduced by 30% in the anephric rats (161 ± 38 mL h−1) with respect to the values obtained in the control group (228 ± 22 mL h−1).

Enhanced Oral Bioavailability of Piroxicam in Rats by Hyaluronate Microspheres

To enhance the dissolution and oral bioavailability of poorly water soluble piroxicam, the piroxicam-loaded hyaluronic microspheres were prepared with various ratios of piroxicam, sodium hyaluronate and polyethylene glycol 4000 (PEG) using a spray dryer, and their physicochemical properties such as shape, size, drug-loading efficiency and dissolution were investigated. The pharmacokinetic study of piroxicam-loaded hyaluronic micropheres in rats was then performed compared to piroxicam powder. The piroxicam-loaded hyaluronic microspheres, spherical in shape, had the geometric mean diameters of about 1.5 microm and drug loading efficiency of about 90%, irrespective of ratio of piroxicam/sodium hyaluronate/PEG. The hyaluronic microspheres containing PEG gave significantly higher dissolution rates of drug than did piroxicam powder, PEG-based solid dispersion system and hyaluronic microspheres without PEG, suggesting that the hyaluronic microsphere with sodium hyaluronate and PEG was more useful for improving the dissolution rate of poorly water soluble piroxicam. The piroxicam-loaded hyaluronic microcapsule composed of (piroxicam/sodium hyaluronate/PEG; 2: 20: 1) gave about threefold improved dissolution of drug in water for 4 h compared to piroxicam powder. It showed higher plasma concentrations of drug compared to piroxicam powder. It gave significantly higher AUC and faster Tmax of piroxicam than did piroxicam powder. In particular, the AUC of piroxicam from hyaluronic microsphere was about twofold higher than that from piroxicam powder, suggesting that it could enhance the oral bioavailability of piroxicam. Thus, the hyaluronic microsphere developed using spray-drying technique with sodium hyaluronate and PEG was a more effective oral dosage form for poorly water soluble piroxicam.

Prediction of oral clearance fromin vitrometabolic data using recombinant CYPs: Comparison among well-stirred, parallel-tube, distributed and dispersion models

Intrinsic clearances (CLint-HLM-total) for the metabolism of NE-100, metoprolol, clarithromycin (CAM), lornoxicam and tenoxicam were predicted from in vitro data with recombinant cytochorme P450s (CYPs) using relative activity factor (RAF) and then compared with CLint-HLM observed in human liver microsomes (HLM). The predicted CLint-HLM-total correlated well with the observed CLint-HLM in HLM. When oral clearances (CLoral) of low-clearance drugs such as metoprolol, CAM, lornoxicam and tenoxicam were predicted from the in vitro data using four physiological models (well-stirred, parallel tube, distributed and dispersion models), the predicted CLoral corresponded well with the observed CLoralin vivo and were similar among the four models. For a high-clearance drug, the predicted CLoral of NE-100 in extensive CYP2D6 metabolizers (EMs) was substantially different between individual models, although the predicted CLoral in a poor metabolizer of CYP2D6 (PMs) was similar. The CLoral ratio of NE-100 between the EMs and the PMs predicted from the dispersion model, which leads to a reliable prediction for the high-clearance drug, was 48.4, but the ratio decreased depending on the increase of the NE-100 plasma concentration. The results suggest that the CLoral decrease in the EMs is caused by saturation of NE-100 metabolism mediated by CYP2D6 and is based on increases in plasma NE-100 concentrations dependent on the dose of NE-100. The study suggests that the RAF and the in vitro-in vivo scaling approaches are useful for predicting CLoral from in vitro data with recombinant CYPs without using HLM and hepatocytes.

In vitro phonophoresis: effect of ultrasound intensity and mode at high frequency on NSAIDs transport across cellulose and rabbit skin membranes

The objective of this study was to evaluate the effect of intensity, mode, and duration of ultrasound application on the transport of three nonsteroidal anti-inflammatory drugs (NSAIDs) across cellulose membrane and rabbit-skin. Ibuprofen, piroxicam and diclofenac sodium were used as the model drugs. Studies were performed in vitro using a modified Franz diffusion assembly adapted to a therapeutic ultrasound transducer. Ultrasound had a significant and positive effect on the transport of the model NSAIDs across cellulose and rabbit skin membranes. Increasing ultrasound intensity from 0.5 to 3.0 W/cm2 led to a proportional increase in drug transport. Continuous ultrasound mode was more effective in enhancing drug transport than the pulsed mode. Diclofenac sodium had the least flux and permeability coefficient. This was attributed to its comparatively lower pKa value that renders the drug more ionizable in the buffer solution, consequently reducing its selective penetration through the membranes. This study demonstrated the therapeutic potential of ultrasound in transdermal delivery of NSAIDs and the synergistic effect of temperature and ultrasound operational parameters on drug transport.

Liquid chromatography-electrospray lonization tandem mass spectrometric determination of lornoxicam in human plasma

A rapid, sensitive and selective liquid chromatography-electrospray ionization tandem mass spectrometric (LC-ESI-MS/MS) method for the determination of lornoxicam in human plasma was developed. Lornoxicam and isoxicam (internal standard) were extracted from human plasma with ethyl acetate at acidic pH and analyzed on a Sunfire C18 column with the mobile phase of methanol:ammonium formate (10 mM, pH 3.0) (70:30, v/v). The analyte was detected using a mass spectrometer, equipped with electrospray ion source. The instrument was set in the multiple-reaction-monitoring mode. The standard curve was linear (r = 0.9998) over the concentration range of 0.50-500 ng/mL. The coefficient of variation and relative error for intra- and inter-assay at four QC levels were 0.7 to 4.2% and -4.5 to 5.0%, respectively. The recoveries of lornoxicam and isoxicam were 87.8% and 66.5%, respectively. The lower limit of quantification for lornoxicam was 0.50 ng/mL using a 200 pL plasma sample. This method was successfully applied to a pharmacokinetic study of lornoxicam after oral administration of lornoxicam (8 mg) to humans.

Study of feline oral squamous cell carcinoma: potential target for cyclooxygenase inhibitor treatment

Oral squamous cell carcinoma (OSCC) is associated with high morbidity and mortality. A potential target for OSCC treatment is cyclooxygenase-2 (cox-2). Pet cats with naturally occurring OSCC may offer the opportunity to study anticancer activity of cox inhibitors. Cox-2 expression in feline OSCC was determined by immunohistochemistry. High intensity cox-2 immunoreactivity was detected in 6 of 34 (18%) feline OSCC samples. Weak immunoreactivity was noted in 22 OSCCs and in epithelial cells from oral mucosa of clinically normal cats. Pharmacokinetics of a cox inhibitor (piroxicam, 0.3 mg/kg) were studied in carcinoma-bearing cats to confirm a dose for follow-up trials. The average peak serum piroxicam concentration (948 ng/ml, which inhibited cox-2 activity) and serum half-life (15.9 h) were similar to that in normal cats. These results provide information (cox-2 expression as an inclusion criteria, 0.3 mg/kg daily piroxicam) for the design of follow-up trials of cox inhibitor treatment in pet cats with OSCC.

[Microspeciation of amphoteric molecules of unusual acid-base properties]

The phisico-chemical properties of bio- and drug molecules greatly influence their interactions in the body and strongly effect the mechanism of drug action. Among these properties, macroscopic and site-specific protonation constants are of crucial importance. Latter one is the tool to calculate the relative concentration of the various microspecies in the compartments of the body at different pH values, and also, it is the versatile parameter to improve the pharmacokinetic properties of a new molecule in a particular family of drugs. In the present thesis work, the microspeciation of three molecules of great pharmaceutical importance and unusual acid-base properties, were carried out. The microconstants of tenoxicam, the non-steroidal anti-inflammatory drug, were described, introducing a novel deductive method using Hammett constants. For this purpose, a total of 8 tenoxicam and piroxicam derivatives were synthesised. To the best of our knowledge, the log k(N)O microconstant of tenoxicam obtained thus is the lowest enolate basicity value, which, however, can be well explained by the effects of the intramolecular environment. The developed evaluation procedure is suitable for microconstant determination of compounds in other molecule families. Besides, prodrug-type compounds and analogues similar to the structures of selective COX-2 isoenzyme inhibitors were synthesised. The other two molecules studied, the 6-aminopenicillanic acid and 7-cephalosporanic acid, the core molecules of the two most important beta-lactam antibiotic-types were derivatised and investigated by 1D and 2D NMR techniques. The NMR-pH titration on the parent compounds and their ester derivatives, combined with in situ pH-measurements allowed the microspeciation of these easily decomposing molecules. One of the protonation constant of 7-ACA (log kN(O) = 4.12), to the best of our knowledge, is the least non-aromatic basic amino-site among the natural compounds.

Effect of the CYP2C9*3 allele on lornoxicam metabolism

BACKGROUND

We investigated whether the CYP2C9 genotypes would affect lornoxicam metabolism in healthy volunteers.

METHODS

Twelve healthy volunteers who had been genotyped for CYP2C9 gene were selected to participate in our study. After 8 mg lornoxicam was taken, blood samples were drawn from 0 to 36 h. The plasma concentrations of lornoxicam and 5'-hydroxylornoxicam were determined by HPLC method. 5'-hydroxylornoxicam was purified from rabbits'urine by semi-preparative HPLC.

RESULTS

Lornoxicam and 5'-hydroxylornoxicam both exhibit CYP2C9 genotype-dependent pharmacokinetic profiles. The area under the plasma concentration-time curve (AUC) of lornoxicam increased by 60 +/- 9.78% (P <0.05) and the AUC of 5'-hydroxylornoxicam decreased by 65 +/- 11.75% (p <0.001) in heterozygous CYP2C9*1/*3 subjects (n=6) compared with CYP2C9*1/*1 group (n=6). t1/2 value of lornoxicam and 5'-hydroxylornoxicam prolonged by 39 +/- 8.35% and curtailed by 59 +/- 6.83% respectively in CYP2C9*1/*3 subjects. But no significant differences in Tmax of lornoxicam and 5'-hydroxylornoxicam were observed between these 2 genotypes. In addition, for the first time we exploit the purification method for 5'-hydroxylornoxicam from rabbits' urine.

CONCLUSION

The CYP2C9*3 allele significantly affected the metabolism of lornoxicam. The pharmacokinetic parameters of both lornoxicam and 5'-hydroxylornoxicam were significantly different between these 2 genotypes.

Novel lipid-based formulations enhancing the in vitro dissolution and permeability characteristics of a poorly water-soluble model drug, piroxicam

Lipid-based delivery systems are becoming increasingly popular as carriers of drugs due to their ability to overcome barriers to oral absorption. The purpose of this study was to prepare novel lipid-based formulations of a model drug, piroxicam (PXCM), a poorly water-soluble non-steroidal anti-inflammatory drug (NSAID) using 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC) phospholipid alone, and in combination with polyethylene glycol (PEG 4600). Lipid-based drug delivery systems were prepared using conventional methods of preparation and the following aspects were evaluated (1) in vitro dissolution behavior, (2) absorption via Caco-2 cell monolayers and (3) stability of formulations over a 12-month period. In addition, physical characterization studies using differential scanning calorimetry (DSC) were also performed. Formulations of PXCM were prepared using DMPC in the following combinations (A) 1:1 and (B) 2:1 and a mixture of DMPC and PEG 4600 (C) 2:1:1, respectively. Dissolution studies conducted in phosphate buffered saline (PBS, pH 7.4, 37+/-0.5 degrees C) using the USP type II (paddle) dissolution apparatus showed an increase in dissolution rate and extent of the PXCM from all solid dispersion formulations when compared to the control. As such, the rate of drug release was observed to be fastest with formulation (C) showing the greatest increase of over two-fold compared to the control. Release of PXCM from formulations (A) and (B) was intermediate with the latter showing superior dissolution behavior despite containing lower amounts of the carrier lipid than the former. This observation indicates a possible existence of threshold levels for phospholipids carriers beyond which dissolution could be adversely affected. DSC studies further confirmed the dissolution behavior of these formulations demonstrating different levels of amorphous to crystalline nature. Results of HPLC analysis from Caco-2 cell culture studies showed increase in transport of PXCM from all formulations, with formulation (C) showing the maximum increase followed by formulations (B) and (A), when compared to control. The apparent permeability coefficients (Papp) were calculated to be 7.92x10(-6), 9.48x10(-6), 9.2x10(-6) and 5.6x10(-6)cm/s for formulations (A)-(C) and control, respectively. Overall, permeation appeared to improve for all formulations over the control. Stability studies at various temperatures showed all formulations to have good stability for the first 6 months; then a decline in dissolution rates was observed, especially for PEG-based lipid carrier systems, attributed to the increase in crystalline content of the solid dispersions upon storage.

A simple pharmacokinetics subroutine for modeling double peak phenomenon

Double peak absorption has been described with several orally administered drugs. Numerous reasons have been implicated in causing the double peak. DRUG-KNT--a pharmacokinetic software developed previously for fitting one and two compartment kinetics using the iterative curve stripping method--was modified and a revised subroutine was incorporated to solve double-peak models. This subroutine considers the double peak as two hypothetical doses administered with a time gap. The fitting capability of the presented model was verified using four sets of data showing double peak profiles extracted from the literature (piroxicam, ranitidine, phenazopyridine and talinolol). Visual inspection and statistical diagnostics showed that the present algorithm provided adequate curve fit disregarding the mechanism involved in the emergence of the secondary peaks. Statistical diagnostic parameters (RSS, AIC and R2) generally showed good fitness in the plasma profile prediction by this model. It was concluded that the algorithm presented herein provides adequate predicted curves in cases of the double peak phenomenon.

Simultaneous determination of piroxicam, meloxicam and tenoxicam in human plasma by liquid chromatography with tandem mass spectrometry

A rapid, sensitive and selective liquid chromatography-tandem mass spectrometric (LC-MS/MS) method for the determination of piroxicam, meloxicam and tenoxicam in human plasma was developed. Piroxicam, meloxicam, tenoxicam and isoxicam (internal standard) were extracted from human plasma with ethyl acetate at acidic pH and analyzed on a Sunfire column with the mobile phase of methanol:ammonium formate (15 mM, pH 3.0) (60:40, v/v). The analytes were detected using a mass spectrometer, equipped with electrospray ion source. The instrument was set in the multiple-reaction-monitoring (MRM) mode. The standard curve was linear (r=1.000) over the concentration range of 0.50-200 ng/ml. The coefficient of variation (CV) and relative error (RE) for intra- and inter-assay statistics at three QC levels were 1.0-5.4% and -5.9 to 2.8%, respectively. The recoveries of piroxicam, meloxicam and tenoxicam ranged from 78.3 to 87.1%, with that of isoxicam being 59.7%. The lower limit of quantification for piroxicam, meloxicam and tenoxicam was 0.50 ng/ml using a 100 microl plasma sample. This method was successfully applied to a pharmacokinetic study of piroxicam after application of transdermal piroxicam patches to humans.

Multiple dose pharmacokinetics and acute safety of piroxicam and cimetidine in the cat

The purpose of this study was to evaluate the multiple dose pharmacokinetics and acute safety of piroxicam and cimetidine alone and in combination in cats. Seven healthy cats were included in this randomized-crossover study. The cats were assigned to groups designated to receive cimetidine alone (15 mg/kg, p.o., q12 h), piroxicam alone (0.3 mg/kg, p.o., q24 h), and piroxicam combined with cimetidine (both at aforementioned doses). The cats were dosed for 10 days followed by at least a 2-week washout period between trials. Serial blood samples were collected following the first and last doses and analyzed utilizing a high-performance liquid chromatography with mass spectrometry detection (LC/MS) assay. Pharmacokinetic parameters were determined using noncompartmental analysis. Endoscopic evaluation of the gastric mucosa was performed and serum urea nitrogen (SUN), creatinine, alkaline phosphatase (ALP), and alanine transaminase (ALT) activities were evaluated. There were not a clinically relevant difference between the pharmacokinetic parameters of piroxicam administered alone or in combination with cimetidine after either the first or last dose. Gastric ulcers were not observed in any cats although gastric erosions were. The SUN, creatinine, ALP, and ALT activities remained within reference ranges for all cats. It appears that once daily, short-term use of piroxicam alone and in combination with cimetidine in cats is relatively safe based on the parameters evaluated in this study. However, further studies are necessary to determine the long-term gastrointestinal safety of piroxicam.

Influence of genotypes on the pharmacokinetics and pharmacodynamics of piroxicam

OBJECTIVE

Our objective was to evaluate the influence of cytochrome P450 (CYP) 2C9 polymorphisms on the pharmacokinetics and pharmacodynamics of the nonsteroidal anti-inflammatory drug piroxicam.

METHODS

Thirty-five healthy subjects with CYP2C9 genotypes *1/*1 (n=17), *1/*2 (n=9), and *1/*3 (n=9) received a single oral dose of piroxicam (20 mg). Blood samples were collected at various time points up to 240 hours for measurements of the concentrations of piroxicam and thromboxane B2 (TXB2).

RESULTS

Piroxicam's area under the plasma concentration-time curve from time 0 to infinity and oral clearance corrected for body weight were 154+/-37 microg.mL-1.h and 2.0+/-0.5 mL.h-1.kg-1, respectively, in CYP2C9*1/*1 individuals, as compared with 256+/-97 mL.h-1 (P=.002) and 1.3+/- 0.4 mL.h-1.kg-1 (P=.002), respectively, in CYP2C9*1/*2 individuals and 259+/- 95 mL.h-1 (P=.002) and 1.3+/- 0.4 mL.h-1.kg-1 (P=.002), respectively, in CYP2C9*1/*3 individuals. There were no significant differences between CYP2C9*1/*2 and CYP2C 9*1/*3 individuals in these pharmacokinetic parameters (P=.95 for area under the plasma concentration-time curve from time 0 to infinity and P=.94 for oral clearance corrected for body weight). The formation of TXB2, reflecting cyclooxygenase type 1 activity, showed significant differences in the area above the effect-time curves (expressed as percent of baseline TXB2.h) between CYP2C9*1/*1 (10,190 +/- 2632) and either CYP2C9*1/*2 (19,255+/-1,291 [P=.00003]) or CYP2C9*1/*3 (18,241+/- 2397 [P=.00003]). The minimum serum TXB2 concentration, however, did not differ among the different genotypes (P=.32, ANOVA).

CONCLUSION

Piroxicam's oral clearance was impaired and its inhibitory effect on cyclooxygenase 1 activity was increased in CYP2C9*1/*2 or CYP2C9*1/*3 individuals, as compared with CYP2C 9*1 homozygous individuals.

[Impact of cytochrome P450 CYP2C9 variant allele CYP2C9 * 3 on the pharmacokinetics of glibenclamide and lornoxicam in Chinese subjects]

AIM

To investigate the impact of CYP2C9 * 3 on the pharmacokinetics of glibenclamide and lornoxicam.

METHODS

CYP2C9 * 3 was measured in 83 non-related Chinese subjects by PCR-RFLP. The pharmacokinetics of lornoxicam and glibenclamide were investigated in 18 subjects (7 with CYP2C9 * 1/* 3 genotype and 11 with * 1/* 1 genotype). Glibenclamide and lornoxicam in plasma were determined by the sensitive liquid chromatography-tandem mass spectrometry, separately.

RESULTS

After a single oral dose of 2.5 mg glibenclamide, C(max) was (70.0 +/- 11.5) microg x L(-1) in CYP2C9 * 1/ * 3 subjects and (51.9 +/- 12.3) microg x L(-1) in * 1/ *1 subjects. AUC(0-infinity) were (435 +/- 47) vs (287 +/- 95) microg x h x L(-1) (in * 1/ * 3 vs * 1/ *1 subjects), and CL/F were (96 +/- 9.3) vs (160 +/- 51) mL x min(-1), respectively. Statistic analysis results indicated that glibenclamide AUC(0-infinity) was significantly higher (1.5-fold) and subsequently CL/F was significantly lower (40%) in CYP2C9 * 1/ * 3 subjects than those in * 1/ * 1 subjects (P < 0.01). After a single oral dose of 8 mg lornoxicam, C(max) was (1.54 +/- 0.24) mg x L(-1) in CYP2C9 * 1/ * 3 subjects and (1.19 +/- 0.37) mg x L(-1) in * 1/ * 1 subjects. AUC(o-infinity were (14.9 +/- 2.2) vs (6.92 +/- 1.48) mg x h x L(-1) (in * 1/ *3 vs * 1/ * 1 subjects), and CL/F were (9.1 +/- 1.2) vs (20.1 +/- 4.6) mL x min(-1), respectively. Statistic analysis results indicated that lornoxicam AUC(0-infinity) was significantly higher (2. 2-fold) and subsequently CL/F was significantly lower (55% ) in CYP2C9 * 1/ * 3 subjects than those in * 1/ * 1 subjects (P < 0.001).

CONCLUSION

CYP2C9 * 3 greatly affects both the pharmacokinetic profiles of glibenclamide and lornoxicam. The elimination of these drugs significantly decreased in subjects with CYP2C9 * 1/ * 3 genotype, especially lornoxicam.

Fast-dissolving mucoadhesive microparticulate delivery system containing piroxicam

We have studied the feasibility of preparing fast-dissolving mucoadhesive microparticulate delivery systems containing amorphous piroxicam to improve drug residence time on sublingual mucosa and drug dissolution rate. Two new mucoadhesive carriers, Eudragit L100 (EuLNa) and Eudragit S100 (EuSNa) sodium salts, both characterized by a fast intrinsic dissolution rate, have been selected. Microparticles containing piroxicam and EuLNa (series 1) or EuSNa (series 2) in ratios from 15/85 to 85/15% (m/m) were prepared by spray drying. The morphology and physical state of the microparticles and the effect of the microparticle composition on the piroxicam release and mucoadhesion were investigated. Piroxicam loaded into the microparticles was found to be in the amorphous form at all drug/copolymer ratios. This feature was ascribed to the presence of an H-bond between the NH of piroxicam and a CO of the copolymers. The formation of solid solutions improved the dissolution rate and the apparent drug solubility. The mucoadhesive properties were affected by the drug/copolymer ratio and in series 2 the microparticles containing more than 50% (m/m) of piroxicam did not show mucoadhesive properties. The delivery system made of piroxicam and EuLNa in the ratio 70/30% (m/m) appears to be the most promising because it contains the lowest amount of polymer able to confer mucoadhesive properties and increase apparent drug solubility.

Topical absorption of piroxicam from organogels—in vitro and in vivo correlations

In view of their good skin tolerability, glyceryl fatty acid esters were used as organogelators, and their effects in the topical penetration of piroxicam (Px) were investigated. The in vivo skin penetration was evaluated by measuring the anti-inflammatory effect in rats, where we found that Px incorporated into glyceryl fatty acid ester organogels exhibited a significantly greater inhibition of oedema than that of the placebo control either when applied locally (p < 0.001), or via transdermal absorption (p < 0.01 and < 0.05, respectively). As the Px concentration was increased, the extent of oedema inhibition rose in accordance with a power law. Comparisons with traditional galenic organogels and a marketed product revealed that the relative biological availability of Px was better from glyceryl fatty acid ester organogels, except when calculated for D1 versus T2 and T3. In order to predict the extent of in vivo skin absorption, we measured the penetration coefficient and the in vitro penetration. In accordance with theory, the extent of in vivo oedema inhibition increased as P(oct/w) increased, and maximum inhibition was observed at logP = 2.0211. However, the in vitro penetration through a synthetic membrane did not correlate with the in vivo results, the reason for which might be the different natures of the model barriers.

Skin permeation enhancement by sucrose esters: A pH-dependent phenomenon

The purpose of the present study was to evaluate the effect of sucrose esters (particularly, sucrose laureate and sucrose oleate in Transcutol) on the percutaneous penetration of a charged molecule as a function of ionization. We have investigated the influence of these sucrose esters on the in vitro diffusion profiles of lidocaine hydrochloride, a weak ionizable base (pKa=7.9), at different pH values, using porcine ear skin as the barrier membrane. As expected, lidocaine flux in the absence of an enhancer, increased from pH 5 to 9 with a corrresponding increase in the level of the unionized base. However, when skin was pretreated with 2% laureate in Transcutol (2% L-TC), drug permeation was higher at pH 5.0 and 7.0 than at 9.0. A different trend was observed in experiments with 2% oleate in Transcutol (2% O-TC), where skin flux was maximal at a more basic pH, when the degree of ionization is low. The results suggest that sucrose laureate enhances the penetration of the ionized form of the drug (12-fold greater flux relative to control), whereas sucrose oleate is more effective in promoting permeation of the unionized species. The structural properties of the sucrose esters as well as the degree of ionization of the drug are important characteristics affecting the transdermal flux of lidocaine.

Lornoxicam pharmacokinetics in relation to cytochrome P450 2C9 genotype

AIMS

To investigate the pharmacokinetics of lornoxicam and the relationship with CYP2C9 polymorphism in healthy Chinese subjects.

METHODS

A single oral dose of 8 mg lornoxicam was administered to 18 healthy Chinese male subjects. Plasma was sampled for 24 h post dose, and plasma concentrations of lornoxicam were measured using a validated LC/MS/MS method. CYP2C9 genotype was determined by polymerase chain reaction-based restriction fragment length polymorphism or by direct sequencing of the coding region of the CYP2C9 gene.

RESULTS

Of the 18 subjects, one subject was found to be a very poor metabolizer of lornoxicam with a long t(1/2) of 106 h, a low CL/F of 0.71 ml min(-1), and a high AUC(0-infinity) of 187.6 microg ml(-1) h. Genotyping studies revealed that this subject was heterozygous for CYP2C9*3 and a new variant CYP2C9 allele. Of the other 17 subjects, 13 were *1/*1 carriers, three were *1/*3 carriers, and one was a *1/*2 carrier. Mean AUC(0-infinity) values (95% confidence intervals) of lornoxicam were 9.25 (6.55, 11.95) vs. 4.75 (3.55, 5.95) microg ml(-1) h in *1 heterozygotes vs.*1 homozygotes, and mean CL/F values were 14.8 (10.2, 19.4) vs. 32.9 (24.5, 41.3) ml min(-1), respectively (P < 0.05 for both AUC and CL/F).

CONCLUSIONS

The results show that the pharmacokinetics of lornoxicam are dependent on CYP2C9 polymorphism. In particular, the presence of the CYP2C9*3 allele impairs the oral clearance of lornoxicam.

Pharmacokinetic profiles of two tablet formulations of piroxicam

There is considerable interest in developing new non-steroidal anti-inflammatory drugs (NSAIDs) formulations with faster onset of analgesic action like fast dissolving tablets. An open-label, randomized, single dose, crossover study with a 18 days washout period was conducted in 16 healthy volunteers to compare the pharmacokinetic profile of 20 mg piroxicam freeze-dried tablet (Proxalyoc, Cephalon) with that of 20 mg piroxicam capsule (Feldene, Pfizer). T(lag) with freeze-dried tablet was three times shorter than with capsule (21.6 min versus 59.4 min). Mean AUC(0-30 min), mean AUC(0-1 h), mean plasma concentrations at 15 min, 30 min and 1 h post-dose were significantly higher with the freeze-dried tablet than with the capsule, indicating that piroxicam was more rapidly absorbed from the freeze-dried tablet with higher plasma concentrations achieved at shorter intervals after dosing. The 90% confidence intervals of the ratios of means C(max), AUC(0-t), AUC(0-infinity) and T(1/2) all fell within the acceptance range of 0.8-1.25, demonstrating the bioequivalence of the two formulations. Although the bioavailability of the two formulations was similar, the administration of piroxicam as a freeze-dried tablet gave a much faster absorption rate during the first hour after dosing than the capsule formulation. This faster absorption is an obvious advantage for the treatment of acute episodes of pain.

Enhanced bioavailability of piroxicam via salt formation with ethanolamines

Piroxicam can be ionized as a zwitterion that has two pKa values (pKa1=1.86 and pKa2=5.46). Consequently, piroxicam has a low solubility in both polar and nonpolar media, and a low lipophilicity, which results in a low permeability. Three piroxicam-ethanolamine salts were prepared, which had a higher area under the curve (AUC) than piroxicam. There were minimal differences in the AUC among the salt forms. It was reported that the piroxicam triethanolamine salt had a lower permeability across the skin than piroxicam but it had a higher oral bioavailability. Piroxicam monoethanolamine showed the highest Cmax followed by piroxicam diethanolamine and piroxicam triethanolamine. The dissolution rates of piroxicam and its salts were similar at pH 1.2. Piroxicam monoethanolamine showed the highest dissolution rate at pH 6.8, which was followed by the piroxicam diethanolamine and piroxicam triethanolamine salts. The order of dissolution rate at pH 6.8 matched the order of Cmax or the AUC after oral administration.

In vitro and in vivo percutaneous absorption of topical dosage forms: case studies

This article evaluated the influence of vehicle compositions on topical drug availability. In vitro drug release and in vivo experiments were performed in case of the hydrophilic ketamine hydrochloride and the lipophilic piroxicam. Ketamine hydrochloride is a NMDA receptor antagonist that has been useful for anesthesia and analgesia. The study of transdermal ketamine delivery is a novelty, because nobody has investigated the hypnotic effects of ketamine after this administration route. In vitro measurements gave a good basis for screening among the developed products. The physiological changes after ketamine administration showed, that there were significant differences among the parameters tested (breathing rate, duration of sleep) from the developed products (hydrogel, lyotropic liquid crystal and o/w cream) compared to the reference product (Carbopol gel). The in vivo feedback for piroxicam was the measurement of the anti-inflammatory activity by edema inhibition percentage. Significant differences were measured in case of the developed systems compared to the reference.

Dehydration kinetics of piroxicam monohydrate and relationship to lattice energy and structure

The dehydration kinetics of piroxicam monohydrate (PM) is analyzed by both model-free and model-fitting approaches. The conventional model-fitting approach assuming a fixed mechanism throughout the reaction is found to be too simplistic. The model-free approach allows for a change of mechanism and activation energy, Ea, during the course of a reaction and is therefore more realistic. The complexity of the dehydration of PM is illustrated by the dependence of Ea on both the heating conditions, isothermal or nonisothermal, and on the fraction of conversion, alpha (0 < or = alpha < or = 1). Under both isothermal and nonisothermal conditions, Ea increases with alpha for 0 < or = alpha < or = 0.25, followed by an approximately constant value of Ea during further dehydration. In the constant-Ea region, isothermal dehydration follows the two-dimensional phase boundary model (R2), whereas nonisothermal dehydration follows a mechanism intermediate between two- and three-dimensional diffusion that cannot be described by any of the common models. Structural studies suggest that the complex hydrogen-bond pattern in PM is responsible for the observed dehydration behavior. Ab initio calculations provide an explanation for the changes in the molecular and crystal structures accompanying the reversible change in hydration state between anhydrous piroxicam Form I and PM. This work also demonstrates the utility of model-free analysis in describing complex dehydration kinetics.

Cyclodextrin enhanced transdermal delivery of piroxicam and carboxyfluorescein by electroporation

The transdermal transport of cyclodextrins (CD) across porcine epidermis by electroporation was studied. Electroporation increased the permeation of beta-cyclodextrin (BCD) and hydroxy propyl beta-cyclodextrin (HPCD) by several orders of magnitude, relative to passive transport. The presence of BCD and HPCD enhanced the total transport of the test permeants piroxicam and carboxyfluorescein (CF), respectively, from both permeant solutions and suspensions. BCD enhanced the fraction of piroxicam transported across the epidermis into the receiver compartment medium. This was most likely due to the prolonged post-pulse permeability state of the epidermis. The fraction of CF retained in the epidermis was increased by HPCD. The rate of diffusion of CF from epidermis into the receiver compartment was decreased by the presence of HPCD, apparently due to the aggregate forming tendency of HPCD. The in vivo delivery of CF by electroporation in mice demonstrated the potential of HPCD for sustaining the transdermal absorption rate of hydrophilic molecules.

Transbuccal permeation, anti-inflammatory activity and clinical efficacy of piroxicam formulated in different gels

In attempts to avoid the systemic side effects of piroxicam (PC) (e.g. gastrotoxicity), several buccal gel formulations containing PC were prepared and their effects on the characteristics of the drug permeation through rabbit buccal mucosa in-vitro were evaluated using a Franz-type diffusion cell. The general rank order of the total flux of 0.5% PC from gels was found to be: hydroxypropylmethylcellulose (HPMC, 2.5%) > hydroxypropylcellulose (HPC, 2.5%) >or= sodium alginate (Na alg., 7%) > methylcellulose (MC, 3%) > hydroxyethylcellulose (HEC, 1.5%) > carbopol 934 (Carb. 934, 1%) >or= sodium carboxymethylcellulose (NaCMC, 2%) > pluronic F-127 (PF-127, 20%) > polyvinyl alcohol (PVA, 10%). The effect of various penetration enhancers 1% sodium lauryl sulphate (NaLS), 3% sodium deoxycholate (NaDC), 3% sodium tauroglycocholate (NaTGC) on the rate of permeation across the excised buccal mucosa (of 0.5% PC in gels prepared using 3% MC, 2.5% HPMC or 7% Na alg. base) and histology of the buccal epithelium was also investigated. Pharmacodynamic evaluation of the anti-inflammatory activity of PC in these gel formulations (containing 3% NaDC as an enhancer) was carried out using the kaolin-induced rat paw oedema method. The results obtained indicated that PC administered in 7% Na alg. or 2.5% HPMC gel bases was significantly more effective than the 3% MC gel and oral drug solution in suppressing oedema formation in rats. Comparative clinical studies were conducted in patients with post-operative dental pain and oedema following maxillofacial operations. The results revealed that 7% Na alg. and 2.5% HPMC gel formulations applied to the buccal mucosa were slightly better than or equally effective to the orally administered commercial product (Feldene Flash) tablet) in reducing pain level, swelling and tenderness within a period of 4 days. These findings suggest that PC (0.5%) administered in the buccal gel may present a potential therapeutical use as a strong anti-inflammatory and analgesic agent.

CYP2C9 genotypes and the pharmacokinetics of tenoxicam in Brazilians

OBJECTIVE

Cytochrome P450 (CYP) 2C9, the product of the polymorphic gene CYP2C9, provides the major catabolic pathway for several anti-inflammatory drugs, including tenoxicam. Our objectives were (1) to determine the frequency of 2 common CYP2C9 variant alleles (*2 and *3) in the Brazilian population and (2) to evaluate the effects of these polymorphisms on the pharmacokinetics of tenoxicam.

METHODS

Polymerase chain reaction-restriction fragment length polymorphism methods were used to identify CYP2C9*2 and CYP2C9*3 in 331 healthy Brazilians, classified as white (n = 136), black (n = 77), or intermediate (n = 118). A validated HPLC procedure was used for measuring the plasma concentrations of tenoxicam, after single oral doses of 20 mg, administered to 21 individuals with CYP2C9*1/*1 (n = 12), CYP2C9*1/*2 (n = 4), or CYP2C9*1/*3 genotypes (n = 5), confirmed by deoxyribonucleic acid sequencing. A 2-compartment pharmacokinetic model was used for fitting the plasma concentration versus time data, and the individual model descriptive parameters were used to simulate the plasma tenoxicam concentrations during repeated dosing for 7 consecutive days.

RESULTS

The frequencies of CYP2C9*1, CYP2C9*2, and CYP2C9*3 in the study population were 0.849, 0.086, and 0.065, respectively. The distribution of CYP2C9 alleles differed across the Brazilian color groups (P = .016), with the frequencies of the variant alleles being 2.5 to 3 times lower in black Brazilians than in white Brazilians (P = .003). After a single dose of tenoxicam, the area under the plasma concentration-time curve (AUC) from time 0 to infinity and the oral clearance of tenoxicam were 190 +/- 48 microg x mL(-1) x h and 113 +/- 30 mL x h(-1), respectively, in wild-type homozygous subjects (CYP2C9*1/*1), as compared with 261 +/- 14 microg x mL(-1) x h (P = .013) and 77 +/- 4 mL x h(-1) (P = .036), respectively, in CYP2C9*1/*2 heterozygous subjects and 335 +/- 126 microg x mL(-1) x h (P = .003) and 67 +/- 23 mL x h(-1) (P = .008) in CYP2C9*1/*3, respectively, heterozygous subjects. After 7 simulated daily doses, significant differences were observed between CYP2C9*1/*1 and CYP2C9*1/*3 individuals in relation to the minimum plasma (trough) tenoxicam concentration (Cmin, 5.2 +/- 1.3 microg x mL(-1) versus 7.6 +/- 2.6 microg x mL(-1); P = .021), maximum tenoxicam plasma concentration (Cmax, 7.4 +/- 1.9 microg x mL(-1) versus 10.5 +/- 3.0 microg x mL(-1); P = .020), and 24-hour AUC (152 +/- 39 microg x mL(-1) x h versus 219 +/- 72 microg x mL(-1) x h). No significant differences were observed in Cmin, Cmax, or AUC between CYP2C9*1/*2 and either CYP2C9*1/*1 or CYP2C9*1/*3 individuals.

CONCLUSION

The allelic and genotypic frequencies of CYP2C9*1, *2, and *3 in white and black Brazilians are similar to those reported for other white (Caucasian) and black (African and African American) populations, respectively. Heterozygosis for CYP2C9*3, and to a lesser degree CYP2C9*2, increases the exposure to tenoxicam during single and repeated doses.

Synthesis of Chitosan Microspheres Containing Pendant Cyclodextrin Moieties and their Interaction with Biological Active Molecules

A new route to obtain chitosan derivatives containing cyclodextrin moieties as pendant groups was developed. The chitosan microspheres, obtained through crosslinking with glutaraldehyde of an acetic acid solution of chitosan, in an organic suspension medium, were reacted with chloroacyl cyclodextrins in organic basic solvents. The acyl cyclodextrin moieties are linked to the chitosan microspheres through C-N bonds, with the elimination of HCl; higher amounts of acyl cyclodextrin are linked to the microspheres with a smaller crosslinking degree. The chitosan-cyclodextrin conjugates retain higher amounts of bioactive substances (nalidixic acid, piroxicam) or of p-nitrophenol (model substance) than their parent chitosan supports, both by ionic forces and by the formation of inclusion complexes in the cyclodextrin inner cavities. After these preliminary studies, one can appreciate that the cyclodextrin-chitosan conjugates could be used as supports for chromatographic separations or controlled release drug systems.

Multicomponent Complexes of Piroxicam with Cyclodextrins and Hydroxypropyl Methylcellulose

The purpose of the study was to investigate the effect of hydroxypropyl methylcellulose (HPMC) on the complexation of piroxicam (PX) with beta-cyclodextrin (beta-CD) and dimethyl-beta-cyclodextrin (DM-beta-CD) in solution and in the solid state. Phase solubility study revealed a positive effect of the polymer on the drug complexation. Improvement in stability constants values, Ks, of ternary complexes clearly proves the benefit of the HPMC addition for promoting higher complexation efficiency. Solid binary and ternary complexes were prepared by spray drying. Drug-CD and drug-CD-polymer interactions were studied in the solid state by differential scanning calorimetry (DSC), zeta-potential measurements, and particle size distribution. A marked increase in the PX dissolution rate was observed even in binary and ternary complexes. The presence of HPMC in ternary complexes slightly retarded the release of PX. Cyclodextrin complexation increased the PX concentration gradient over the semipermeable membrane, resulting in an increased PX flux. The retarded diffusion of PX to the membrane interface decreased the PX flux values of the ternary complexes.

Preparation and characterization of reverse micelle based organogels of piroxicam

The solubilization of piroxicam to increase transdermal permeation rate was attempted by incorporating the drug in reverse micelle systems consisting of lecithin/isopropyl myristate/water [RMS-1] and sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane/water [RMS-2]. The change in polarity of water present in the water pool formed by reverse micelles resulted in a solubilization of piroxicam. These systems were used for the formation of reverse micellar organogels RMO-1 and RMO-2 by means of either varying hydration ratio (Wo) or by addition of a macromolecule, e.g. gelatin, into the system or by taking both the parameters in consideration. These systems were evaluated for physical properties, toxicology, in vitro and in vivo transdermal permeation. Significant (p < 0.01) inhibition of carrageenan induced rat paw oedema was observed for products RMO-1 and RMO-2 and a marketed transdermal product after 3 h.

[Determination of lornoxicam in human plasma by LC/MS/MS]

AIM

To develop a sensitive and specific LC/MS/MS method for determination of lornoxicam in human plasma and investigate pharmacokinetics of single dose of lornoxicam in healthy Chinese volunteers.

METHODS

Lornoxicam and the internal standard piroxicam were extracted from plasma using liquid-liquid extraction, then separated on a Zorbax XDB-C8 column. The mobile phase consisted of methanol-water-formic acid (80:20:0.5) at a flow-rate of 0.7 mL.min-1. A Finnigan TSQ tandem mass spectrometer equipped with atmospheric pressure chemical ionization source was used as detector and operated in the positive ion mode. Selected reaction monitoring (SRM) using the precursor-->product ion combinations of m/z 372-->121 and m/z 332-->121 was used to quantify lornoxicam and internal standard, respectively.

RESULTS

The linear calibration curves were obtained in the concentration range of 2.0-1,600 micrograms.L-1. The limit of quantitation was 2.0 micrograms.L-1. The method was successfully used in the pharmacokinetic study for lornoxicam. The main parameters obtained after an oral dose of 8 mg lornoxicam to 18 Chinese male volunteers were as follows: the value of T1/2 was (4.7 +/- 1.1) h, AUC0-infinity was found to be (5.5 +/- 2.4) mg.h.L-1. However, T1/2 of 105 h and AUC0-infinity of 189.5 mg.h.L-1 were obtained for another volunteer.

CONCLUSION

The method is proved to be suitable for clinical investigation of lornoxicam pharmacokinetics, which offers advantages of specificity, speed, and higher sensitivity over the previously reported methods.

Three-month, zero-order piroxicam release from monodispersed double-walled microspheres of controlled shell thickness

Double-walled microspheres represent an increasingly important class of drug delivery devices that provide enhanced control of drug delivery schedules. Clearly, the overall particle size and shell thickness are important parameters in modulating the drug release rates. Precision particle fabrication technology has been used to fabricate double-walled microspheres of predefined uniform diameters of 40-60 microm exhibiting a poly(D,L-lactide-co-glycolide) (PLG) core and poly(L-lactide) (PL) shell of controllable thickness from approximately 2 to 10 microm. The release of a model small-molecule drug, piroxicam, from uniform microspheres of pure PLG and PL is compared to the release from double-walled microspheres exhibiting different PL shell thicknesses. The presence of the PL shell enveloping a PLG core essentially eliminated the initial "burst" of piroxicam that was observed when the drug was released from pure PLG microspheres. In addition, increasing the PL shell thickness shifted the release profile from a biphasic shape for pure PLG microspheres to zero-order piroxicam release over 3 months for the thickest (approximately 10 microm) PL shell.

The detection of piroxicam, tenoxicam and their metabolites in equine urine by electrospray ionisation ion trap mass spectrometry

An investigation has been conducted into the metabolism and urinary excretion of orally administered piroxicam and tenoxicam in the horse. The major component detected in urine after the administration of piroxicam was 5'-hydroxypiroxicam, which was detectable up to 24 h post-administration. Unchanged piroxicam was present only as a minor component. In contrast, unchanged tenoxicam was the major component observed after the administration of tenoxicam, being detectable for 72 h post-administration, while 5'-hydroxytenoxicam was a minor component. Phase II beta-glucuronide conjugation in each case was found to be negligible. The ion trap mass spectral characteristics of piroxicam, tenoxicam, 5'-hydroxypiroxicam and 5'-hydroxytenoxicam under electrospray ionisation conditions were examined in some detail.

Influence of cyclooxygenase inhibitors on the central histaminergic stimulations of hypothalamic - pituitary - adrenal axis

Brain histamine participates in central regulation of the hypothalamic-pituitary-adrenal (HPA) axis. Endogenous prostaglandins modulate signal transduction of different neurotransmitters involved in activation of HPA axis. In the present experiment we investigated whether endogenous prostaglandins are involved in the stimulation of ACTH and corticosterone secretion by histaminergic systems in the rat brain. Histamine (50 microg), histamine-trifluoromethyl-toluidine derivative (HTMT, 75microg) a selective and potent H(1)-receptor agonist, and amthamine (50 microg) a H(2)-receptor agonist given intracerebroventricularly (i.c.v.) to non-anesthetized rats considerably increased ACTH and corticosterone secretion 1h after administration. A non-selective cyclooxygenase inhibitor indomethacin (2 mg/kg i.p. or 10 microg i.c.v.), piroxicam (0.02 and 0.2 microg i.c.v.) a more potent antagonist of constitutive cyclooxygenase (COX-1) and compound NS-398 (0.1 and 1.0 microg i.c.v.), a selective inhibitor of inducible cyclooxygenase (COX-2) were given 15 min before histamine and histamine receptor agonists. One hour after the last injection trunk blood from decapitated rats was collected for hormones determination. The histamine-induced ACTH and corticosterone secretion was significantly diminished by piroxicam and was not markedly altered by indomethacin and compound NS-398. The HTMT-elicited increase in ACTH and corticosterone secretion was significantly prevented by indomethacin and was not affected by piroxicam or compound NS-398. The amthamine-evoked increase in ACTH and corticosterone secretion was not markedly influenced by any cyclooxygenase blocker applied in the present experiment. These results indicate that the histamine H(1)-receptor transmitted central stimulation of the HPA axis is considerably mediated by prostaglandins generated by consititutive cyclooxygenase, whereas stimulation transmitted via H(2)-receptor does not significantly depend on endogenous prostaglandins mediation.

Enhanced bioavailability of piroxicam using Gelucire 44/14 and Labrasol: in vitro and in vivo evaluation

Piroxicam is a non-steroidal anti-inflammatory drug that is characterized by low solubility and high permeability. The purpose of the study was to investigate the in vitro and in vivo performance of the semi-solid dispersion prepared with Gelucire 44/14 and Labrasol into hard gelatin capsules (GL) for enhancing the dissolution rate of the drug. The results were evaluated by comparing with pure piroxicam filled into hard gelatin capsules (PP) and a commercially available tablet dosage form containing a piroxicam:beta-cyclodextrin complex (CD). The in vitro dissolution testing of the dosage forms was performed in different media (simulated gastric fluid, pH 1.2; phosphate buffers, pH 4.5 and 6.8; and water). Amongst the dosage forms, GL provided at least 85% piroxicam dissolution within 30 min in each of the media, behaving like a fast-dissolving immediate release drug product. Oral bioavailability of 20 mg piroxicam in GL, CD, and PP was compared after administration of a single dose to eight healthy volunteers. Three treatments were administered in crossover fashion, separated by a washout period of 2 weeks. Piroxicam was monitored in plasma by high-performance liquid chromatography. The apparent rate of absorption of piroxicam from GL (Cmax=2.64 micrograms/ml, tmax=82.5 min) was significantly higher than that of the PP (Cmax=0.999 micrograms/ml, tmax=144 min) (P<0.05) and similar to that of CD (Cmax=2.44 micrograms/ml, tmax=120 min) (P>0.05). The relative bioavailability values as the ratios of mean total AUC for GL relative to PP and CD, were 221 and 98.6%. Piroxicam is characterized by a slow and gradual absorption via the oral route and this causes a delayed onset of therapeutic effect. Thus, plain piroxicam preparations are not indicated for analgesia. The results of the in vivo study revealed that the GL dosage form would be advantageous with regards to rapid onset of action, especially in various painful conditions where an acute analgesic effect is desired.

Single dose pharmacokinetics of piroxicam in cats

Piroxicam (PIRO) is a nonsteroidal anti-inflammatory drug (NSAID) recognized for its value as a chemopreventative and anti-tumor agent. Eight cats were included in this study. PIRO was administered in a single oral (p.o.) and intravenous (i.v.) dose of 0.3 mg/kg. The study was designed as a randomized complete crossover with a 2-week washout period. Serial blood samples were collected after each dose and plasma was analyzed for PIRO. Pharmacokinetic parameters of PIRO were determined using noncompartmental analysis. PIRO is well absorbed in the cat with a median bioavailability (F) of 80% (range 64-124%). The median i.v. t1/2 was 12 h (range 8.6-14 h). The median Cmax was 519 ng/mL with a corresponding Tmax of 3 h. PIRO appears to be rapidly absorbed following p.o. administration in cats with a higher Cmax and AUC than in dogs.

Dissolution, bioavailability and ulcerogenic studies on piroxicam-nicotinamide solid dispersion formulations

Solid dispersions with different ratios of Piroxicam and Nicotinamide (as a carrier) were prepared by fusion method. Drug-carrier interactions in the solid state were ascertained using phase-diagram, X-ray diffraction (XRD) and Differential scanning colorimetry (DSC). Select ratios of the formed piroxicam-nicotinamide solid dispersions and their corresponding physical mixtures were formulated into tablets and capsules. The dissolution characteristics of the formed solid dispersions, physical mixtures and their formulations were compared with pure piroxicam in 900 ml of 0.1 N HCl (pH 1.2) at 37 +/- 0.5 degrees C, 50 rpm using USP XXI paddle apparatus. Solid dispersion capsule PNC1 (containing 1:5--drug-carrier ratio solid dispersion) and the corresponding physical mixture capsule PNC1A were used for bioavailability studies in healthy human volunteers. Further, ulcer indices of the prepared solid dispersion and their corresponding physical mixture were compared with pure piroxicam in rats. The DSC, XRD and phase diagram indicated the formation of solid dispersed system. The prepared dispersion showed better dissolution than the corresponding physical mixture and pure drug. The fabricated formulation complied with the pharmacopoeial limits for physico-chemical properties and the solid dispersion capsules PNC1 and PNC2 (containing 1:9 ratio of drug to carrier solid dispersion) showed 3 and 6.6 fold increase and 3.2 and 8 fold increases in dissolution rate compared to the corresponding physical mixture capsules (PNC1A and PNC2A), respectively. The solid dispersion capsule PNC1 showed significantly higher absorption and dissolution and consequently better bioavailability than the corresponding physical mixture capsule (PNC1A) in healthy human volunteers. The ulcer indices of the prepared dispersions were significantly lower than the corresponding physical mixture and pure drug.

Effect of ethanolamine salts and enhancers on the percutaneous absorption of piroxicam from a pressure sensitive adhesive matrix

The effects of salt formation on the percutaneous absorption of piroxicam through hairless mouse skin from a pressure sensitive adhesive (PSA) matrix were investigated. We also studied the effect of permeation enhancers on the skin permeation of piroxicam or piroxicam-ethanolamine (PX-EA) salts from an acrylic adhesive matrix. The order of the permeation rates of piroxicam and PX-EA salts from the PSA matrix was piroxicam-monoethanolamine salt (PX-MEA)>piroxicam-diethanolamine salt (PX-DEA)>piroxicam>piroxicam-triethanolamine salt (PX-TEA). The enhancer Crovol A40 provided the highest piroxicam and PX-MEA fluxes and Plurol oleque the highest PX-DEA and PX-TEA fluxes. The order of piroxicam and PX-EA salts permeabilities were different for saturated solutions in various enhancers and PSA matrix containing the same enhancer, especially when Crovol A40, Crovol PK40 or Plurol oleque were used as enhancers. No close relationship was found between the fluxes of piroxicam or PX-EA salts from saturated solutions and from PSA matrices containing the same enhancer. Maximum piroxicam flux was obtained when PX-MEA/PX-TEA (4:6, v/v) was incorporated into a PSA matrix containing Crovol PK40.

Development and in vitro evaluation of an enteric-coated multiparticulate drug delivery system for the administration of piroxicam to dogs

The aim of the study was to develop enteric-coated pellets for the administration of piroxicam (a poorly water-soluble drug) to small animals in order to avoid local gastrointestinal irritation, one of the major side effects of nonsteroidal anti-inflammatory drugs after oral ingestion. Pellets were made by an extrusion-spheronization process. The influence of several excipients on the in vitro drug release was evaluated. Piroxicam release from the uncoated pellets was measured in phosphate buffer (pH 6.8) using the paddle dissolution method (USP XXIII). The enteric-coated pellets were tested in 0.1 N HCl and phosphate buffer, pH 6.8. The addition of sodium croscarmellose (Ac-Di-Sol) did not influence the piroxicam release from microcrystalline cellulose pellets. Sodium carboxymethyl starch (Explotab) increased the release from 30 to 65% at 45 min. The incorporation of sodium carboxymethyl cellulose on its own or as a co-processed blend with microcrystalline cellulose (Avicel RC 581 and CL 611) enhanced the release of piroxicam at 45 min from 30% (pure Avicel PH 101) to 95% (combination of Avicel PH 101 and CL 611 in a ratio of 1:3). Additional use of cyclodextrins had only a minor influence on the dissolution rate. An Eudragit L 30 D-55 and FS 30 D (6/4) film was applied to the core pellets (containing 2.5% (w/w) piroxicam and a combination of Avicel PH 101 and CL 611 in a ratio of 1:3) in order to obtain gastroresistant properties. The coated pellets retained their dissolution characteristics after compression into fast disintegrating tablets because waxy cushioning beads were added to minimize film damage.

Enhanced percutaneous absoption of piroxicam via salt formation with ethanolamines

PURPOSE

The aim of this work was to prepare piroxicam-ethanolamine salts (PX-EAs) with improved physicochemical properties for transdermal application.

METHODS

The physicochemical properties of prepared salts were investigated by DSC and FT-IR. Their percutaneous absorption characteristics across hairless mouse skin and the effect of various enhancers were studied using a flow-through diffusion cell system.

RESULTS

Three piroxicam-ethanolamine salts were prepared. Piroxicam monoethanolamine salt (PX-MEA) and piroxicam diethanolamine salt (PX-DEA) had higher solubility than piroxicam in most of vehicles tested and a higher permeation rate across the skin. The solubility and permeation rate of piroxicam triethanolamine salt (PX-TEA) was lower than those of piroxicam in most of vehicles tested. However, there was no significant change in octanol/water partition coefficient by salt formation. Salt formation lowered the melting point of piroxicam and, of the systems examined, PX-DEA showed the lowest melting point. When the effect of various enhancers were evaluated, nonionic surfactants having medium HLB, an alkyl chain length of C18 and an ethylene oxide chain were better able to modify the permeability of the stratum corneum and to promote the effective penetration of piroxicam and PX-EAs.

CONCLUSIONS

Piroxicam salt formation with MEA and DEA improved the physicochemical properties and enhanced the skin permeability of piroxicam.

Studies of piroxicam absorption by oral mucosa

The present study was undertaken to investigate, if the non-steroidal anti-inflammatory drug (NSAID) piroxicam (CAS 36322-90-4) Fast-Dissolving Dosage Form (FDDF) can be absorbed in the oral mucosa. Piroxicam FDDF was administrated under the tongue to rats with an oesophagus ligation (OL) to prevent the drug entering the stomach and in turn its absorption by the classic way. A group of sham-operated (SO) animals received the same piroxicam FDDF dose. After drug administration, a pharmacokinetic study with serial serum sample extractions at 0, 15, 30, 60 and 120 min was performed. It has been found a prompt increase in serum piroxicam levels in OL-rats, which showed different pharmacokinetics from SO-rats. Areas under curve (AUCs) of OL-rat serum piroxicam levels were higher at 15, 30 and 60 min compared to SO-animals. These results indicate that piroxicam FDDF is absorbed in the rat oral mucosa. Moreover, during the first hour, drug absorption by oral mucosa rendered higher piroxicam levels than gastric absorption.

Enhancement of dissolution rate and anti-inflammatory effects of piroxicam using solvent deposition technique

Piroxicam solid depositions were prepared by means of the solvent deposition technique using different concentrations of microcrystalline cellulose as carrier material. The solvent deposition system (SDS) with drug to carrier ratio of 1:9 had a rapid dissolution rate in vitro. When this SDS was administered perorally to rats with a previous experimentally induced inflammation in their paws, it exhibited a pronounced anti-inflammatory action. X-ray diffraction and infrared (IR) spectroscopy showed no differences in the crystal state of piroxicam in SDS formulation and physical mixture of piroxicam and carrier. The increase in the dissolution rate and consequent enhancement of anti-inflammatory effect of piroxicam in SDS were attributed to the reduced particle size of drug deposited on the carrier and enhanced wettability of the particles brought about by the carrier.