Controlled release alginate-chitosan microspheres of tolmetin sodium prepared by internal gelation technique and characterized by response surface modeling

Tolmetin sodium (TS) is a powerful non-steroidal mitigating drug for the treatment of rheumatoid joint inflammation, osteoarthritis, and adolescent rheumatoid joint pain. In addition to its gastrointestinal (GIT) problems, TS has a short biological half-life (1 hr). In a trial to overcome these side effects and control the rate of (TS) release, chitosan coated alginate microspheres are recommended. A Box-Behnken experimental design was employed to produce controlled release microspheres of TS in the sodium alginate and chitosan copolymers (Alg-Ch) by emulsification internal gelation methodology. The effect of critical formulation variables namely, drug to polymer ratio (D:P ratio), speed of rotation and span 80% on drug encapsulation efficiency (% EE), drug release at the end of 2 hours (Rel2) and drug release at the end of 8 hours (Rel8) were analyzed using response surface modeling. The parameters were assessed using the F test and mathematical models containing only the significant terms were generated for each parameter using multiple linear regression analysis. The produced microspheres were spherical in shape with extensive pores at D:P ratio 1:1 and small pores at a drug to polymer ratio (D:P ratio) 1:3. Differential scanning calorimetry (DSC) affirmed the steady character of TS in microspheres and revealed their crystalline form. All formulation variables examined exerted a significant influence on the drug release, whereas the speed emerged as a lone factor significantly influencing % EE. Increasing the D: P ratio decreases the release of the drug after two and 8 hours. The increase in speed results in an increase in drug release after two and eight hours. The drug release from the microspheres followed zero order kinetics. TS Alg-Ch microspheres exhibited a significant anti-inflammatory effect on incited rat paw edema after eight hours. These results revealed that the internal gelation technique is a promising method to control TS release and eradicate GIT side effects using Alg-Ch copolymers.

Determination of the scale of segregation of low dose tablets using hyperspectral imaging.

In this work, near infrared (NIR) hyperspectral imaging was used to quantify the spatial distribution of drug in tablets containing tolmetin sodium dihydrate. Hyperspectral data cubes were generated by imaging the same spatial region of a sample while illuminated by a laser at a different wavelength for each image. Images were generated for wavelengths ranging from 1100 to 2200 nm. Ten tablets with concentrations ranging from 0.0 to 10.0% w/w tolmetin were imaged, and the scales of segregation were calculated for the tablets. Lactose anhydrous was used as the diluent, and all mixtures contained 0.5% magnesium stearate as a lubricant. This research has shown hyperspectral imaging to be viable tool for quantifying segregation of low dose drugs in tablets.

Control of encapsulation efficiency in polymeric microparticle system of tolmetin.

Ethylcellulose microparticles containing tolmetin sodium, an anti-inflammatory drug, were prepared by a solvent diffusion method based on the formation of multiple W/O(1)/O(2)-emulsion. The drug used was TOL, which is water-soluble and n-hexane was used as the non-solvent. Important parameters in the evaluation of a microencapsulation technique are actual drug loading, the encapsulation efficiency, the yield, solvent systems, dispersed phase to continuous phase ratio (DP/CP ratio), composition of continuous phase, drug distribution in microparticles and stability of primary emulsion. A small volume of internal aqueous phase and volume of organic solvent were favorable to achieve high drug encapsulation efficiencies. Since drug release during the initial stages depends mostly on the diffusion escape of the drug, major approaches to prevent the initial burst have focused on efficient encapsulation of the drug within the microparticles. For this reason, control of efficiency and the extent of initial burst are based on common formulation parameters. Most parameters affect encapsulation efficiency and initial burst by modifying solidification rate of dispersed phase. In order to prevent many unfavorable events such as pore formation, drug loss, and drug migration that occur while the dispersed phase is in the semi-solid state, it is important to understand and optimize these variables.

Ionic liquid-based dynamic liquid-phase microextraction: application to the determination of anti-inflammatory drugs in urine samples.

Dynamic liquid-phase microextraction (dLPME) using an ionic liquid as acceptor phase is proposed for the determination of six non-steroidal anti-inflammatory drugs (NSAIDs) in human urine samples for the first time. The extraction is carried out in a simple and automatic flow configuration. The chemical affinity between the extractant (1-butyl-3-methylimidazolium hexafluorophosphate) and the analytes permits a selective isolation of the drugs from the sample matrix allowing also their preconcentration. The whole analytical method has been optimized taking into account all the chemical, physical and hydrodynamic variables. The proposed method is a valuable alternative for the analysis of these drugs in urine within the concentration range 0.1-10 microg mL(-1), allowing their determination at therapeutic and toxic levels. Limits of detection were in the range from 38 ng mL(-1) (indomethacin) to 70 ng mL(-1) (naproxen). The repeatability of the proposed method expressed as RSD (n=5) varied between 2.1% (flurbiprofen) and 3.8% (tolmetin).

Identification of zomepirac-S-acyl-glutathione in vitro in incubations with rat hepatocytes and in vivo in rat bile.

Zomepirac (ZP), a nonsteroidal anti-inflammatory drug that was withdrawn from use, is metabolized to zomepirac-1-O-acyl-glucuronide (ZP-1-O-G), a chemically reactive conjugate that has been implicated in the toxicity of the drug. In the present studies, we investigated the ability of ZP to become bioactivated to reactive metabolites that transacylate glutathione (GSH) forming ZP-S-acyl-glutathione thioester (ZP-SG) in vitro and in vivo in rat. When ZP (100 microM) was incubated with rat hepatocytes, ZP-SG was detected in incubation extracts by a sensitive selected reaction monitoring liquid chromatography/tandem mass spectrometry (LC/MS-MS) technique. The initial formation rate of ZP-SG was rapid and reached a maximum concentration of 0.24 +/- 0.03 nM after 4 min of incubation, then decreased, in a fairly linear fashion, to 0.07 +/- 0.03 nM after 60 min of incubation. The product ZP-SG (1 microM) was shown to be unstable by undergoing rapid hydrolysis (apparent half-life approximately 0.8 min) in incubations with rat hepatocytes. After administration of ZP to a male Sprague-Dawley rat (100 mg/kg i.p.), bile was collected and analyzed for ZP-SG by LC/MS-MS. Results indicated the presence of ZP-SG in bile (6.7 microg excreted after 6 h of collection), which was confirmed by coelution with synthetic standard and by its tandem mass spectrum. Together, these results demonstrate that ZP becomes metabolically activated in vitro in rat hepatocytes and in vivo in rat to reactive acylating derivative(s), such as ZP-1-O-G, that transacylate GSH forming ZP-SG. Finally, we propose that ZP-SG thioester could be used as a marker derivative for mechanistic studies on the bioactivation of the drug.

Quantitation of tolmetin by high-performance liquid chromatography and method validation.

A high-performance liquid chromatographic (HPLC) assay method for assessing the degradation of tolmetin (TLM) is developed and validated under acidic, basic, and photoirradiated conditions. The HPLC method includes an Inertsil 5 ODS-3V column (250- x 4.6-mm i.d.), guard column of Inertsil 7 ODS-3V (50- x 4.6-mm i.d.), mobile phase of CH(3)OH-1% HOAc (64:36, v/v), and UV detection at 254 nm. The developed method satisfies the system suitability criteria, peak integrity, and resolution for the parent drug and its degradants. The established assay method exhibits good selectivity and specificity suitable for stability measurements. From the intra- and interday tests of six replicates, the coefficients of variation are between 0.20% and 1.77% for the former, and 0.12% and 3.40% for the latter. Recoveries are found to be 98.7-101.7%. TLM is determined to be more reactive when exposed to light and acidic conditions, yet TLM is stable in a basic medium. A kinetic study of the photodegradation of TLM shows that it follows an apparent first-order reaction in three alcoholic solvents.

Comparison of p-fluoroketorolac and [18O3]ketorolac for use as internal standards for the determination of ketorolac by gas chromatography/mass spectrometry (GC/MS).

A chemical and a stable-isotope analog, p-fluoroketorolac and [18O3]ketorolac respectively, were directly compared for applicability as internal standards for the determination of ketorolac in plasma samples using gas chromatography/mass spectrometry (GC/MS) with selective-ion-monitoring detection, following derivatization to form the methyl esters. This comparison involved analyzing ketorolac calibration standards and spiked plasma samples that contained both internal standard candidates. The response for ketorolac and each internal standard was monitored simultaneously and electronically integrated peak heights were obtained. Thus, for each analysis performed, a response ratio was obtained for each internal standard relative to an identical ketorolac response. Linearity of response for ketorolac calibration standards and accuracy for spiked plasma sample analysis were compared using each internal standard. The use of [18O3]ketorolac as the internal standard provided superior accuracy data for the analysis of ketorolac in plasma samples.

Preparative chromatography of furosemide 1-O-acyl-glucuronide from urine using micronized amberiite XAD-2 and its application to other 1-O-acyl-glucuronides.

Furosemide 1-O-acyl glucuronide (Fgnd) was extracted from the urine following oral administration of furosemide. The crude Fgnd was applied to micronized Amberlite XAD-2 column (2.5 cm i.d. x 90 cm length, 75-500 microns particle size). The purified Fgnd was identified by mass spectrometry and beta-glucuronidase treatment. This method was also applicable to the purification of glucuronide of tolmetin (nonsteroidal anti-inflammatory drug, NSAID), suggesting that it was applicable to the other NSAIDs, most of which were known to be metabolized to acyl-glucuronides.

Determination of diclofenac sodium, famotidine and ketorolac tromethamine by flow injection analysis using dichloronitrophenol.

Diclofenac sodium, famotidine and ketorolac tromethamine were determined by flow injection analysis (FIA) with spectrophotometric detection. The sample solutions (5-50 micrograms ml-1 of diclofenac sodium, 10-80 micrograms ml-1 of famotidine and 10-120 micrograms ml-1 of ketorolac tromethamine) in methanol were injected into a flow system containing 0.01% (w/v) of 2,4,dichloro-6-nitrophenol (DCNP) in methanol. The colour produced due to the formation of a charge transfer complex was measured with a spectrophotometric detector set at 450 nm. A sampling rate of 40 per hour was achieved with high reproducibility of measurements (RSD below 1.6%). The FIA method was applied to the determination of diclofenac sodium, famotidine and ketorolac tromethamine in pharmaceutical formulations.

Statistical optimization applied to the spectrophotometric study of a tolmetin-copper(II) complex.

Tolmetin sodium has been investigated and determined from dosage forms as its Cu(II) complex and method optimized by statistical optimization. The assay was developed using two mathematical statistical models: factorial design and response-surface mapping. The decision to apply experimental design techniques to the development of the method was made after a series of screening experiments revealed that the complex formation and extraction are maximized as a function of supporting electrolyte concentration, concentration of Cu(II) acetate and pH of the reaction mixture. One set of two-level three variable factorial experiments was carried out in order to evaluate the main effect, as well as the interaction among factors. The final step was to optimize the values of variables using response surface design. The best set of conditions was selected for further investigation.

Differential pulse polarographic assay of tolmetin sodium capsules.

Differential pulse polarography (DPP) is proposed as a direct method for the quantitation of tolmetin sodium in a capsule formulation (Tolectin--200 mg as the sodium dihydrate salt). Classical direct-current (DC) polarography has been employed to investigate the nature of the reduction occurring at the surface of the dropping mercury electrode (DME) using acetate buffer of pH 5.0 as the supporting electrolyte. The mean value of the results obtained by DPP expressed as a percentage of the stated amount, and the standard deviation, were found to be 99.87 +/- 0.43. The standard addition procedure used to assess the accuracy of the proposed method gave a mean percentage recovery of the total drug of 100.15 +/- 0.75%.

Statistical optimization of a reversed-phase ion-pair liquid chromatographic method for the analysis of tolmetin sodium in dosage forms.

A quantitative liquid chromatographic method in which tolmetin sodium is separated from an internal standard on a C18 column with detection at 317 nm has been developed with the aid of two statistical optimization procedures. The effects of simultaneously varying the pH, methanol-water ratio, and the concentrations of buffer and ion-pair reagent in the mobile phase were studied. A two-level factorial design was used to investigate the interactions among the variables, and the sequential simplex procedure was used to optimize the separation. A novel quality criterion was developed for the simplex optimization. Using synthetic mixtures, the mean recovery value +/- S.D. (n = 6) of tolmetin sodium was 98.7 +/- 0.19% for tablets and 98.5 +/- 0.12% for capsules. The assay results for commercial tablets and capsules were comparable to those obtained by the USP XXI procedure.

High-performance liquid chromatographic determination of tolmetin, tolmetin glucuronide and its isomeric conjugates in plasma and urine.

A rapid and sensitive analytical procedure is described for the simultaneous measurement of tolmetin (T), tolmetin glucuronide (1 beta-TG) and the isomers of tolmetin glucuronide in plasma and urine. A reversed-phase liquid chromatographic system is used with an ion-pairing mobile phase of methanol-tetrabutylammonium hydrogensulfate buffered to pH 4.5 and kept at a constant temperature of 50 degrees C. Detection is by UV at 313 nm. Plasma (0.5 ml) and urine (0.1 ml) are collected in pre-cooled containers and immediately adjusted to pH 3.0 to minimize TG isomerization and hydrolysis. Samples are then deproteinated with acetonitrile, the supernatant is evaporated to dryness and reconstituted in an acetate buffer (pH 4.5), and 50 microliters are injected onto the system. Using zomepirac as the internal standard, the measurable, linear concentration ranges are 0.05-50 micrograms/ml for T in plasma and 0.025-50 micrograms/ml for T in urine. Chromatographic peaks representing T,1 beta-TG and three isomers of TG were identified, all with retention times less than 10 min. The need for special handling of biological samples is discussed.

Continuous body fluid monitoring for zomepirac by fully automated high-performance liquid chromatography.

A sensitive, specific and rapid determination of 5-(4-chlorobenzoyl)-1,4-dimethyl-1H-pyrrole-2-acetic acid sodium salt dihydrate (zomepirac sodium, Zomax) in human plasma and urine by a continuous body fluid monitoring system based on high-performance liquid chromatography is described. Samples are directly injected into the apparatus which consists of commonly available HPLC-modules. Manual sample clean-up procedures as well as the addition of an internal standard are not needed. Using 50-microliter aliquots, the detection limit is lower than 0.05 microgram/ml and the calibration ranges from 0.5 to 100 micrograms/ml are linear for both, spiked samples and references. The recovery is 97% for plasma and 95% for urine samples at a sampling rate of about 15 samples/h.

Simultaneous determination of zomepirac and its major metabolite zomepirac glucuronide in human plasma and urine.

A method is described for the simultaneous determination of zomepirac and its primary metabolite, zomepirac glucuronide, in plasma and urine. Reversed-phase liquid chromatography is used with an ion-pairing mobile phase of methanol-tetrabutylammonium hydrogen sulfate. Detection is by UV at 313 nm. Biological samples are cooled immediately, then adjusted to pH 3 to avoid zomepirac glucuronide degradation. Samples (0.5 ml) are then deproteinated with acetonitrile or acetone, the supernatant concentrated and dissolved in acetonitrile-acetate buffer, with up to one half of the sample injected onto the LC system. Recovery is greater than 70% and reproducible. The measurable concentration range is linear from 0.05 to 200 micrograms/ml. Total elution time of the assay is less than 10 min. Selectivity of zomepirac and zomepirac glucuronide is optimized. Sample preparation prior to analysis so as to prevent zomepirac glucuronide degradation is emphasized.

[Screening and detection of the analgesic zomepirac]. / Screening und Nachweis des Analgetikums Zomepirac.

The article describes some possibilities for the screening and detection of the analgesic sodium [5-(4-chlorobenzoyl)-1,4-dimethylpyrrol-2-yl]-acetate dihydrate (zomepirac). UV-photometry seems to be the best method for the urine screening. Gas chromatography with and without derivatization and mass spectrometry are recommended as confirming methods.