Absorption Of Indomethacin Research Articles

Feasibility of a High-Dose Inhaled Indomethacin Dry Powder with Dual Deposition for Pulmonary and Oral Delivery

In this study we have developed a high-dose dry powder inhaler formulation of indomethacin using a novel approach to carrier-based formulations. Specifically, larger drug particles serve as the carrier for the smaller micronized drug particles, such that an inhaled dose is combined with an oral dose. To study this system, the aerosol performance of a standard indomethacin–lactose formulation was compared to carrier-free micronized indomethacin and a drug-as-carrier formulation (a micronized indomethacin–coarse indomethacin blend). Indomethacin with lactose showed a very poor aerosol performance, indicating high adhesion between the drug and carrier. The performance of the carrier-free micronized drug was significantly better, indicating low cohesion. Coarse drug particles as a carrier allowed improved powder flow and aerosol performance while also providing a potential secondary route of absorption of indomethacin, namely oral. An optimal formulation ratio of 1:1 (w/w) fine indomethacin–coarse indomethacin was developed in this study.

Biopharmaceutics of Topical Ophthalmic Suspensions: Importance of Viscosity and Particle Size in Ocular Absorption of Indomethacin.

Eye drops of poorly soluble drugs are frequently formulated as suspensions. Bioavailability of suspended drug depends on the retention and dissolution of drug particles in the tear fluid, but these factors are still poorly understood. We investigated seven ocular indomethacin suspensions (experimental suspensions with two particle sizes and three viscosities, one commercial suspension) in physical and biological tests. The median particle size (d50) categories of the experimental suspensions were 0.37–1.33 and 3.12–3.50 µm and their viscosity levels were 1.3, 7.0, and 15 mPa·s. Smaller particle size facilitated ocular absorption of indomethacin to the aqueous humor of albino rabbits. In aqueous humor the AUC values of indomethacin suspensions with different particle sizes, but equal viscosity, differed over a 1.5 to 2.3-fold range. Higher viscosity increased ocular absorption 3.4–4.3-fold for the suspensions with similar particle sizes. Overall, the bioavailability range for the suspensions was about 8-fold. Instillation of larger particles resulted in higher tear fluid AUC values of total indomethacin (suspended and dissolved) as compared to application of smaller particles. Despite these tear fluid AUC values of total indomethacin, instillation of the larger particles resulted in smaller AUC levels of indomethacin in the aqueous humor. This suggests that the small particles yielded higher concentrations of dissolved indomethacin in the tear fluid, thereby leading to improved ocular bioavailability. This new conclusion was supported by ocular pharmacokinetic modeling. Both particle size and viscosity have a significant impact on drug concentrations in the tear fluid and ocular drug bioavailability from topical suspensions. Viscosity and particle size are the key players in the complex interplay of drug retention and dissolution in the tear fluid, thereby defining ocular drug absorption and bioequivalence of ocular suspensions.

Effect of supersaturation on absorption of indomethacin and tadalafil in a single pass intestinal perfusion rat model, in the absence and presence of a precipitation inhibitor

The effect of the degree of supersaturation (DS) on absorption of the model drugs indomethacin and tadalafil was elucidated in a single-pass intestinal perfusion (SPIP) model in rats. In addition, the performance of the precipitation inhibitor (PI) hydroxypropylmethylcellulose (HPMC) was evaluated when added at a concentration of 0.1% (w/v) to fasted state simulated intestinal fluid (FaSSIF and FaSSIFHPMC) used as perfusion medium.A supersaturated state was created by a solvent shift method where indomethacin or tadalafil dissolved in dimethyl sulfoxide (DMSO) were administered to a segment of the small intestine, which subsequently was perfused with FaSSIF or FaSSIFHPMC. The perfusate was collected for 60 min, and for one group of rats dosed with 30 mg tadalafil, for 120 min. Blood samples were drawn every 15 min. The solubility of indomethacin and tadalafil in the perfusate was determined. The DS of each drug in the perfusate was calculated by dividing the concentration in the perfusate at selected time points with the solubility. The DS was above one for all timepoints for both drugs, thus showing supersaturation during the time of perfusion. For indomethacin, no improvement of the DS was seen when perfusing with FaSSIFHPMC, compared to FaSSIF. For tadalafil, a higher DS was achieved when perfusing with FaSSIFHPMC compared to FaSSIF. Perfusing the drugs with FaSSIFHPMC resulted in a significantly lower area under the curve (AUC0-60 min) for plasma concentrations of indomethacin, and no increase in the AUC0-60 min of plasma concentrations of tadalafil compared to perfusion with FaSSIF.The importance of simultaneously estimating the intraluminal DS and absorption of a drug was demonstrated by the SPIP model in the present study. Further, the study highlights the discrepancy between optimal in vitro supersaturation, intraluminal supersaturation and in vivo performance of two poorly soluble drugs, and further emphasizes the importance of optimization of in vitro methods in order to predict in vivo supersaturation and precipitation of drugs.

Study of the Inhibitory Effects of Enteral Nutrition Formula on Indomethacin-Induced Gastric Lesions in Mice.

We investigated the effects of enteral nutrition formula on non-steroidal anti-inflammatory drug (NSAID)-induced gastric lesions in mice. Male ICR mice aged 7–9 weeks old were fasted, then orally given either purified water, Mermed® One, or 2-fold diluted Terumeal® 2.0α as enteral nutrition (25 or 50 mL/kg each). Indomethacin (IND) was orally administered at 20 mg/kg after 30 min, and the stomach was removed 6 h later and fixed in formalin. The number and area of lesions in the stomachs of the mice given enteral nutrition showed a significant, dose-dependent decrease compared to the purified water-treated group, and no significant difference was seen between the two enteral nutrition-treated groups. Comparable time courses of plasma IND concentrations suggest that enteral nutrition does not inhibit gastrointestinal absorption of IND. Our findings indicate that administering enteral nutrition could inhibit the onset of NSAID-induced gastric ulcers.

Development of microparticles coated with poly-γ-glutamic acid to improve oral absorption of a poorly water-soluble drug

Novel microparticles coated with poly-γ-glutamic acid (PGA) were developed to improve the oral absorption of indomethacin (IM), a poorly water-soluble drug. Microparticles containing γ-IM (IMbulk-PGA) or crystal polymorph α-IM (IMpolymorph-PGA) were prepared. Additionally, microparticles were prepared containing α-IM without PGA (IMpolymorph without PGA). IMbulk-PGA and IMpolymorph-PGA exhibited better drug retention properties on mucin disks. Drug release rates from IMpolymorph-PGA and IMpolymorph without PGA were higher than from IM bulk powder, and drug release from IMbulk-PGA was also improved. Drug release from IMbulk-PGA could be improved with the use of Tween 80. In addition, PGA may influence the ionization of IM or affect specific molecular interactions. After the microparticles were administered orally to mice, IMbulk-PGA and IMpolymorph-PGA increased the plasma drug concentration more rapidly compared with IM bulk powder, but IMpolymorph without PGA did not increase the plasma drug concentration. It was considered that IMbulk-PGA and IMpolymorph-PGA rapidly reached the intestinal membrane through the mucus layer and IM was absorbed quickly. Because IMbulk-PGA and IMpolymorph-PGA showed a rapid increase in plasma drug concentration, IMbulk-PGA and IMpolymorph-PGA could be useful preparations to improve the gastrointestinal absorption of IM. Furthermore, IMbulk-PGA may maintain higher plasma drug concentrations than IMpolymorph-PGA.

In vitro and in vivo evaluation of porous lactose/mannitol carriers for solubility enhancement of poorly water-soluble drugs

The application of porous materials as drug carriers represents a new solubility enhancement strategy for poorly soluble drugs. In this study, porous lactose or mannitol carriers were prepared by a combined spray drying and template removal method with Indomethacin loaded as a model drug. In vitro dissolution test and in vivo absorption study were employed to evaluate the capacity of the porous carriers on solubility enhancement of Indomethacin. Porous lactose carriers displayed higher surface area and larger pore volume than that of mannitol, which was consistent with the corresponding amount of drug loading. Compared with the physical mixtures, indomethacin loaded into the porous carriers displayed significantly higher dissolution rate, with more than 80% of the loaded drug released in 10 min. Results of animal experiments in beagle dogs showed that the prepared Indomethacin-loaded porous lactose can enhance the in vivo absorption of Indomethacin. The analysis in gender difference suggested that Indomethacin was absorbed faster in female beagle dogs than that in male. The fabrication of porous framework from food-grade materials and the proved effectiveness on solubility enhancement further expand the capability of spray drying engineering of pharmaceutical particles.

Pharmacokinetics and safety of low-dose submicron indomethacin 20 and 40 mg compared with indomethacin 50 mg

Introduction. Indomethacin is a potent analgesic that, similar to other nonsteroidal anti-inflammatory drugs, is associated with serious dose-related adverse events. There is a need for newer nonsteroidal anti-inflammatory drug products with improved tolerability. Low-dose submicron indomethacin was developed using SoluMatrix Fine Particle Technology™ to enable treatment at lower doses than commercially available indomethacin drug products. This study evaluated the pharmacokinetics and safety of submicron indomethacin 20 and 40 mg compared with indomethacin 50-mg capsules. Methods. This was a phase 1, randomized, open-label, 4-period, 4-sequence, single-dose crossover study. Forty healthy volunteers received low-dose submicron indomethacin 20- or 40-mg capsules, or indomethacin 50-mg capsules under fasting or fed conditions. Pharmacokinetic parameters and safety were assessed. Results. Comparable fasting peak plasma levels (mean ± standard deviation) were demonstrated for submicron indomethacin 40 mg (2368.79 ± 631.38 ng/ml) and indomethacin 50 mg (2369.40 ± 969.06 ng/ml). The overall systemic exposure (geometric least squares mean; 95% CI) was > 21% lower for submicron indomethacin 40 mg (6007.71 ng·h/mL; 5585.73–6461.58) compared with indomethacin 50 mg (7646.23 ng·h/ml; 7110.44–8222.40) under fasting conditions. Food delayed the rate but did not affect the extent of indomethacin absorption from submicron indomethacin 40 mg. Submicron indomethacin 40 mg administration resulted in earlier time to peak plasma levels (median 1.67; min–max 0.5–3.5 hours) under fasting conditions compared with indomethacin 50 mg (2.02; 0.5–5.0 hours). Submicron indomethacin 20 and 40 mg were dose proportional and generally well tolerated. Conclusion. Compared with indomethacin 50 mg, submicron indomethacin 40 mg achieved similar peak plasma concentrations, lower systemic exposure, and a faster time to peak plasma concentration, indicating rapid absorption. The current formulation of low-dose submicron indomethacin has recently demonstrated efficacy in 2 phase 3 studies in patients with acute pain following bunionectomy and represents a new, low-dose treatment option for patients with acute pain.

Effects of the Various Solvents on the In vitro Permeability of Indomethacin through Whole Abdominal Rat Skin

Purpose : The aim of the present study was to evaluate the effect of some solvents on in vitro dermal absorption of indomethacin. Methods: The effects of different solvents such as Plurololeique, Labrasol, Tween 80, Isopropyl myristate and PEG 400 on indomethacin permeation through pretreated rat skin were evaluated. A specially designed Franz diffusion cell was used and the data were compared to the results of hydrated abdominal rat skin as a common control. The measured permeability parameters included permeability coefficient (Kp), diffusion coefficient (D) and flux (Jss). Enhancement mechanisms were studied by comparing changes in peak wave number position and their intensities of asymmetric (Asy) and symmetric (Sym) C-H stretching, lipid ester carbonyl stretching in SC, C=O stretching (Amide I) and C-N stretching of keratin (Amide II) absorbance using Fourier transform infrared spectroscopy (FTIR). Using differential scanning calorimetry (DSC), their mean transition temperature (Tm) and enthalpies ( ∆H) were also compared. Results : All the solvent materials significantly increased flux (Jss) (p<0.05), with isopropyl myristate

Mechanistic investigation and reversible effect of 2-isopropyl-5-methylcyclohexyl heptanoate on the in vitro percutaneous absorption of indomethacin

In the present study, the enhancing effect of 2-isopropyl-5-methylcyclohexyl heptanoate (M-HEP) on the percutaneous absorption of indomethacin (IM) was evaluated by the in vitro penetration experiments using the rat abdominal skin as a barrier. Partition experiment, attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectrum and transepidermal water loss (TEWL), was employed to investigate the possible mechanisms of the action of M-HEP. Furthermore, the reversible effect of M-HEP on excised rat skin was also evaluated through in vitro permeation as a preliminary indicator of safety. The result of in vitro permeation experiment indicated that, 10% (w/w) M-HEP in combination with isopropyl palmitate (IPP) significantly increased (p < 0.05), the cumulative amount of IM in comparison with the control group (IPP only). The partition coefficient of IM between the stratum corneum (SC) and enhancer solution was also greater than that between the SC and IPP. A blue shift in the ATR-FTIR spectra of SC after treatment with M-HEP solution was observed at the CH2 band, which indicating that M-HEP disrupted the intercellular lipid structure of the SC. In addition, both M-HEP/IPP and L-menthol (MT)/IPP improved the TEWL value of rat abdominal skin. After removal of M-HEP, the skin barrier function would be restored in 8 h. In conclusion, M-HEP could reversibly enhance the percutaneous absorption of IM by increasing the partitioning of IM into the SC from enhancer solution and disturbing the organized structure of SC lipids and the reversibility of M-HEP was better than MT.

Development and comparative evaluation of extended release indomethacin capsules

The aim of this study was to develop a new extended release capsules of indomethacin. The formulation has been prepared to enhance its dissolution which could provide better oral absorption of indomethacin (IND). Therefore, the effects of the component nature, their proportion in the release rate and the dissolution mechanism were investigated. Extended release capsules of IND were prepared by physical mixing using plasdone (PVP K-90) and compritol-HD5 ATO (Comp) at various drug-polymer ratios. Flow properties of the physical mixtures were evaluated by calculation of the Carr’s index, angle of repose and Hausner ratio. According to the United States Pharmacopeial (USP) drug release criteria of IND extend release capsules, the release results of formulations F2 and F3 were found to be similar to the USP (P < 0.05). Certain mathematical models were used for evaluation of release profiles and the results supported by multiple regression analysis. It was observed that the best-fit model to determine the mechanism of the formulation which has shown the highest release was Higuchi square-root of time model (r2 = 0.969). According to the dissolution results, dissolution efficiency, relative dissolution rate and mean dissolution time were also evaluated. The results of the study indicated that new extended release hard gelatin capsules can be a promising alternative for the other oral formulations of IND. Key words: Indomethacin, drug release, kinetic evaluation, hard gelatine capsule, stability, multiple regression analysis.

Effectiveness of submicronized chitosan-coated liposomes in oral absorption of indomethacin

The plasma profile of indomethacin (IMC) after oral administration of IMC-loaded submicronized chitosan-coated liposomes (ssCS-Lip) was evaluated to reveal the effectiveness of the mucoadhesive function for improving the absorption of this poorly absorbable drug. The stomach and small intestine were removed from rats after 1, 2, and 4 hours of oral administration of submicron-sized liposomes (ssLip) or ssCS-Lip containing fluorescent dye, and the retentive properties were confirmed by measuring the amount of dye in each part of the gastrointestinal (GI) tract. Results showed that ssCS-Lip tended to be better retained in the upper part of the GI tract, compared with ssLip, at 1, 2, and 4 hours after administration, and was significantly better retained in the small intestine at 4 hours. The plasma profile and bioavailability of IMC after oral administration of both types of liposomes were improved, compared with oral administration of IMC solution. The maximum residence time of ssCS-Lip was significantly longer than those of ssLip. The extended plasma profile of ssCS-Lip was attributed to its prolonged retention in the upper region of the GI tract, and its delayed migration to the lower part of the intestine, the neutral pH of which is more soluble for IMC, an acidic drug. Therefore, the chitosan-coated ssLip, with its higher retention in the GI tract, is a promising drug carrier for the oral administration of poorly absorbed compounds.

Hepatic and renal toxicities of indomethacin acid, salt form and complexed forms with hydroxypropyl‐β‐cyclodextrin on Wistar rats after oral administration

Indomethacin (IM), a non-steroidal anti-inflammatory drug, has the capacity to induce hepatic and renal injuries when administrated systemically. The aim of this study is to assess the IM absorption from complexed forms when orally administered to rats, by means of a comparative evaluation of its capacity to induce hepatic and renal injury in different forms, namely IM acid, IM sodium salt or IM complexed with hydroxypropyl-β-cyclodextrin (HP-β-CD), using freeze- and spray-drying methods. A total of 135 Wistar rats weighing 224.4 ± 62.5 g were put into 10 groups. They were allowed free access to water but were maintained on fast for 18 h before the first administration until the end of the experiment. Water and HP-β-CD (control groups) and IM acid form, IM trihydrated-sodium-salt and IM-HP-β-CD spray- and freeze-dried, at normal and toxic doses (test groups), were orally administered once/day for 3 days. Seventy-two hours after the first administration, the animals were sacrificed and a fragment of the liver and one kidney were collected and prepared for histopathological evaluation. Lesion indexes (rated 0/4 for liver and 0/3 for kidney) were developed and the type of injury scored according to the severity of damage. A statistical analysis of the severity and incidence of lesions was carried out. Animals administered with IM complexed forms showed similar hepatic and renal lesions, both in toxic and therapeutic doses, when compared with those observed in animals administered with IM acid or salt forms. This suggests that under the present experimental conditions, IM is equally absorbed from the gastrointestinal tract, independently of the administered IM form.

ChemInform Abstract: Transdermal Delivery of Drugs and Enhancement of Percutaneous Absorption

This paper describes 1) the drug delivery through the skin to produce systemic effects, 2) the enhancement of percutaneous absorption by absorption enhancers, heating and complex formation, 3) the mechanism for the enhancement effect by enhancers, 4) the percutaneous absorption of peptides, and 5) the pharmacokinetic analysis for percutaneous absorption. 1,3-Dinitroglycerin, indomethacin (IND) and many drugs were efficiently absorbed via rat and rabbit skins in the presence of some enhancers, and using a microporous membrane therapeutic plasma concentrations were maintained for a long time. Enhancement of percutaneous absorption by the complex formation with fatty acid was observed for propranolol (PL) in vitro and in vivo. Heating at 42-45 degrees C also enhanced the percutaneous absorption dramatically, with decreased activation energies. The following mechanisms for the enhancement effect by enhancers were found: a) an increase in the fluidity of the stratum corneum lipids and reduction in the diffusional resistance to permeants, b) the removal of intercellular lipids and dilation between adherent cornified cells, c) an increase in the thermodynamic activity of drugs in vehicles, d) the exfoliation of stratum corneum cell membranes, the dissociation of adherent cornified cells and elimination of the barrier function. Peptides such as enkephalin, elcatonin and insulin were effectively absorbed through the skin in the presence of some enhancers and specific inhibitors, with no proteolytic degradation. The pharmacokinetic model with two parallel absorption processes, lipidic and aqueous pore transport pathways, in skin could adequately describe the percutaneous absorption of IND, PL and valproic acid. With peptides, a kinetic model including zero-order input rate, first-order permeation rate and first-order degradation rate was able to describe well the steady-state flux of peptides.

A novel mechanism for oral controlled release of drugs by continuous degradation of a phospholipid prodrug along the intestine: In-vivo and in-vitro evaluation of an indomethacin–lecithin conjugate

Purpose To investigate a novel mechanism for oral controlled release of drugs involving a continuous degradation of a phospholipid prodrug along the intestine. An indomethacin–lecithin conjugate with the drug attached to the sn-2 position of the phospholipid through a 5-carbon linker (DP-155) was used as a model molecule. Methods The pharmacokinetics of DP-155 and free indomethacin liberated from the prodrug following intravenous, oral or intra-colon administration was investigated in rats, and evaluated in comparison to free indomethacin administration. Degradation by phospholipase A 2 (PLA 2) enzymes was assessed in-vitro. The impact of the linker length was evaluated in comparison to an indomethacin–phospholipid conjugate with a shorter linker (2-carbons). Results Following oral or intra-colon DP-155 administration, free indomethacin was liberated along the intestine and absorbed into the systemic circulation, resulting in a controlled release profile of indomethacin in the plasma. The shorter linker caused a 20-fold decrease in the subsequent indomethacin absorption. DP-155 in-vitro degradation by PLA 2 was over 60%, while shorter linkers were profoundly less degradable. Conclusions DP-155 caused a continuous input of free indomethacin into the plasma following degradation by PLA 2 in the gut lumen. Since the rate of drug release is not formulation dependent, the prodrug can be compounded even in a liquid dosage form. The phospholipid–drug conjugate is thus a potential novel mechanism for oral controlled release of drugs.

Cubosome Dispersions as Delivery Systems for Percutaneous Administration of Indomethacin

The present study concerns the production and characterization of monooleine (MO) dispersions as drug delivery systems for indomethacin, taken as model anti-inflammatory drug. Dispersions were produced by emulsification and homogenization of MO and poloxamer in water. Morphology and dimensional distribution of the disperse phase have been characterized by cryo-transmission electron microscopy and photon correlation spectroscopy, respectively. X-ray diffraction has been performed to determine the structural organization of the disperse phase. Sedimentation field flow fractionation (SdFFF) has been performed to investigate drug distribution in the dispersion. An in vitro diffusion study was conducted by Franz cell associated to stratum corneum epidermis membrane on cubosome dispersions viscosized by carbomer. In vivo studies based on skin reflectance spectrophotometry and tape stripping were performed to better investigate the performance of cubosome as indomethacin delivery system. Microscopy studies showed the coexistence of vesicles and cubosomes. X-ray diffraction revealed the presence of a bicontinuous cubic phase of spatial symmetry Im3m (Q229). SdFFF demonstrated that no free drug was present in the dispersion. Indomethacin incorporated in viscosized MO dispersions exhibited a lower flux with respect to the analogous formulation containing the free drug in the aqueous phase and to the control formulation based on carbomer gel. Reflectance spectroscopy demonstrated that indomethacin incorporated into MO dispersions can be released in a prolonged fashion. Tape-stripping experiments corroborated this finding. MO dispersions can be proposed as nanoparticulate systems able to control the percutaneous absorption of indomethacin.

Poly n-butylcyanoacrylate (PNBCA) nanocapsules as a carrier for NSAIDs: in vitro release and in vivo skin penetration.

The aim of this work was to prepare poly n-butylcyanoacrylate (PNBCA) nanocapsules loaded with indomethacin and to evaluate the ability of this carrier system to deliver the drug systemically after its topical application. Poly n-butylcyanoacrylate (PNBCA) nanocapsules of indomethacin were prepared by interfacial polymerization. The physicochemical characterization of the PNBCA nanocapsules was performed by measuring the drug content by HPLC and analyzing the particle size using scanning electron microscopy. The in vitro permeation of indomethacin through excised rat skin and an artificial membrane was determined for PNBCA nanocapsules in pH 7.4 phosphate buffer (I), and in PLF-127 gel (II) and were compared against indomethacin incorporated into 25%w/w PLF-127 gel alone (III). The in vivo percutaneous absorption of indomethacin following the application of the PNBCA nanocapsules and a 25%w/w Pluronic F-127 (PLF-127) gel (III) was monitored by the determination of drug plasma levels in rats. The drug loading results indicated that approximately 76.6% of indomethacin was loaded onto the PNBCA nanocapsules; the average particle size was 188 nm. The in vitro results indicated a rank order for the three formulations (I, II and III) in both the flux at steady state and the cumulative amounts permeated at 8 hrs. The higher drug plasma levels over 6 hrs of indomethacin PNBCA nanocapsules are in agreement with the determined in vitro permeation results. The presented data show that indomethacin loaded PNBCA nanocapsules can improve the transdermal delivery of indomethacin compared to a conventional gel formulation using Pluronic F-127. This might be due to their ultra fine particle size and their hydrophilic and hydrophobic surface characteristics.

Inactivation of creatine kinase during the interaction of indomethacin with horseradish peroxidase and hydrogen peroxide: involvement of indomethacin radicals

Creatine kinase (CK) was used as a marker molecule to examine the side effect of damage to tissues by indomethacin (IM), an effective drug to treat rheumatoid arthritis and gout, with horseradish peroxidase and hydrogen peroxide (HRP–H 2O 2). IM inactivated CK during its interaction with HRP–H 2O 2. Under aerobic conditions, inactivation of CK significantly decreased. CK in rat heart homogenate was also inactivated by IM with HRP–H 2O 2. When IM was incubated with HRP–H 2O 2, the maximum absorption of IM at 280 nm rapidly decreased and a new peak at 410 nm occurred with isosbestic points at 260 and 312 nm. In contrast, under anaerobic conditions, the spectral change of IM was almost absent, indicating IM was oxidized to the yellow substance by HRP–H 2O 2. Adding catalase strongly inhibited the production of yellow substance. Sodium azide also blocked the formation of yellow substance and the inactivation of CK. Electron spin resonance signals of IM carbon-centered radical were detected using 2-methyl-2-nitrosopropane during the interaction of IM with HRP–H 2O 2 under anaerobic conditions. Oxygen was consumed during the interaction of IM with HRP-H 2O 2. These results suggest that IM carbon-centered radicals may rapidly react with O 2 to generate the peroxyl radicals. Sulfhydryl groups and tryptophane residues of CK decreased during the interaction of IM with HRP–H 2O 2. Other sulfhydryl enzymes, including alcohol dehydrogenase and glyceraldehyde-3-phosphate dehydrogenase, were also readily inactivated during the interaction with HRP–H 2O 2. Sulfhydryl enzymes seem to be very sensitive to IM activated by HRP–H 2O 2.

Enhanced absorption of indomethacin after oral or rectal administration of a self-emulsifying system containing indomethacin to rats

A self-emulsifying system (SES), a mixture of an oil and a surfactant which forms an oil-in-water emulsion, is expected to improve the in vitro drug dissolution and enhance the in vivo drug absorption. In this study, a poorly water-soluble drug, indomethacin (IDM) was incorporated into the SES to increase bioavailability. The SES with 30% of Tween 85 and 70% of ethyl oleate, EO (w/w) was selected as an optimized formulation (high drug loading, low surfactant concentration, and small particle size). After an oral administration of the SES containing IDM and IDM suspension, (IDM was suspended in methyl cellulose), 22.5 mg/kg as IDM, to rats, the area under the plasma concentration–time curve from time zero to the last measured time in plasma, 12 h (AUC 0–12 h) was significantly greater (57% increase) in the SES, suggesting that oral absorption of IDM increased significantly by the SES. After a rectal administration of gelatin hollow type suppositories, filled with the SES containing IDM and IDM powder physically mixed with the SES, 22.5 mg/kg, to rats, the AUC 0–12 h also increased significantly (41% increase) by the SES, suggesting that rectal absorption of IDM also increased significantly by the SES.

Effect of pulsed output ultrasound on the transdermal absorption of indomethacin from an ointment in rats.

The effect of pulsed output ultrasound (1 MHz) with on/off ratios of 1:2, 1:4 and 1:9 on transdermal absorption of indomethacin from an ointment was studied in rats. Ultrasound energy was supplied for between 10 and 19 min at a range of intensities (1.0-2.5 W.cm-2), energy levels commonly used for therapeutic purposes. The on/off pulsed ratio, intensity and the time of application were found to play an important role in the transdermal phonophoretic delivery system of indomethacin; 1:2 pulsed output ultrasound appeared to be the most effective in improving the transdermal absorption. The highest penetration was observed at an intensity of 1.0 W.cm-2 and application time of 15 min. With pulsed output it was possible to use higher intensities of ultrasound without increasing skin temperature or damaging skin.

Percutaneous absorption of indomethacin from pluronic F127 gels in rats.

Thermally reversible gels of the poly(oxyethylene)-poly (oxypropylene)-(polyoxyethylene) triblock copolymer, Pluronic F127, were evaluated as vehicles for the percutaneous administration of drugs using indomethacin as a model drug. In-vivo percutaneous absorption studies using a rat model suggest that a 20% w/w aqueous gel of Pluronic F127 may be of practical use as a base for topical administration of the drug. The addition of isopropyl myristate or (+)-limonene to the gel formulation significantly improved percutaneous absorption, particularly when the gel was applied using an occlusive dressing technique.