Simple, rapid and sensitive method for the determination of indomethacin in plasma by high-performance liquid chromatography with ultraviolet detection

Amphiphilic Poly-N-vinylpyrrolidone Nanoparticles as Carriers for Nonsteroidal, Anti-Inflammatory Drugs: Pharmacokinetic, Anti-Inflammatory, and Ulcerogenic Activity Study

Nanoparticles are increasingly utilized as drug delivery agents. Previously, we have developed a drug delivery system based on amphiphilic derivatives of poly-N-vinylpyrrolidone (PVP-OD4000) with excellent biocompatibility. In the current study, we assessed the pharmacokinetics, anti-inflammatory profile, and ulcerogenic potential of indomethacin (IMC)-loaded PVP-OD4000 nanoparticles compared to the free drug. Wistar male rats were utilized for a pharmacokinetics study and an anti-inflammatory study. Loaded IMC exhibited a slower elimination rate (p < 0.05) and a higher blood plasma concentration at 8 and 24 h after intraperitoneal injection compared with free IMC. In addition, decreased uptake of loaded IMC in the liver and kidney compared to free IMC (p < 0.05) was detected. Furthermore, PVP-OD4000 nanoparticles loaded with IMC showed an enhanced anti-inflammatory effect compared to free IMC (p < 0.05) in carrageenan-induced and complete Freund’s adjuvant-induced−(CFA) sub-chronic and chronic paw edema treatment (p < 0.01; p < 0.01). Notably, upon oral administration of loaded IMC, animals had a significantly lower ulcer score and Paul’s Index (3.9) compared to the free drug (p < 0.05). The obtained results suggest that IMC loaded to PVP nanoparticles exhibit superior anti-inflammatory activity in vivo and a safe gastrointestinal profile and pose a therapeutic alternative for the currently available NSAIDs’ administration.

Supramolecular Complex of Ibuprofen with Larch Polysaccharide Arabinogalactan: Studies on Bioavailability and Pharmacokinetics

BACKGROUND AND OBJECTIVES

In the present work, pharmacological and pharmacokinetic properties of the supramolecular complex of non-steroid anti-inflammatory drug ibuprofen (IBU) with natural polysaccharide arabinogalactan (AG) were studied. The main goals of such complexation were the increase of ibuprofen's bioavailability and decrease its effective dose after oral administration.

METHODS

The complex with mass ratio as IBU:AG 1:10 was obtained by mechanochemical synthesis and characterized by water solubility, electron microscopy, differential scanning calorimetry, X-ray powder diffraction analysis and ¹H-nuclear magnetic resonance spectroscopy. Different animal models of pain and inflammation was used to investigate IBU:AG biological effects. Plasma concentration of IBU and its pharmacokinetic parameters were evaluated after oral introduction.

RESULTS

It was found that ibuprofen's effective analgesic and anti-inflammatory dose decreased twofold after its introduction as a complex with AG. The reason of this difference is due to the increase of ibuprofen concentration in rats' plasma: C _max of IBU at doses of 20 and 40 mg/kg was found as 0.088 and 0.132 μg/ml, whereas C _max of IBU in the complex form was 0.103 and 0.160 μg/ml, respectively.

CONCLUSIONS

Thus, we have shown that complexation of the IBU with AG results in its bioavailability increase, reduction of the effective dose and should decrease toxic side effects.

A liquid chromatography method with single quadrupole mass spectrometry for quantitative determination of indomethacin in maternal plasma and urine of pregnant patients

A liquid chromatography with single quadrupole mass spectrometry method was developed for the quantitative determination of indomethacin in the maternal plasma and urine of pregnant patients under treatment. A deuterium-labeled isotope of indomethacin (d4-indomethacin) was used as an internal standard. The maternal plasma and urine samples were acidified with 1.0M HCl then extracted with chloroform to achieve the extraction recovery range of 94-104% with variation less than 11%. Chromatographic separation was achieved by a Waters Symmetry C₁₈ column with isocratic elution of 0.05% (v/v) formic acid aqueous solution and acetonitrile (47:53, v/v). An in-source fragmentation was applied on the single quadrupole mass spectrometer equipped with an electrospray ionization source at positive mode. The LC-ESI-MS quantification was performed in the selected ion monitoring mode targeting ions at m/z 139 for indomethacin and m/z 143 for its internal standard. The calibration curves were linear in the concentration ranges between 14.8 and 2.97 × 10(3) ng/mL for plasma samples and between 10.5 and 4.21 × 10(3) ng/mL for urine samples. The relative standard deviation of this method was less than 8% for intra- and inter-day assays, and the accuracy ranged between 90% and 108%.

Quantitation of indomethacin in serum and plasma using gas chromatography-mass spectrometry (GC-MS)

Indomethacin is a non-narcotic and non-steroidal anti-inflammatory drug used in the treatment of various inflammatory diseases such as rheumatoid arthritis, osteoarthritis, and ankylosing spondylitis. In neonates, it is also used for induction of closure of patent ductus arteriosus (PDA). Its mechanism of action is believed to be through the inhibition of cyclooxygenase. Due to narrow therapeutic window and number of side effects, it's monitoring, particularly in neonates, is recommended. In the gas chromatography method described here, the drug is extracted from serum or plasma using methylene chloride and phosphate buffer (pH 6). The methylene chloride phase containing drug is separated and dried under stream of nitrogen. The drug is derivatized using Bis-(Trimethylsilyl)trifluoroacetamide (BSTFA) with 1% TMCS (trimethylchlorosilane). The derivatized drug is analyzed using gas chromatography-mass spectrometry. Quantitation of the drug in a sample is achieved by comparing responses of the unknown sample to the responses of the calibrators using selected ion monitoring. Meclofenamic acid is used as an internal standard.

Indomethacin promotes nitric oxide function in the ductus arteriosus in the mouse

BACKGROUND AND PURPOSE

Prenatal patency of ductus arteriosus is maintained by prostaglandin (PG) E(2) in concert with nitric oxide (NO) and carbon monoxide (CO). Accordingly, we have previously found that NO activity increases upon deletion of either COX. Here, we have examined whether COX inhibition by indomethacin mimics COX deletion in promoting NO.

EXPERIMENTAL APPROACH

Experiments were performed in vitro and in vivo with wild-type (WT) and eNOS-/-, near-term mouse foetuses. Indomethacin was given p.o. to the mother as single (acute treatment) or repeated (daily for 3 days; chronic treatment) doses within a therapeutic range (2 mg kg(-1)).

KEY RESULTS

Indomethacin promoted eNOS mRNA expression in the WT ductus. Coincidentally, the drug enhanced the contraction of the isolated ductus to the NOS inhibitor, N(G)-nitro-L-arginine methyl ester, and its effect augmented with the length of treatment. No such enhancement was seen with the eNOS-/- ductus. Chronic indomethacin also increased, albeit marginally, the contraction of the WT ductus to the CO synthesis inhibitor, zinc protoporphyrin. Whether given acutely or chronically, indomethacin induced a little narrowing of the ductus antenatally and had no effect on postnatal closure of the vessel.

CONCLUSIONS AND IMPLICATIONS

We conclude that activation of NO and, to a much lesser degree, CO mechanisms is an integral part of the indomethacin effect on the ductus. This relaxing influence may oppose the contraction from PGE(2) suppression and could explain the failures of indomethacin therapy in premature infants with persistent duct.

Sequential injection analysis (SIA)-chemiluminescence determination of indomethacin using tris[(2,2′-bipyridyl)]ruthenium(III) as reagent and its application to semisolid pharmaceutical dosage forms

Automated sequential injection (SIA) method for chemiluminescence (CL) determination of nonsteroidal anti-inflammatory drug indomethacin (I) was devised. The CL radiation was emitted in the reaction of I (dissolved in aqueous 50% v/v ethanol) with intermediate reagent tris(2,2'-bipyridyl)ruthenium(III) (Ru(bipy)(3)(3+)) in the presence of acetate. The Ru(bipy)(3)(3+) was generated on-line in the SIA system by the oxidation of 0.5mM tris(2,2'-bipyridyl)ruthenium(II) (Ru(bipy)(3)(2+)) with Ce(IV) ammonium sulphate in diluted sulphuric acid. The optimum sequence, concentrations, and aspirated volumes of reactant zones were: 15 mM Ce(IV) in 50mM sulphuric acid 41 microL, 0.5 mM Ru(bipy)(3)(2+) 30 microL, 0.4M Na acetate 16 microL and I sample 15 microL; the flow rates were 60 microLs(-1) for the aspiration into the holding coil and 100 microLs(-1) for detection. Calibration curve relating the intensity of CL (peak height of the transient CL signal) to concentration of I was curvilinear (second order polynomial) for 0.1-50 microM I (r=0.9997; n=9) with rectilinear section in the range 0.1-10 microM I (r=0.9995; n=5). The limit of detection (3sigma) was 0.05 microM I. Repeatability of peak heights (R.S.D., n=10) ranged between 2.4% (0.5 microM I) and 2.0% (7 microM I). Sample throughput was 180 h(-1). The method was applied to determination of 1 to 5% of I in semisolid dosage forms (gels and ointments). The results compared well with those of UV spectrophotometric method.

Local Delivery of Indomethacin to Arthritis-Bearing Rats through Polymeric Micelles Based on Amphiphilic Polyphosphazenes

PURPOSE

Preparation, in vitro and in vivo evaluation of indomethacin-loaded polymeric micelles based on amphiphilic polyphosphazene.

METHODS

Amphiphilic polyphosphazenes (PNIPAAm/EAB-PPPs) with poly (N-isopropylacrylamide) (PNIPAAm) and ethyl 4-aminobenzoate (EAB) as side groups were synthesized through thermal ring-opening polymerization and subsequent substitution reactions. Indomethacin (IND) loaded polymeric micelles based on PNIPAAm/EAB-PPPs were prepared by dialysis procedure. In vitro IND release kinetics was investigated in 0.1 M PBS (pH 7.4), while in vivo pharmacokinetics was performed in Sprague-Dawley rats. In vivo pharmacodynamic study was carried out based on two animal models, i.e. carrageenan-induced acute paw edema and complete Freund's adjuvant (CFA) induced ankle arthritis model.

RESULTS

Drug loading capacity of micelles based on this type of amphiphilic copolymers was mainly determined by copolymer composition and the chemical structure of drug. In addition to the compatibility between drug and micellar core, hydrogen bonding interaction between drug and hydrophilic corona may significantly influence drug loading as well. In vitro drug release in PBS suggested that there was no significant difference in release rate between micelles based on copolymers with various EAB content. Compared with the rats administered with free IND aqueous solution, IND concentration in rats' plasma showed a prolonged maintenance in experimental group treated with IND-loaded polymeric micelles. In vivo pharmacodynamic study indicated that sustained therapeutic efficacy could be achieved through topical injection of the aqueous solution of IND-loaded micelles. Local delivery of IND can avoid the severe gastrointestinal stimulation, which was frequently associated with oral administration as evidenced by ulceration evaluation.

CONCLUSIONS

The promising results of current preliminary study suggest that this type of amphiphilic copolymers could be used as injectable drug carriers for hydrophobic drugs.

Detection of indomethacin by high-performance liquid chromatography with in situ electrogenerated Mn(III) chemiluminescence detection

The determination of indomethacin (INM) in pharmaceutical and biological samples by means of high-performance liquid chromatography (HPLC) with in situ electrogenerated Mn(III) chemiluminescence (CL) detection was proposed. The method was based on the direct CL reaction of INM and Mn(III), which was in situ electrogenerated by constant current electrolysis. The chromatographic separation was carried out on Nucleosil RP-C(18) column (250 mm x 4.6 mm; i.d., 5 microm; pore size, 100 A) at 20 degrees C. The mobile phase consisted of methanol:water:acetic acid=67:33:0.1 solution. At a flow rate of 1.0 mL min(-1), the total run time was 10 min. The effects of several parameters on the HPLC resolution and CL emission were studied systematically. Under the optimal conditions, a linear range from 0.01 to 10 microg mL(-1)(R(2)=0.9991), and a detection limit of 8 ng mL(-1) (signal-to-noise ratio=3) for INM were achieved. The relative standard deviations (R.S.D.) for 0.1 microg mL(-1) INM were 2.2% within a day (n=11) and 3.0% on 5 consecutive days (n=6), respectively. The recovery of INM from urine samples was more than 92%. The applicability of the method for the analysis of pharmaceutical and biological samples was examined.

Indomethacin-loaded polymeric nanocarriers based on amphiphilic polyphosphazenes with poly (N-isopropylacrylamide) and ethyl tryptophan as side groups: Preparation, in vitro and in vivo evaluation

The effects of copolymer composition, drug structure and initial drug feed on drug loading of polymeric micelles based on amphiphilic polyphosphazenes were investigated. It was found that the drug loading capacity of micelles based on this type of amphiphilic copolymers was mainly determined by copolymer composition and the chemical structure of drug. In addition to the compatibility between drug and micellar core, hydrogen bonding interaction between drug and hydrophilic corona may significantly influence drug loading as well. In vitro drug release in 0.1 M PBS (pH 7.4) suggested that indomethacin (IND) in the micelles was released through Fickian diffusion, and no significant difference in release rate was observed for micelles based on copolymers with various EtTrp content. Compared with in vitro IND release profile, in vivo pharmacokinetic study after subcutaneous administration provides a more sustained release behavior. Additionally, in comparison with free drug solution at the same dose, IND concentration in rat plasma showed a prolonged retention when the drug was delivered through polymeric micelles. In vivo pharmacodynamic study based on both carrageenan-induced acute and complete Freund's adjuvant-induced adjuvant arthritis model indicated that sustained therapeutic efficacy could be achieved through intraarticular injection of IND-loaded micelles. Most importantly, local delivery of IND can avoid the severe gastrointestinal stimulation, which was frequently associated with oral administration.

Determination of indomethacin in plasma by micellar electrokinetic chromatography with UV detection for premature infants with patent ducts arteriosus

A simple and selective micellar electrokinetic chromatography (MEKC) is described for determination of indomethacin in plasma. Plasma proteins are precipitated by acetonitrile. An aliquot of supernatant was evaporated and reconstituted with Tris buffer for MEKC analysis. The separation of indomethacin was performed at 25 degrees C using a background electrolyte consisting of Tris buffer (30 mM; pH 8.0) with 100 mM sodium octanesulfonate (SOS) as an anionic surfactant. Under this condition, a good separation with high efficiency and short analysis time is achieved. Several parameters affecting the separation of indomethacin were studied, including pH and concentrations of the Tris buffer and SOS. The linear range of the method for the determination of indomethacin was over 0.3-10.0 microg/mL; the detection limit (signal-to-noise ratio=3; injection 0.5 psi 5s) was 0.1 microg/mL. The proposed method for determination of indomethacin in premature infants with patent ducts arteriosus has been demonstrated.

A rapid and sensitive microscale HPLC method for the determination of indomethacin in plasma of premature neonates with patent ductus arteriousus

Indomethacin (IND) is the drug of choice for the closure of a patent ductus arteriosus (PDA) in neonates. This paper describes a simple, sensitive, accurate and precise microscale HPLC method suitable for the analysis of IND in plasma of premature neonates. Samples were prepared by plasma protein precipitation with acetonitrile containing the methyl ester of IND as the internal standard (IS). Chromatography was performed on a Hypersil C(18) column. The mobile phase of methanol, water and orthophosphoric acid (70:29.5:0.5, v/v, respectively), was delivered at 1.5 mL/min and monitored at 270 nm. IND and the IS were eluted at 2.9 and 4.3 min, respectively. Calibrations were linear (r>0.999) from 25 to 2500 microg/L. The inter- and intra-day assay imprecision was less than 4.3 % at 400-2000 microg/L, and less than 22.1% at 35 microg/L. Inaccuracy ranged from -6.0% to +1.0% from 35 to 2000 microg/L. The absolute recovery of IND over this range was 93.0-113.3%. The IS was stable for at least 36 h when added to plasma at ambient temperature. This method is suitable for pharmacokinetic studies of IND and has potential for monitoring therapy in infants with PDA when a target therapeutic range for IND has been validated.

Development and validation of HPLC method for determination of indomethacin and its two degradation products in topical gel

Indomethacin forms by decomposition two degradation products: 4-chlorobenzoic acid and 5-methoxy-2-methylindoleacetic acid. They have to be monitored together with an active substance both during manufacturing process and storage of pharmaceuticals. European Pharmacopoeia (Ph. Eur. 4) describes titration method for determination of indomethacin, which is not very convenient in this case for practical use. Therefore, high performance liquid chromatography is the method-of-choice enabling determination of active substance and its degradation products during one-step procedure simultaneously and automatically. We have developed a fast, simple and fully automated analytical method for determination of indomethacin and its two impurities in pharmaceutical preparation using HPLC with UV detection. Various stationary phases were tested, especially new types of Zorbax columns made by Agilent. While the conventional C18 stationary phases were not convenient enough to achieve quick and reliable separation, Zorbax-Phenyl analytical column (75 mm x 4.6 mm, 3.5 microm) enables separation of indomethacin and its two degradation products during 7.5 min. Chromatography was performed using isocratic elution with binary mobile phase composed of acetonitrile and 0.2% phosphoric acid (50:50, v/v) at flow rate 0.6 ml/min. Even faster separation of standards was obtained with analytical column Zorbax SB-CN (150 mm x 4.6 mm, 5 microm). The separation was effected with mobile phase of the same composition, only the flow rate was increased to 1.2 ml/min. The analytical run was shortened to 5 min. Both methods use detection wavelength 237 nm and both can use either ketoprofen or flurbiprofen as internal standard for quantitation. The first method was finally chosen for validation because of the occurrence of placebo interferences in the case of using Zorbax SB-CN. System suitability parameters and validation parameters including method precision, accuracy, linearity, selectivity and robustness were set up. Afterwards, the method was successfully applied for the practical determination of indomethacin and its degradation products in a topical gel and for compound degradation control during stability studies.

Indomethacin-loaded methoxy poly(ethylene glycol)/poly(D,L-lactide) amphiphilic diblock copolymeric nanospheres: Pharmacokinetic and toxicity studies in rodents

Biodegradable methoxy poly(ethylene glycol)/poly(D,L-lactide) amphiphilic block copolymeric nanospheres were prepared for application as a particulate drug carrier. Drug-loaded nanospheres (ML50) showed a narrow size distribution with the average diameter of <200 nm. When the feed weight ratio of indomethacin (IMC) to polymer was 1:1, the ML50 nanosphere having a relatively high drug-loading efficiency of about 33.0% could be obtained. To investigate pharmacokinetic characteristics of IMC in rats, the IMC concentration in plasma was analyzed using a high-performance liquid chromatography system after intravenous bolus injection of free IMC and IMC-loaded ML50 nanospheres. ML50 nanosphere system exhibited a significant potential for sustained release of drug and showed slow clearance of IMC, but there was no significant effect on metabolism of IMC in the rats. Median lethal dose (LD50) and major organs (e.g., heart, lung, liver, and kidney) toxicities were determined using ICR mice to estimate the acute toxicity of ML50 nanospheres. The LD50 of ML50 nanospheres determined by Litchfield-Wilcoxon method was about 1.54 g/kg. After the mice were intraperitoneally administered with a half dose of LD50 for 7 days, no significant histopathologic changes were observed in ML50-treated mice compared with normal mice in the light and electron microscopic observations of major organs. This indicates that ML50 nanospheres might be a useful candidate as a novel sustained drug carrier for hydrophobic drugs.

Liquid chromatography method for determination of mefenamic acid in human serum

A simple, rapid and specific method for analysis of mefenamic acid (I) in serum by a sensitive high-performance liquid chromatography is described. Only 70 microl of serum and a little sample work-up is required. A simple procedure of extraction by dichloromethane followed by evaporation to dryness under gentle stream of nitrogen and dissolving the dried residue in mobile phase was used. The mefenamic acid peak was separated from endogenous peaks on a C(8) column by a mobile phase of acetonitrile-water (50:50, v/v, pH 3). Mefenamic acid and internal standard (IS) (diclofenac) were eluted at 7.4 and 5.4 min, respectively. The limit of quantitation of mefenamic acid in serum was 25 ng/ml at 280 nm. The method was linear over the range of 25-2000 ng/ml with r(2) of 0.998. Mean recovery for mefenamic acid was 110%.

Square-wave adsorptive cathodic stripping voltammetric determination of anti-inflammatory indomethacin drug in tablets and human serum at a mercury electrode

Indomethacin is a non-steroidal anti-inflammatory drug possessing anti-pyretic and analgesic properties. A fully validated square-wave adsorptive cathodic stripping voltammetric procedure is described for determination of indomethacin. The procedure was based on the reduction of the C=O double bond of the drug molecule in Britton-Robinson buffer (pH 4) after its preconcentration onto the mercury electrode surface. The optimized conditions of the procedure were: frequency 120 Hz, scan increment 10 mV, pulse amplitude 50 mV, preconcentration potential -0.9 V (vs. Ag/AgCl/KCl(s)) and preconcentration time 90 s. The proposed procedure was successfully applied for determination of the drug in tablets and human serum with good recoveries. The limits of detection in bulk form and human serum were 6.7 x 10(-10) mol L(-1) and 8.1 x 10(-10) mol L(-1), respectively.

Direct analysis of indomethacin in rat plasma using a column-switching high-performance liquid chromatographic system

We have established a robust, fully automated analytical method for the determination of indomethacin in rat plasma using a column-switching high-performance chromatographic system. The system consists of a precolumn and an analytical column connected in series via a switching valve. When a 50-microl portion of rat plasma containing a therapeutic level of indomethacin was applied directly to the system, the drug was automatically enriched in the precolumn (TSK BSA-ODS) by on-line solid-phase extraction. After elution of the plasma proteins, the analyte was automatically transferred to the analytical column (Zorbax Eclipse XDBC18) where chromatography was performed using isocratic elution and UV absorption detection at a wavelength of 254 nm. The separation mobile phase consisted of methanol-0.1% phosphoric acid (70:30, v/v) at a flow-rate of 1 ml/min. The calibration line for indomethacin showed good linearity in the range 50-10 000 ng/ml (r>0.999) with the detection quantification of 50 ng/ml (RSD=2.6%). Accuracy ranged from -0.62 to 3.22%, and the within- and between-day precision of the assay was better than 6% across the calibration range. The analytical sensitivity and accuracy of this assay is suitable for characterization of the pharmacokinetics of topical administration of imdomethacin to rats. The method has been successfully used to provide pharmacokinetic data in a large number of diverse pharmaceutical studies.

Profiling indomethacin impurities using high-performance liquid chromatography and nuclear magnetic resonance

The anti-inflammatory drug indomethacin was investigated regarding new related impurities. Therefore, related substances 2-9 were prepared by independent synthesis and physicochemically characterized. To determine indomethacin and its related substances, a new HPLC-UV method was developed and validated. Indomethacin and its impurities were eluted on a C(18) column with a mobile phase consisting of methanol and an aqueous solution of 0.2% phosphoric acid at a flow rate of 1.5 ml/min and were quantified by UV detection at 320 nm. Overall, the HPLC-UV method was simple and reliable for the detection of eight impurities in indomethacin. In addition to the HPLC-UV method, 1H nuclear magnetic resonance (NMR) was used to investigate indomethacin regarding impurities. For that purpose, related substances 2-9 were systematically added to indomethacin and investigated. The NMR method was found to be very useful for the identification of impurities in bulk substance without prior separation. Both HPLC-UV and NMR were used to analyze 38 batches of indomethacin available on the European market. The outcome was that 42% of the batches did not meet the compendial requirements although they met the specifications of current compendial methods. Some batches contained the previously undescribed impurity 8, while other batches contained by-products from two distinct synthetic routes. The methods presented herein are important contributions to the ongoing efforts to reduce impurities and therefore the risk of adverse side-effects in drugs that are no longer under patent protection.

Chronobiological variations of indomethacin pharmacokinetic parameters in sheep

A two-phase study to investigate the influence of administration time on pharmacokinetics of indomethacin in sheep was performed. In phase I, 12 animals were allocated to four groups, each corresponding to a different time: 08:00, 14:00, 20:00, 02:00 h. Sheep received an intravenous administration of 1 mg/kg indomethacin. In phase II, each group was administered indomethacin with a 12-h difference compared to Phase I. The trial was performed in autumn, and animals were subjected to a natural light:dark cycle of 10:14 h. Blood samples were taken and processed by high performance liquid chromatography (HPLC) with ultraviolet detection. For each pharmacokinetic parameter, an analysis of variance was performed to outline the existence of chronobiological variations. Concentration at zero time (C0), hybrid constant for distribution and its half life, hybrid constant for elimination and its half-life, volume of distribution (V(d)), area under the curve (AUC(infinity)) and clearance rate (Cl), presented chronobiological variations (P < 0.05) and were fitted to a cosine equation. The following parameters adjusted to circadian rhythms: C(0) (acrophase: 13.9788 h); AUC(infinity) (acrophase: 13.4377 h); V(d) (acrophase: 0.8245 h) and Cl (acrophase: 1.4965 h). It was concluded that pharmacokinetic parameters of intravenously injected indomethacin in sheep would behave in a different, though predictable, manner according to the animal's biological clock.

Indomethacin-loaded methoxy poly(ethylene glycol)/ poly(epsilon-caprolactone) diblock copolymeric nanosphere: pharmacokinetic characteristics of indomethacin in the normal Sprague-Dawley rats

We prepared the drug-loaded polymeric nanospheres composed of the methoxy poly(ethylene glycol) (MePEG) and poly(epsilon-caprolactone) (PCL) that showed a narrow size distribution and average diameter of less than 200 nm. We could obtain the nanosphere having a relatively high drug-loading efficiency of about 42% when the feed weight ratio of indomethacin (IMC) to polymer was 1:1. To investigate the IMC pharmacokinetics in the IMC-loaded MePEG/PCL nanosphere (DMEP70) using the rats as animal model, we analyzed the IMC concentration in plasma with HPLC after i.v. bolus administered at a dose of 10 mg/kg in free IMC (control) and IMC-loaded MePEG/PCL nanosphere (DMEP70) groups via tail vein. Pharmacokinetics parameters (mean +/- s.d.) such as the mean residence time (MRT, h), the steady-state volume of distribution (Vdss, l), the terminal half-time (t 1/2, h) and the plasma clearance (CL, l/h) of IMC in each groups (control vs. DMEP70) were determined; MRT (16.97 +/- 4.83 vs. 28.69 +/- 11.28, p < 0.01); Vdss (14.26 +/- 4.86 vs. 20.37 +/- 12.04, p < 0.05); t 1/2 (15.12 +/- 4.77 vs. 23.1 +/- 8.24, p < 0.01); CL (0.84 +/- 0.27 vs. 0.71 +/- 0.41). From these results, we could concluded that MEP70 has a significant potential for sustained release and the enhancement of circulation time of loaded drug by prolonging terminal half-life, increasing MRT and Vdss of IMC. Therefore, The MePEG/PCL block copolymeric nanosphere system is being considered as promising biodegradable and biocompatible drug carrier vehicles for parentral use and may be useful as sustained release injectable delivery systems for hydrophobic drugs.