紫杉醇自组装核壳型纳米胶束的制备与性能

本文合成了聚乙二醇-聚谷氨酸苄酯(polyethylene glycol-polybenzyl-L-glutamate， PEG-PBLG)两亲嵌段共聚物， 并采用超微透析法制备了紫杉醇/PEG-PBLG核壳型纳米胶束。通过高效液相色谱测定了胶束的载药量及药物包封率； 采用动态光散射法测定了胶束的粒径及分布； 通过体外试验研究了紫杉醇/PEG-PBLG胶束的释药特性； 采用四噻唑蓝法考察了紫杉醇/PEG-PBLG胶束的体外细胞毒性； 通过裸鼠的抑瘤试验评价了紫杉醇胶束对人肝癌细胞的疗效。结果表明， PEG-PBLG胶束能包埋疏水性药物紫杉醇； 紫杉醇/PEG-PBLG胶束的粒径为80～265 nm， 且随着载体共聚物PBLG嵌段相对分子质量的升高而增大； 紫杉醇/PEG-PBLG胶束的体外释放具有缓释特性； 当紫杉醇浓度大于20 μg·mL^-1时， 紫杉醇/PEG-PBLG胶束的细胞毒性低于相应浓度的紫杉醇/聚氧乙烯蓖麻油注射剂(P<0.05)， 紫杉醇/PEG-PBLG胶束具有与紫杉醇/聚氧乙烯蓖麻油注射剂相似的抑制肿瘤作用。综上所述， 紫杉醇/PEG-PBLG纳米胶束具有较均匀的粒径及粒径分布、 缓释特性、 低毒和较好的抗肿瘤作用。     

Distribution of paclitaxel in plasma and cerebrospinal fluid

Our objective was to assess the distribution of paclitaxel in plasma and cerebrospinal fluid (CSF) in a cancer patient, and evaluate the role of the formulation vehicle Cremophor EL (CrEL) in drug distribution. Analysis of paclitaxel concentrations in CSF was performed using a triple-quadrupole mass spectrometric assay with electrospray ionization. Total and unbound paclitaxel levels in plasma were measured by liquid chromatography and equilibrium dialysis, respectively, and CrEL concentrations were determined by a colorimetric dye-binding microassay. Clinical samples were obtained from a 54-year-old female with breast cancer receiving a weekly regimen of paclitaxel (dose 60 mg/m2). The disposition of total paclitaxel in plasma was characterized by a bi-exponential elimination (terminal half-life 9.17 h) and a total clearance of 19.4 l/h/m2. The fraction of unbound paclitaxel in plasma ranged from 7.6 to 12.4% (unbound drug CL 176 l/h/m2). The plasma clearance of CrEL was 0.332 l/h/m2, whereas CrEL levels were undetectable in CSF (below 0.5 microl/ml). Concentrations of paclitaxel in CSF (range 45.5-162 pg/ml) and unbound CSF:unbound plasma concentration ratios (range 0.093-9.53%) progressively increased up to 24 h, with a mean unbound drug fraction in CSF of 84+/-3.6% (range 81-88%). These findings indicate that there is substantial distribution of paclitaxel to CSF. Since the fraction of unbound paclitaxel is different between plasma and CSF, measurement of unbound paclitaxel is required to accurately assess the extent of drug penetration.     

Pharmacokinetics and pharmacodynamics of combination chemotherapy with paclitaxel and epirubicin in breast cancer patients

AIMS: To investigate the pharmacokinetics and pharmacodynamics of epirubicin and paclitaxel in combination, as well as the effects of paclitaxel and its vehicle Cremophor EL on epirubicin metabolism. METHODS: Twenty-seven female patients with metastatic breast cancer received epirubicin 90 mg m-2 i.v. followed 15 min or 30 h later by a 3 h i.v. infusion of paclitaxel 175, 200 and 225 mg m-2. Plasma concentrations of paclitaxel, epirubicin and epirubicinol were measured and the relationship between neutropenia and drug pharmacokinetics was evaluated using a sigmoid maximum effect (Emax) model. Finally, the influence of paclitaxel and Cremophor EL on epirubicin metabolism by whole blood was examined. RESULTS: An increase in epirubicinol plasma concentrations occurred after the start of the paclitaxel infusion, resulting in a significant increase in the area under the plasma concentration-time curve (AUC) of epirubicinol (+0.5 micromol l-1 h [95% CI for the difference: 0.29, 0.71],+0.66 micromol l-1 h [95% CI for the difference: 0.47, 0.85] and +0.82 micromol l-1 h [95% CI for the difference: 0.53, 1.11] at paclitaxel doses of 175, 200 and 225 mg m-2, respectively), compared with epirubicin followed by paclitaxel 30 h later (0.61+/-0.1 micromol l-1 h). A significant increase in epirubicin AUC (+0.74 micromol l-1 h [95% CI for the difference: 0.14, 1.34] and +1.09 micromol l-1 h [95% CI for the difference: 0.44, 1.74]) and decrease in drug clearance (CLTB) (-25.35 l h-1 m-2[95% CI for the difference: -50.18, -0.52] and -35.9 l h-1 m-2[95% CI for the difference -63,4,-8,36]) occurred in combination with paclitaxel 200 and 225 mg m-2 with respect to the AUC (3.16+/-0.6 micromol l-1 h) and CLTB (74.4+/-28.4 l h-1 m-2) of epirubicin followed by paclitaxel 30 h later. An Emax relationship was observed between neutropaenia and the time over which paclitaxel plasma concentrations were equal to or greater than 0.1 micromol l-1 (tC0.1). The tC0.1 value predicted to yield a 50% decrease in neutrophil count was 7.7 h. Finally, Cremophor EL markedly inhibited the metabolism of epirubicin to epirubicinol in whole blood. CONCLUSIONS: Paclitaxel/Cremophor EL affects the disposition of epirubicinol and epirubicin. Furthermore, the slope factor of the Emax relationship between neutropenia and tC0.1 of paclitaxel suggests that the drugs might also interact at the pharmacodynamic level.     

Preclinical evaluation of alternative pharmaceutical delivery vehicles for paclitaxel

New solubilizers, including Sorporol 230, Sorporol 120Ex, Aceporol 345-T, Aceporol 460 and Riciporol 335, as potential new delivery vehicles for paclitaxel were investigated, since recent studies have shown that the paclitaxel delivery vehicle Cremophor EL significantly alters the pharmacokinetics of paclitaxel. Cremophor EL and Tween 80 were used as a reference. As in the case of Cremophor EL, alteration of blood distribution of paclitaxel occurred in the presence of all tested vehicles. Also, no differences in the affinity of paclitaxel for the tested solubilizers was found during equilibrium dialysis experiments. The different vehicles could be distinguished by a different rate of esterase-mediated breakdown, which was correlated with the fatty acid content of the solubilizers. The activation of the complement cascade was less pronounced for all solubilizers, except Riciporol 335, compared to Cremophor EL. The strategies presented here provide the possibility to rapidly screen future candidate delivery vehicles with optimal characteristics for use as a solubilizer in clinical formulations of paclitaxel or other poorly water-soluble drugs.     

Disposition of [G-(3)H]paclitaxel and cremophor EL in a patient with severely impaired renal function.

In the present work, we studied the pharmacokinetics and metabolic disposition of [G-(3)H]paclitaxel in a female patient with recurrent ovarian cancer and severe renal impairment (creatinine clearance: approximately 20 ml/min) due to chronic hypertension and prior cisplatin treatment. During six 3-weekly courses of paclitaxel at a dose level of 157.5 mg/m(2) (viz. a 10% dose reduction), the renal function remained stable. Pharmacokinetic evaluation revealed a reproducible and surprisingly high paclitaxel area under the plasma concentration-time curve of 26.0 +/- 1.11 microM.h (mean +/- S.D.; n = 6; c.v. = 4.29%), and a terminal disposition half-life of approximately 29 h. Both parameters are substantially increased ( approximately 1.5-fold) when compared with kinetic data obtained from patients with normal renal function. The cumulative urinary excretion of the parent drug was consistently low and averaged 1.58 +/- 0.417% (+/- S.D.) of the dose. Total fecal excretion (measured in one course) was 52.9% of the delivered radioactivity, and mainly comprised known mono- and dihydroxylated metabolites, with unchanged paclitaxel accounting for only 6.18%. The plasma area under the plasma concentration-time curve of the paclitaxel vehicle Cremophor EL, which can profoundly alter the kinetics of paclitaxel, was 114.9 +/- 5.39 microl.h/ml, and not different from historic data in patients with normal or mild renal dysfunction. Urinary excretion of Cremophor EL was less than 0.1% of the total amount administered. These data indicate that the substantial increase in systemic exposure of the patient to paclitaxel relates to decreased renal metabolism and/or urinary elimination of polar radioactive species, most likely lacking an intact taxane ring fragment.     

紫杉醇新型制剂及临床研究进展

紫杉醇是一种临床应用广泛的广谱抗肿瘤药物,其独特的阻碍微管蛋白解聚的作用机制使其对多种实体瘤具有良好的疗效。但由于紫杉醇的水溶性极低,早期上市的传统制剂采用了高浓度的聚氧乙烯蓖麻油(Cremophor EL)作为增溶剂,后者易引发一系列过敏反应,用药前需进行脱敏处理,严重限制了紫杉醇的临床使用,同时给患者带来极大的痛苦。不含Cremophor EL的紫杉醇新制剂的开发多年来持续受到国内外的广泛关注,其中成功上市的有紫杉醇脂质体(力扑素~)、注射用白蛋白结合型紫杉醇(Abraxane~)和紫杉醇聚合物胶束Genexol~-PM,进入Ⅰ~Ⅲ期临床研究的有脂质体LEP-ETU、阳离子脂质体EndoTAG~-1、胶束化纳米粒NK105和新型口服制剂DHP107。本文对上述新型制剂的特点及临床研究进展进行回顾和综述。     

Cremophor EL pharmacokinetics in a phase I study of paclitaxel (Taxol) and carboplatin in non-small cell lung cancer patients

The purpose of our study was to investigate the pharmacokinetics of Cremophor EL following administration of escalating doses of Taxol (paclitaxel dissolved in Cremophor EL/ethanol) to non-small cell lung cancer (NSCLC) patients. Patients with NSCLC stage IIIb or IV without prior chemotherapy treatment were eligible for treatment with paclitaxel and carboplatin in a dose-finding phase I study. The starting dose of paclitaxel was 100 mg/m2 and doses were escalated with steps of 25 mg/m2, which is equal to a starting dose of Cremophor EL of 8.3 ml/m2 with dose increments of 2.1 ml/m2. Carboplatin dosages were 300, 350 or 400 mg/m2. Pharmacokinetic sampling was performed during the first and the second course, and the samples were analyzed using a validated high-performance liquid chromatographic assay. A total of 39 patients were included in this pharmacokinetic part of the study. The doses of paclitaxel were escalated up to 250 mg/m2 (20.8 ml/m2 Cremophor EL). Pharmacokinetic analyses revealed a low elimination-rate of Cremophor EL (CI=37.8-134 ml/h/m2; t 1/2=34.4-61.5 h) and a volume of distribution similar to the volume of the central blood compartment (Vss=4.96-7.85 l). In addition, a dose-independent clearance of Cremophor EL was found indicating linear kinetics. Dose adjustment using the body surface area, however, resulted in a non-linear increase in systemic exposure. The use of body surface area in calculations of Cremophor EL should therefore be re-evaluated.     

Effect of unpurified Cremophor EL on the solution stability of paclitaxel

Taxol for Injection Concentrate contains a solution of paclitaxel in a 50:50 v/v mixture of Cremophor EL (cleaned):ethanol. Cleaned, rather than unpurified, Cremophor EL is used as a cosolvent because paclitaxel was observed to be less stable in the presence of unpurified Cremophor. In order to understand the cause of this paclitaxel instability, various studies were performed. The results of these studies, coupled with the examination of degradation products, suggested that carboxylate anions present in the unpurified Cremophor catalyze the degradation of paclitaxel by general base catalyzed ethanolysis. Stabilization of Taxol for Injection Concentrate prepared with unpurified Cremophor can be achieved by addition of strong acids, resulting in neutralization of the carboxylate anions. Separately, a quality control test for the cleaning procedure of Cremophor is needed to insure stability of Taxol for Injection Concentrate. A colorimetric indicator test was identified which can distinguish between good and poor quality cleaned Cremophor as it pertains to paclitaxel stability.     

Paclitaxel pharmacodynamics: application of a mechanism-based neutropenia model.

Antineoplastic agents exert adverse effects that impact both dose and scheduling of drug administration. Our objective was to develop a quantitative relationship between paclitaxel (taxol) exposure and pharmacodynamic endpoints, such as neutropenia or body weight loss. Paclitaxel in liposomes or Cremophor EL was administered to rats at doses of 20 or 40 mg/kg. Body weight and absolute neutrophil count were determined daily. The decrease in body weight was greater for paclitaxel in Cremophor EL than for liposomal paclitaxel, but hematological toxicity was similar. The hematological data was fit using a pharmacodynamic model to investigate the temporal delay between drug exposure and neutropenia. From the model, the lifespan of neutrophils (T(N)), of surviving precursor cells in bone marrow (T(P)), and a killing rate constant (K) were determined. The values of T(N), T(P), and K for liposomal paclitaxel were 95 h, 82 h, and 0.735 (microM h)(-1), respectively, and for paclitaxel in Cremophor EL, 86 h, 78 h, and 0.475 (microM h)(-1), respectively. Simulations of various doses indicated a dependency of the neutropenia time course on paclitaxel exposure. The entire time course of changes in neutrophil count is more informative than a single measurement if myelosuppression is prolonged and at a level associated with increased incidence of clinical adverse effects.     

Enhanced oral bioavailability of paclitaxel by D-alpha-tocopheryl polyethylene glycol 400 succinate in mice

Paclitaxel is widely used to treat several types of solid tumors. The commercially available paclitaxel formulation contains Cremophor/ethanol as solubilizers. This study evaluated the effects of D-alpha-tocopheryl polyethylene glycol 400 succinate (TPGS 400) on the oral absorption of paclitaxel in mice. Mice were given an intravenous (18mg/kg) or oral (100mg/kg) dose of paclitaxel solubilized in Cremophor/ethanol or in TPGS 400/ethanol formulations. Paclitaxel plasma concentrations and pharmacokinetic parameters were determined. The maximal plasma concentrations of paclitaxel after an oral dose were 1.77+/-0.17 and 3.39+/-0.49microg/ml for Cremophor/ethanol and TPGS 400/ethanol formulations, respectively, with a similar time at 40-47min to reach the maximal plasma concentrations. The oral bioavailability of paclitaxel in TPGS 400/ethanol (7.8%) was 3-fold higher than that in Cremophor/ethanol (2.5%). On the other hand, the plasma pharmacokinetic profiles of intravenous paclitaxel demonstrated a superimposition for the two formulations. Furthermore, TPGS 400 concentration-dependently increased the intracellular retention of Rhodamine 123 in Caco-2 cells and enhanced paclitaxel permeability in monolayer Caco-2 cultures. TPGS 400 at concentrations up to 1mM did not inhibit testosterone 6beta-hydroxylase, a cytochrome P450 isozyme 3A in liver microsomes metabolizing paclitaxel. Our results indicated that TPGS 400 enhances the oral bioavailability of paclitaxel in mice and the enhancement may result from an increase in intestinal absorption of paclitaxel.     

Role of Formulation Vehicles in Taxane Pharmacology

The non-ionic surfactants Cremophor EL (CrEL) and Tween 80,both used as formulation vehicles of many (anticancer) agentsincluding paclitaxel and docetaxel, are not physiologicalinert compounds. We describe their biological properties,especially the toxic side effects, and their pharmacologicalproperties, such as modulation of P-glycoprotein activity. Indetail, we discuss their influence on the disposition of thesolubilized drugs, with focus on CrEL and paclitaxel, and ofconcomitantly administered drugs. The ability of thesurfactants to form micelles in aqueous solution as well asbiological fluids (e.g. plasma) appears to be of greatimportance with respect to the pharmacokinetic behavior of theformulated drugs. Due to drug entrapment in the micelles,plasma concentrations and clearance of free drug changesignificant leading to alteration in pharmacodynamiccharacteristics. We conclude with some perspectives related tofurther investigation and development of alternative methodsof administration.     

Preparation and evaluation of Cremophor-free paclitaxel solid dispersion by a supercritical antisolvent process

Objectives To avoid the major adverse effects induced by Cremophor EL formulated in the commercial paclitaxel products of Taxol. Methods An injectable paclitaxel solid dispersion free of Cremophor was prepared by a supercritical antisolvent process and then was fully characterized and investigated with regard to its short‐term and long‐term stability. Pharmacokinetics in rats was also evaluated compared with the commercial product. Key findings The solid dispersion system at a 1/20/40 weight ratio of paclitaxel/HP‐β‐CD/HCO‐40 had a paclitaxel solubility of about 10 mg/ml, an almost 10 000‐fold increase over its aqueous solubility. This system was physically stable for at least six months or four weeks in accelerated conditions (40 ± 2°C; RH: 75 ± 5%) and stress conditions (60°C), respectively. The precipitation time of paclitaxel solid dispersion in 0.9% sodium chloride injection at a concentration of 1000 µg/ml was above 70 h at room temperature. Intravenous administration of paclitaxel solid dispersion at a dose of 6 mg/kg revealed no significant differences when compared with the commercial product. However, our results obtained at a dose of 12 mg/kg showed a striking non‐linear increase in the plasma Cmax and AUCall with increased dose. In addition, the concentrations of paclitaxel in various organs in the solid dispersion group were found to be higher than those of Taxol at 6 mg/kg, and the paclitaxel levels in these organs increased proportionately with increasing dose. Conclusions Nano‐scale paclitaxel solid dispersion without Cremophor EL provided advantageous results over Taxol with respect to the physicochemical properties, safety, clinic convenience and pharmacokinetic behaviour in rats.     

Pharmacokinetic modeling of the blood‐stable camptothecin analog AR‐67 in two different formulations

AR‐67 is a lipophilic camptothecin analog currently under clinical investigation using a Cremophor EL based formulation. However, as potential toxicity limitations exist in the clinical use of Cremophor, an alternative cyclodextrin (SBE‐β‐CD) based formulation has been proposed. Pharmacokinetic (PK) studies were conducted in mice and the SBE‐β‐CD based formulation was compared with the Cremophor EL formulation. PK studies were conducted following intravenous or oral administration of AR‐67 in either Cremophor or SBE‐β‐CD formulation in mice. Noncompartmental analysis was used to determine the plasma and tissue drug distribution. A non‐linear mixed effects (population) PK model was developed to fit both the oral and intravenous data and to estimate key PK parameters. The effect of formulation was explored as a covariate in the PK model. AR‐67 in the SBE‐β‐CD formulation had similar plasma PK and biodistribution to that in the Cremophor EL formulation. The proposed two‐compartment model described the plasma PK of AR‐67 in both formulations adequately. AR‐67 in the SBE‐β‐CD formulation exhibited dose linearity following both oral and intravenous administration. Our studies indicate that SBE‐β‐CD is a viable alternative to Cremophor EL as a pharmaceutical excipient for formulating AR‐67.     

Localized delivery of paclitaxel using elastic liposomes: formulation development and evaluation

In the present study an elastic liposomes-based paclitaxel formulation was developed with the objective to remove Cremophor EL. Cremophor EL is currently used for solubilizing paclitaxel in the marketed formulation and is known to produce toxic effects. Elastic liposomal paclitaxel formulation was extensively characterized in vitro, ex-vivo, and in vivo. The results obtained were compared against the marketed paclitaxel formulation. The maximum amount of paclitaxel loaded in the elastic liposomal formulation was found to be 6.0 mg/ml, which is similar to the commercial strength of marketed paclitaxel formulation. In vitro skin permeation and deposition studies showed 10.8-fold enhanced steady state transdermal flux and 15.0-fold enhanced drug deposition in comparison to drug solution. These results further confirmed with the vesicle-skin interaction study using FTIR technique. Results of the hemolytic toxicity assay indicate that elastic liposomal formulation induced only 11.2 ± 0.2% hemolysis in comparison to the commercial formulation which showed 38 ± 3.0%. Further, results of the Draize test showed no skin irritation of paclitaxel elastic liposomal formulation. Findings of the study demonstrate that elastic liposomes as a carrier is an attractive approach for localized delivery of paclitaxel.     

Localized delivery of paclitaxel using elastic liposomes: Formulation development and evaluation

In the present study an elastic liposomes-based paclitaxel formulation was developed with the objective to remove Cremophor EL. Cremophor EL is currently used for solubilizing paclitaxel in the marketed formulation and is known to produce toxic effects. Elastic liposomal paclitaxel formulation was extensively characterized in vitro, ex-vivo, and in vivo. The results obtained were compared against the marketed paclitaxel formulation. The maximum amount of paclitaxel loaded in the elastic liposomal formulation was found to be 6.0?mg/ml, which is similar to the commercial strength of marketed paclitaxel formulation. In vitro skin permeation and deposition studies showed 10.8-fold enhanced steady state transdermal flux and 15.0-fold enhanced drug deposition in comparison to drug solution. These results further confirmed with the vesicle–skin interaction study using FTIR technique. Results of the hemolytic toxicity assay indicate that elastic liposomal formulation induced only 11.2?±?0.2% hemolysis in comparison to the commercial formulation which showed 38?±?3.0%. Further, results of the Draize test showed no skin irritation of paclitaxel elastic liposomal formulation. Findings of the study demonstrate that elastic liposomes as a carrier is an attractive approach for localized delivery of paclitaxel.     

Pharmacokinetics, tissue distribution and anti-tumour efficacy of paclitaxel delivered by polyvinylpyrrolidone solid dispersion

Objectives Paclitaxel is a potent anti‐cancer drug that has exhibited clinical activity against several tumours. Unfortunately, serious side effects are associated with Taxol, the commercial formulation of paclitaxel, which contains Cremophor EL (CrEL). Currently, the main focus of developing paclitaxel formulations is on improving efficacy and reducing toxicity. A novel, Cremophor‐free, paclitaxel solid dispersion (PSD) was prepared in our laboratory previously. The primary aim of this study was to evaluate the pharmacokinetics, tissue distribution, acute toxicity and anti‐tumour efficacy of the PSD compared with Taxol. Methods SD rats were used to examine the pharmacokinetics and tissue distribution of PSD. The acute toxicity of PSD was evaluated in ICR mouse. The anti‐tumor activity of PSD was assessed in an in vivo anti‐tumor nude mice model inoculated with human SKOV‐3 cancer cells. Key findings The two formulations presented different pharmacokinetic behaviour. The plasma AUC of paclitaxel in the PSD was 5.84‐fold lower than that of Taxol, and the mean residence time, total body clearance and apparent volume of distribution of paclitaxel in the PSD were increased by 1.73, 4.67 and 8.57 fold, respectively. However, the two formulations showed similar tissue distribution properties. CrEL, the vehicle in Taxol, decreased the clearance of paclitaxel from plasma. The LD50 (median lethal dose) was 34.8 mg/kg for Taxol, whereas no death was observed at 160 mg/kg for the PSD. The anti‐tumour activity of PSD was similar to that of Taxol at a dose of 15 mg/kg. Most importantly, the improved tolerance of PSD enabled a higher administrable dose of paclitaxel, which resulted in improved efficacy compared with Taxol administered at its maximum tolerated dose. Conclusions These results suggest that the PSD, a CrEL‐free formulation, is a promising approach to increase the safety and efficacy of paclitaxel.     

Preparation and evaluation of paclitaxel-containing liposomes

Paclitaxel, an antitumoral drug, is poorly soluble in aqueous media. Therefore, in a commercialised formulation (Taxol), paclitaxel (30 mg active compound) is dissolved in polyethoxylated castor oil (Cremophor EL) and ethanol. After dilution of Taxol in aqueous media paclitaxel tends to precipitate. Several side effects, attributed to the surfactant Cremophor EL, occur, e.g. bronchospasm, hypotension, neuro- and nephrotoxicity, and anaphylactic reactions. To eliminate these side effects, the solubility of paclitaxel was enhanced using liposomes instead of Cremophor EL. The amount of entrapped paclitaxel in crystal-free liposomes was 0.5 mg/ml liposome suspension, i.e. almost 85 times the native solubility. Thus, 30 mg paclitaxel had to be dissolved in 60 ml liposome suspension, of either multi-lamellar vesicles (MLV's) or of small unilamellar vesicles (SUV's) with 5% sucrose as cryoprotector. No precipitation was observed after dilution of the MLV-formulation with (physiological) water or with 5% aqueous dextrose solution, which proves their suitability for administration with perfusions. The chemical stability of paclitaxel in the prepared MLV's stored at 4 degrees C was demonstrated during a period of 5 months. The chemical degradation to conjugated dienes and hydroperoxides, two oxidative degradation products of EPC, was negligible (less than 1%).     

Titrimetric determination of Cremophor EL in aqueous solutions and biofluids: part 2: ruggedness of the method with respect to biofluids

A titration method for Cremophor EL, as a multicomponent mixture commonly used as non-ionic emulgent for manufacturing certain parenteralia, was developed for quantitative routine analysis in biofluids. A coated wire electrode is used as the end-point indicator in potentiometric titrations of Cremophor EL with sodium tetraphenylborate. The method tolerates a broad pH range, addition of alkanols and components of drug formulations and is sufficiently rugged. Reliable results are obtained at 20 degrees C. Disturbing ions from biofluid matrices can be masked or complexed by addition of formaldehyde, ethylenediaminetetraacetic acid and sodium fluoride. Sodium hydroxide is used for the required adjustment of the samples to pH 10. Cremophor EL spiked urine samples can be determined directly, whereas the true value of the emulgent content in the case of Cremophor EL spiked plasma samples is achieved by means of a conventional method.     

Preparation and characterization of polymeric pH-sensitive STEALTH® nanoparticles for tumor delivery of a lipophilic prodrug of paclitaxel

Paclitaxel is an effective and widely used anti-cancer agent. However, the drug is difficult to formulate for parenteral administration because of its low water solubility and Cremophor EL, the expient used for its formulation, has been shown to cause serious side effects. The present study reports an alternative administration vehicle involving a lipophilic paclitaxel prodrug, paclitaxel oleate, incorporated in the core of a nanoparticle-based dosage form. A hydrophobic poly (β-amino ester) (PbAE) was used to formulate the nanoparticles, which were stabilized with a mixture of phosphatidylcholine, Synperonic? F 108, and poly(ethylene glycol)-dipalmitoyl phosphatidyl ethanolamine. PbAE undergoes rapid dissolution when the pH of the medium is less than 6.5 and is expected to rapidly release its content within the acidic tumor microenvironment and endo/lysosome compartments of cancer cells. PbAE nanoparticles were prepared by an ultrasonication method and characterized for particle size and physical stability. The nanoparticles obtained had a diameter of about 70 nm and a good physical stability when stored at 4 °C. In vitro cellular uptake and release of paclitaxel oleate PbAE nanoparticles were studied in Jurkat acute lymphoblastic leukemia cells. The results were compared with pclitaxel oleate in poly(?-caprolactone) (PCL) particles, that do not display pH-sensitive release behavior, and paclitaxel in PbAE particles. Both uptake and release of the prodrug were faster when administered in PbAE than in PCL, but much slower than those of the free drug in PbAE. Cytotoxicity assay was performed on the formulations at different doses. Paclitaxel and paclitaxel oleate showed almost identical activity, IC50 123 and 128 nM, respectively, while that of the prodrug in PCL was much lower with IC50 at 2.5 μM. Thus, PbAE nanoparticles with the incorporated paclitaxel prodrug paclitaxel oleate may prove useful for replacement of the toxic Cremophor EL and also by improving the distribution of the drug to the tumor.