Comparative evaluation of polymeric and waxy microspheres for combined colon delivery of ascorbic acid and ketoprofen.

The goal of this work was to combine the ketoprofen anti-inflammatory effect with the ascorbic acid antioxidant properties for a more efficient treatment of colonic pathologies. With this aim, microspheres (MS) based on both waxy materials (ceresine, Precirol(®) and Compritol(®)) or hydrophilic biopolymers (pectine, alginate and chitosan) loaded with the two drugs were developed, physicochemically characterized and compared in terms of entrapment efficiency, in vitro release profiles, potential toxicity and drug permeation properties across the Caco-2 cell line. Waxy MS revealed an high encapsulation efficiency of ketoprofen but a not detectable entrapment of ascorbic acid, while polymeric MS showed a good entrapment efficiency of both drugs. All MS need a gastro-resistant coating, to avoid any premature release of the drugs. Ketoprofen release rate from polymeric matrices was clearly higher than from the waxy ones. In contrast, the ASC release rate was higher, due to its high hydro-solubility. Cytotoxicity studies revealed the safety of all the formulations. Transport studies showed that the ketoprofen apparent permeability increased, when formulated with the different MS. In conclusion, only polymeric MS enabled an efficient double encapsulation of both the hydrophilic and lipophilic drugs, and, in addition, presented higher drug release rate and stronger enhancer properties.

[Preparation of citrulline microspheres by spray drying technique for colonic targeting]. / Préparation des microsphères de citrulline à ciblage colique par la technique de spray drying.

INTRODUCTION: Citrulline is an amino acid that becomes essential in situations of intestinal insufficiency such as short bowel syndrome. It is therefore interesting to provide the patients with dosage forms for routing citrulline to the colon. The aim of this work is to formulate microspheres of citrulline for colonic targeting by the technique of spray drying. MATERIAL AND METHODS: Eudragit(®) FS 30D was selected as polymer to encapsulate citrulline using the spray drying technique. Citrulline and Eudragit(®) FS 30D were dissolved in water and ethanol, respectively. The aqueous and the ethanolic solutions were then mixed in 1:2 (v/v) ratio. Microspheres were obtained by nebulizing the citrulline-Eudragit(®) FS 30D solution using a Mini spray dryer equipped with a 0.7mm nozzle. The microspheres have been formulated using citrulline and Eudragit(®) FS 30D. The size distribution of microspheres was determined by light diffraction. The morphology of the microspheres was studied by electron microscopy. Manufacturing yields, encapsulation rate and dissolution profiles were also studied. RESULTS AND DISCUSSION: The microspheres obtained had a spherical shape with a smooth surface and a homogeneous size except for the microspheres containing the highest concentration of polymer (90 %). The formulation showed that the size and morphology of the microspheres are influenced by the polymer concentration. Manufacturing yields were about 51 % but encapsulation rate were always very high (above 90 %). The in vitro dissolution study showed that the use of the Eudragit(®) FS 30D under these conditions is not appropriate to change the dissolution profile of the citrulline. CONCLUSION: This technique has led to the formulation of microspheres with good physical properties in terms of morphology and size. The compression of the microspheres should help to control citrulline release for colonic targeting.

Influence of cross-linking agent type and chitosan content on the performance of pectinate-chitosan beads aimed for colon-specific drug delivery.

Pectinate-chitosan-beads aimed for colon theophylline delivery have been developed. The effect of zinc or calcium ions as cross-linking agent, and of chitosan concentration on the properties and colon-targeting performance of beads was investigated. Beads were characterized for morphology, entrapment efficiency and mucoadhesion properties. Zn-pectinate-chitosan beads formed a stronger gel network than the Ca-containing ones, enabling a greater entrapment efficiency, which further increased with chitosan content, probably due to polyelectrolyte complexes formation. Transport studies across Caco-2 cells evidenced a significant (p > 0.05) drug permeation increase from all beads with respect to drug alone, attributable to the enhancer and/or mucoadhesion properties of the polymers, and Ca-pectinate-chitosan beads were more effective than the Zn-containing ones. Beads formulated as enteric-coated tablets demonstrated good colon-targeting properties, and no differences were observed in drug-release profiles from Zn- or Ca-pectinate-chitosan beads. Therefore, Ca-pectinate-chitosan beads emerged as the choice formulation, joining colon-targeting specificity with better permeation enhancer power.

Improvement of oxaprozin solubility and permeability by the combined use of cyclodextrin, chitosan, and bile components.

The effect of the combined use of randomly methylated ß-cyclodextrin (RAMEB), chitosan (CS), and bile components (dehydrocholic (DHCA) or ursodeoxycholic (UDCA) acids and their sodium salts) on solubility and permeability through Caco-2 cells of oxaprozin (a very poorly water-soluble non-steroidal anti-inflammatory drug) has been investigated. Addition of CS, bile acids, and their sodium salts increased the RAMEB solubilizing power of 4, 2, and 5 times, respectively. Drug-RAMEB-CS co-ground systems showed very higher dissolution rate than corresponding drug-RAMEB systems. Addition of bile components further improved drug dissolution rate. The CS presence enabled a significant increase in drug permeability through Caco-2 cells with respect to drug-RAMEB systems. Moreover, CS and NaDHC showed a synergistic enhancer effect, enabling a 1.4-fold permeability increase in comparison with systems without bile salt. However, unexpectedly, no significant differences were found between physical mixtures and co-ground products, indicating that drug permeation improvement was due to the intrinsic enhancer effect of the carriers and not to drug-carrier interactions brought about by co-grinding, as instead found in dissolution rate studies. The combined use of RAMEB, CS, and NaDHC could be exploited to develop effective oral dosage forms of oxaprozin, with increased drug solubility and permeability, and then improved bioavailability.

Microspheres for colonic delivery of ketoprofen-hydroxypropyl-beta-cyclodextrin complex.

A new multiparticulate system, with the potential for site-specific delivery to the colon, has been developed using ketoprofen as model drug. The system simultaneously exploits cyclodextrin complexation, to improve drug solubility, and vectorization in microspheres (MS) based on Ca-pectinate and chitosan. The effect of complexation with hydroxypropyl-beta-cyclodextrin (HPbetaCyd) and of chitosan presence on drug entrapment efficiency and release properties, as well on the drug permeation rate across Caco-2 cells has been investigated. Solid-state interactions between the components have been investigated by FTIR spectroscopy, differential scanning calorimetry and X-ray powder diffractometry. The morphology of MS was examined by scanning electron microscopy. Release studies revealed a different behaviour for MS containing drug alone or as complex: drug alone was released faster than in the presence of cyclodextrin from MS without chitosan, due to a reservoir effect. The opposite was found for MS containing chitosan, due to a competition effect between polymer and drug for the cyclodextrin. Cytotoxicity tests demonstrated the safety of these formulations. Permeation studies showed an increased permeation of the drug formulated as MS, particularly marked when it was used as complex, thus revealing an enhancing power of both cyclodextrin and chitosan with a synergistic effect in improving drug permeation.

Influence of cyclodextrins and chitosan, separately or in combination, on glyburide solubility and permeability.

The effect of chitosan and of different concentrations of beta- or hydroxypropyl-beta-cyclodextrins, separately or in various (w/w) combinations, on the dissolution characteristics of glyburide (an oral hypoglycemic agent subject to incomplete and variable bioavailability) and on its permeability through Caco-2 cells has been investigated. Cyclodextrins (and particularly the hydroxypropyl-derivative, in virtue of its higher water solubility) were clearly more effective than chitosan in enhancing the drug dissolution properties: the aqueous glyburide solubility was improved 40-fold in the presence of 25 mM hydroxypropyl-beta-cyclodextrin, 25-fold in the presence of 13 mM beta-cyclodextrin (saturation solubility) and only 3-fold in the presence of chitosan at its saturation concentration (0.5% w/v). When chitosan and cyclodextrin were simultaneously present, a strong reduction of the cyclodextrin solubilizing efficiency towards the drug was observed, and it was attributed to a possible competition effect of polymer and glyburide for the interaction with the macrocycle. By contrast, permeation studies revealed that chitosan was more powerful than cyclodextrins in enhancing the glyburide permeability through Caco-2 cells. This was probably in virtue of the polymer's favourable effect on the tight junctions opening, as demonstrated by the significant decrease in the transepithelial electrical resistance recorded in its presence. Moreover, interestingly, when using the carriers together, conversely from solubility studies, a significant (P < 0.05) synergistic effect in enhancing glyburide apparent permeability was revealed in permeation experiments.

Almost all about citrulline in mammals.

Citrulline (Cit, C6H13N3O3), which is a ubiquitous amino acid in mammals, is strongly related to arginine. Citrulline metabolism in mammals is divided into two fields: free citrulline and citrullinated proteins. Free citrulline metabolism involves three key enzymes: NO synthase (NOS) and ornithine carbamoyltransferase (OCT) which produce citrulline, and argininosuccinate synthetase (ASS) that converts it into argininosuccinate. The tissue distribution of these enzymes distinguishes three "orthogonal" metabolic pathways for citrulline. Firstly, in the liver, citrulline is locally synthesized by OCT and metabolized by ASS for urea production. Secondly, in most of the tissues producing NO, citrulline is recycled into arginine via ASS to increase arginine availability for NO production. Thirdly, citrulline is synthesized in the gut from glutamine (with OCT), released into the blood and converted back into arginine in the kidneys (by ASS); in this pathway, circulating citrulline is in fact a masked form of arginine to avoid liver captation. Each of these pathways has related pathologies and, even more interestingly, citrulline could potentially be used to monitor or treat some of these pathologies. Citrulline has long been administered in the treatment of inherited urea cycle disorders, and recent studies suggest that citrulline may be used to control the production of NO. Recently, citrulline was demonstrated as a potentially useful marker of short bowel function in a wide range of pathologies. One of the most promising research directions deals with the administration of citrulline as a more efficient alternative to arginine, especially against underlying splanchnic sequestration of amino acids. Protein citrullination results from post-translational modification of arginine; that occurs mainly in keratinization-related proteins and myelins, and insufficiencies in this citrullination occur in some auto-immune diseases such as rheumatoid arthritis, psoriasis or multiple sclerosis.

Influence of chitosan and its glutamate and hydrochloride salts on naproxen dissolution rate and permeation across Caco-2 cells.

Chitosan and its glutamate and hydrochloride salts were evaluated for their efficacy in improving the dissolution behaviour of naproxen (a poorly water-soluble antiinflammatory drug) and its transport in vitro across Caco-2 cell monolayers. Drug-polymer physical mixtures and coground products, prepared at two different w/w ratios (30/70 and 10/90), were characterized by differential scanning calorimetry, X-ray powder diffractometry, scanning electron microscopy, and tested for dissolution properties. Coground systems were more effective than physical mixtures in improving drug dissolution and chitosan base, in spite of its lower water solubility, showed higher solubilizing power than its salts. According to the solid state analyses results, this effect was directly related to its stronger amorphizing power. Transport studies showed that only coground mixtures with chitosan glutamate salt allowed a significant drug apparent permeability improvement; however, they did not exhibit appreciable effects on the Caco-2 tight junctions (measured by the trans-epithelial electrical resistance variations), thus indicating that their enhancer effect was mainly due to an improved naproxen transport by transcellular passive diffusion rather than through the paracellular route. The direct compression properties and antiulcerogenic activity together with the demonstrated dissolution and permeation enhancer abilities toward naproxen make chitosan glutamate an optimal carrier for developing fast-action oral solid dosage forms of this drug.

XAS applied to pharmaceuticals: drug administration and bioavailability.

We present selected XAS applications, focused towards practical hospital questions of drug administration and bioavailability, where the technique is driven up to its limits of sensitivity. i) XAS was used to study the interactions between the components of parenteral nutrition solutions, in particular zinc and aminoacids, possibly modifying their bioavailability. ii) We studied by EXAFS a series of binary and ternary copper-aminoacid complexes, in view of the development of an efficient oral drug against copper deficiencies in Menkes disease. iii) EXAFS and XANES analysis allowed us to characterise the solution form of a new arsenic containing drug against leukaemia. In parallel to the XAS measurements, we analysed trace elements levels along patients' hairs, using X-ray fluorescence excited by synchrotron radiation. The measurements along the hair allow for a monitoring of essential trace elements during therapy.

In vitro and in vivo evaluation of carbamazepine-PEG 6000 solid dispersions.

The present work extended previous physico-chemical investigations on the effects of solid dispersion on the solubility, the dissolution rate and the pharmacokinetic profile of carbamazepine. Solubility studies showed a linear increase in carbamazepine solubility with the increase of PEG 6000 concentration. There is no marked difference between physical mixtures and solid dispersions for the enhancement of carbamazepine solubility by PEG 6000. Less than 60% of pure carbamazepine was dissolved in 90 min. Physical mixtures (carbamazepine phase III) and solid dispersions (carbamazepine phase II) dissolution rates were higher in comparison of the parent drug. The dissolution of carbamazepine phase III was more pronounced than that evoked by the phase II. The dissolution profiles indicated that the percentage of the drug dissolved was dependent on the proportion of PEG 6000. In solid dispersions there was a remarkable enhancement in the dissolution rates of the drug in the vicinity of the eutectic composition as compared with those of corresponding physical mixtures. Hence, the optimum value for the solid dispersion was 80.5+/-1.7% of carbamazepine having dissolved within the first 10 min compared to 40+/-1% for the corresponding physical mixtures of the same composition. Statistical analysis of pharmacokinetic parameters confirmed that the carbamazepine:PEG 6000 binary systems displayed higher bioavailability of the drug than the pure carbamazepine. The area under the curve (AUC) values highlighted the evidence that only slight differences in the bioavailability of the drug occur between physical mixtures and solid dispersions prepared at the 80:20 and 50:50 drug:carrier compositions. However, the mean normalized plasma concentrations showed that standard error deviations are rather wide intervals for pure drug and physical mixtures in comparison to solid dispersions. One additional interesting point to consider is the disappearance of the multiple peaks on the individual kinetic curves of the 50:50 solid dispersion composition. Furthermore, our investigations have highlighted the interest of solid dispersions prepared at <>-eutectic composition as our preliminary data show that the plasma concentration (C(5h)) of the drug for the 15:85 dispersed sample containing 150 mg of carbamazepine is not significantly different from that obtained for the 50:50 dispersed sample containing 300 mg of the drug.

Audit of ketoprofen prescribing after orthopedic and general surgery.

PURPOSE: In 1994, we developed a practice guideline which stated that ketoprofen should be used in every adult patient after surgical procedures for which at least moderate pain was anticipated. The dose recommended was 50 mg every six hours i.v. in the operating room followed by oral administration as soon as possible for three days. The purpose of this study was to evaluate the success of the guideline implementation. METHODS: In 1995, an audit performed by a research pharmacist assistant under the supervision of the authors analysed prospectively the files of patients scheduled for orthopedic or general surgery during a one-month period. The compliance of the nurses was also recorded. RESULTS: Of 185 patients operated upon during the period, seven were transferred to the ICU and were not evaluated. Ketoprofen was not prescribed to 112 (63%) of the 177 remaining patients, either because minor pain was expected (n = 55) or because one or several contra-indications to its use were detected. In cases where ketoprofen was used although theoretically contraindicated (11%), review of the medical records and interviews of anesthesiologists showed that prescription was guided by a risk/benefit analysis. In 18% of cases, nurses did not administer at least one dose of ketoprofen although medical prescription requested regular administration. CONCLUSION: Although the use of NSAIDs is still controversial, implementation by anesthesiologists of a practice guideline introducing ketoprofen for postoperative analgesia was successful and the nursing non-compliance rate to follow written orders was modest.

Comparison between conventional axillary block and a new approach at the midhumeral level.

We undertook this prospective, randomized study to compare the success rate, time spent performing the blocks, onset time of surgical anesthesia, presence of complete motor blockade, and lidocaine plasma concentrations between conventional axillary block and a new approach at the midhumeral level. Both techniques were performed using a peripheral nerve stimulator. Two nerves were located at the axillary crease, whereas four nerves were located at the midhumeral level. Sixty patients undergoing upper limb surgery were assigned to one of the two techniques. The sensory block was evaluated before surgery for all of the distributions of the four major nerves of the upper extremity. A subset of patients had lidocaine plasma concentrations determined. Times to perform the blocks, mean maximum plasma lidocaine concentration, and time to peak concentration were not different between groups. The success rate of the block, as well as the incidence of complete motor blockade, was greater with the midhumeral approach compared with the axillary approach. However, the onset time to complete anesthesia of the upper extremity was shorter in the axillary approach. For brachial plexus anesthesia, we conclude that the midhumeral approach provided a greater success rate than the traditional axillary approach.