Chitosan capsules for colon-specific drug delivery: enhanced localization of 5-aminosalicylic acid in the large intestine accelerates healing of TNBS-induced colitis in rats.

The objective of this study was to achieve the colon-specific delivery of an anti-ulcerative colitis drug using chitosan capsules and to accelerate healing of 2,4,6-trinitrobenzene sulfonic acid sodium salt (TNBS)-induced colitis in rats. 5-Aminosalicylic acid (5-ASA) was used as a model of an anti-inflammatory drug. The gastrointestinal transit of chitosan capsules was determined by counting the number of capsules in the gastrointestinal lumen by celiotomy at certain times after their oral administration to rats. The chitosan capsules reached the large intestine 3.5 h after oral administration in rats. We studied the release of 5-ASA from chitosan capsule by the Japan Pharmacopoeia (JP) rotating basket method. The release of 5-ASA from the chitosan capsule markedly increased in the presence of rat cecal contents. After oral administration of chitosan capsules containing 5-ASA, the concentrations of 5-ASA in the large intestinal mucosa were higher than those in the CMC suspension. For the treatment of colitis in rats, 5-ASA was orally administered using chitosan capsules or a carboxy methyl cellulose (CMC) suspension to TNBS-induced rats. The colonic injury and inflammation were assessed by measuring the myeloperoxidase (MPO) activities, colon wet weight/body weight (C/B) ratio and the damage score, respectively. When 5-ASA was orally administered using chitosan capsules in TNBS-induced colitis rats, we found better therapeutic effects with 5-ASA than with a 5-ASA CMC suspension, as evaluated by the MPO activities, C/B ratio and the damage score. In conclusion, chitosan capsules may be useful carriers for the colon-specific delivery of anti-inflammatory drugs including 5-ASA and the healing of TNBS-induced colitis in rats.     

In vivo therapeutic efficacies of PD 138312 and PD 140248, two novel fluoronaphthyridines with outstanding gram-positive potency.

PD 138312 and PD 140248 are novel broad-spectrum 7-pyrrolidinyl fluoronaphthyridines with a cyclopropyl or a difluorophenyl substitution at the 1 positions, respectively. They have been demonstrated to have excellent in vitro activity against gram-positive organisms. These compounds were evaluated for their in vivo potencies against acute systemic infections in mice and in a mouse pneumococcal pneumonia model. They were very effective by both the oral and subcutaneous routes of administration. Most remarkable were their comparative median protective values against methicillin-resistant Staphylococcus aureus, Streptococcus pneumoniae, and Streptococcus pyogenes. In general, these compounds were 28- to 100-fold more active than ciprofloxacin against these clinically significant organisms when the drugs were given orally and 10- to 38-fold more active when the drugs were given parenterally. Average ratios of drug concentrations in mice after drug administration by the oral route to that after administration by the subcutaneous route indicate 34 to 44% greater bioavailabilities of PD 138312 and PD 140248 compared with that of ciprofloxacin. In a multidose pneumococcal mouse pneumonia model these new quinolones were extremely effective, with median curative doses of 2 to 2.8 mg/kg of body weight per dose. Ciprofloxacin was ineffective (median curative dose, >100 mg/kg per dose) in this model. Comparative pharmacokinetic studies in mice revealed a relative superiority of PD 140248. Peak levels of PD 140248 in blood after the administration of a single oral 50-mg/kg dose were twice those of PD 138312 and ciprofloxacin, with PD 140248 having a substantially longer half-life. These results indicate that PD 138312 and PD 140248 have excellent therapeutic potential against clinically important gram-positive pathogens when the drugs are administered both orally and parenterally.     

Comparison of monomeric and oligomeric transferrin as potential carrier in oral delivery of protein drugs.

Oligomeric transferrin (Tf) was used to investigate the effect that cross-linking of transferrin receptors (TfR) has on intracellular trafficking of the Tf-TfR complex and to determine whether or not the Tf-oligomer would be a better carrier than monomeric Tf for the oral delivery of protein drugs. The intracellular retention and transcytosis of the Tf-oligomer was determined by performing pulse chase studies on enterocyte-like Caco-2 cells. The intracellular retention of the Tf-oligomer was 2-fold higher than that of monomeric Tf while there was no significant difference in transcytosis. However, in vivo studies in CF-1 mice showed that the plasma concentrations of Tf from the orally administered Tf-oligomer were approximately 2-, 3- and 60-fold higher than that of orally administered monomeric Tf at 24, 48 and 72 h post-administration, respectively. In addition, the retention of the Tf-oligomer in the intestine was higher than that of monomeric Tf, which was consistent with in vitro studies. Insulin (In), when conjugated to the Tf-oligomer (Agg-Tf-S-S-In), was more effective than monomeric Tf-In conjugate (Mono-Tf-S-S-In) in reducing blood glucose levels when orally administered to streptozotocin (STZ)-induced diabetic rats. Post-oral administration of Agg-Tf-In, a delayed onset and prolonged hypoglycemic effect was observed. These results demonstrate that the cross-linking of TfR induced by the binding of the oligomeric Tf alters the intracellular trafficking and increases the intracellular retention of Tf-TfR complexes in polarized Caco-2 cells. The alteration of TfR trafficking could conceivably have caused the increase of insulin transport across the intestinal barrier when Agg-Tf-S-S-In was administered orally to STZ-induced diabetic rats. The delayed onset and prolonged effect of Agg-Tf-S-S-In in hypoglycemia strongly suggests that the Tf-oligomer can act as a sustained release carrier in the oral delivery of protein and peptide drugs.     

Effect of linezolid on the 50% lethal dose and 50% protective dose in treatment of infections by gram-negative pathogens in naive and immunosuppressed mice and on the efficacy of ciprofloxacin in an acute murine model of septicemia

Murine models of infection were used to study the effect of linezolid on the virulence of Gram-negative bacteria and to assess potential pharmacodynamic interactions with ciprofloxacin in the treatment of these infections, prompted by observations from a recent clinical trial. Naive and immunosuppressed mice were challenged with Klebsiella pneumoniae 53A1109, K. pneumoniae GC6658, and Pseudomonas aeruginosa UC12120 in acute sepsis and pulmonary infection models, using different serial dilutions of these pathogens (groups of 8 animals each). Linezolid (100 mg/kg/dose) was administered orally at 0.5 and 4.0 h postchallenge in the sepsis model and at 4 h postchallenge followed by 2 days of twice-daily treatment in the pulmonary model. Further, ciprofloxacin alone and in combination with oral linezolid was investigated in the sepsis model. Survival was assessed for 4 and 10 days postchallenge in the systemic and respiratory models, respectively. The data were fitted to a nonlinear regression analysis to determine 50% lethal doses (LD(50)s) and 50% protective doses (PD(50)s). A clinically relevant, high-dose regimen of linezolid had no significant effect on LD(50) in these models. This lack of effect was independent of immune status. A combination of oral ciprofloxacin with linezolid yielded lower PD(50)s than oral ciprofloxacin alone (ciprofloxacin in combination, 8.4 to 32.7 mg/kg; oral ciprofloxacin, 39.4 to 88.3 mg/kg). Linezolid did not improve the efficacy of subcutaneous ciprofloxacin (ciprofloxacin in combination, 2.0 to 2.4 mg/kg; subcutaneous ciprofloxacin, 2.0 to 2.8 mg/kg). In conclusion, linezolid does not seem to potentiate infections caused by Gram-negative pathogens or to interact antagonistically with ciprofloxacin.     

Decreased oral absorption of cyclosporine A after liver ischemia-reperfusion injury in rats: the contribution of CYP3A and P-glycoprotein to the first-pass metabolism in intestinal epithelial cells

The bioavailability of orally administrated cyclosporine A (CsA) is poor and variable in liver transplantation recipients. Little information is available about the effect of liver ischemia-reperfusion (I/R) injury, which is associated with liver transplantation, on the intestinal first-pass metabolism of CsA. In the present study, we investigated the pharmacokinetics of CsA after liver I/R and assessed the effect of liver I/R via CYP3A and P-glycoprotein (P-gp) on its intestinal first-pass metabolism. When CsA alone was administrated orally, the area under the concentration-time curve (AUC) in the I/R rats was significantly decreased compared with that in the sham rats. On the other hand, there were no significant differences in the AUC between I/R and sham rats when CsA was administrated intravenously or orally with ketoconazole. After intraloop administration of CsA to the small intestine (upper, middle, and lower portions) of the I/R and sham rats, the AUC(0-15 min) in the upper intestine was significantly lower in the I/R rats than in the sham rats. CYP3A activity and the expression levels of P-gp in the upper intestine of the I/R rats were significantly higher than those of the sham rats. Our study clearly demonstrates for the first time that liver I/R decreases the oral bioavailability of CsA and that this is attributable principally to increased first-pass metabolism mediated by CYP3A and P-gp in the upper small intestine. The present findings provide useful information for the etiology of liver I/R injury and appropriate use of CsA after liver transplantation.     

In vivo activities of peptidic prodrugs of novel aminomethyl tetrahydrofuranyl-1 beta-methylcarbapenems

A series of novel aminomethyl tetrahydrofuranyl (THF)-1 beta-methylcarbapenems which have excellent broad-spectrum antibacterial activities exhibit modest efficacies against acute lethal infections (3.8 mg/kg of body weight against Escherichia coli and 0.9 mg/kg against Staphylococcus aureus) in mice when they are administered orally. In an effort to improve the efficacies of orally administered drugs through enhanced absorption by making use of a peptide-mediated transport system, several different amino acids were added at the aminomethyl THF side chains of the carbapenem molecules. The resulting peptidic prodrugs with L-amino acids demonstrated improved efficacy after oral administration, while the D forms were less active than the parent molecules. After oral administration increased (3 to 10 times) efficacy was exhibited with the alanine-, valine-, isoleucine-, and phenylalanine-substituted prodrugs against acute lethal infections in mice. Median effective doses (ED50s) of < 1 mg/kg against infections caused by S. aureus, E. coli, Enterobacter cloacae, or penicillin-susceptible Streptococcus pneumoniae were obtained after the administration of single oral doses. Several of the peptidic prodrugs were efficacious against Morganella morganii, Serratia marcescens, penicillin-resistant S. pneumoniae, extended-spectrum beta-lactamase-producing Klebsiella pneumoniae, and E. coli infections, with ED50s of 1 to 14 mg/kg by oral administration compared with ED50s of 14 to > 32 mg/kg for the parent molecules. In general, the parent molecules demonstrated greater efficacy than the prodrugs against these same infections when the drugs were administered by the subcutaneous route. The parent molecule was detectable in the sera of mice after oral administration of the peptidic prodrugs.     

Epithelial heparin delivery via microspheres mitigates experimental colitis in mice

Low-molecular-weight heparins (LMWH) have been shown to be efficient in the treatment of inflammatory bowel disease (IBD). Parenteral heparin therapy, however, may cause hemorrhagic adverse effects. To reduce this risk, epithelial LMWH delivery in combination with a system ensuring selective drug release to the inflamed tissue was tested here. Enoxaparin loaded microspheres (MS) were administered orally to male BALB mice suffering from a pre-existing experimental colitis, whereas control groups received subcutaneous or rectal LMWH solution. Colon weight/length index and alkaline phosphatase and myeloperoxidase activities were assessed to determine the inflammation. Tissue penetration experiments elucidated the processes involved in the proposed new therapeutic approach. Oral LMWH-MS proved to be equally efficient in mitigating experimental colitis as rectally administered LMWH solution when quantified by myeloperoxidase activity (MS, 10.2+/-1.5 U/mg tissue; rectal, 9.2+/-1.6 U/mg) and to be superior to subcutaneous LMWH (s.c., 21.6+/-5.6 U/mg; untreated colitis control, 30.0+/-3.8 U/mg). Pharmacokinetic studies found a notably low systemic availability of oral LMWH delivered from MS (<5%) indicating a low potential for adverse effects. The tissue permeability was selectively enhanced in the inflamed regions where a 9-fold higher LMWH penetration was found compared with healthy tissue. Epithelial LMWH delivery has been found a promising anti-inflammatory therapeutic approach. The use of LMWH-MS in this context offers a promising tool for IBD therapy by enhancing specifically drug availability at inflamed tissue sites while reducing the risk for systemic adverse effects to a negligibly low level.     

Voriconazole concentration in human aqueous humor and plasma during topical or combined topical and systemic administration for fungal keratitis

Voriconazole (VRC) is an antifungal drug that effectively treats keratitis caused by yeasts and molds when administered orally. We retrospectively evaluated clinical outcomes and plasma and aqueous humor drug concentrations in five patients with fungal keratitis and one patient with posttraumatic endophthalmitis who were treated with VRC. VRC was administered either topically (1% eye drops every hour) or orally (400 mg twice a day). Plasma and aqueous humor samples from affected eyes were taken 12 h after oral administration or 1 h after eye drop application. The drug concentration was measured by liquid chromatography with UV or mass spectrometric detection. All six patients responded well to VRC treatment. The VRC concentration ranged from 2.93 to 3.40 mg/liter in the aqueous humor and from 3.20 to 4.20 mg/liter in the plasma after combined oral and topical treatment. Topical administration alone resulted in highly variable trough VRC concentrations of 0.61 to 3.30 mg/liter in the aqueous humor. VRC concentrations were above the MIC for Candida albicans Aspergillus fumigatus and clinical improvement was seen in all four patients with C. albicans and A. fumigatus keratitis. Combined orally and topically administered VRC resulted in aqueous humor drug concentrations of > or =2.93 mg/liter, which is above the VRC MIC for most fungi. Topical VRC treatment resulted in an aqueous humor drug concentration >0.61 mg/liter, which is above the MIC for most Candida species. The results from this small series of patients suggest that both topical and combined systemic and topical VRC therapy can be effective in treating fungal keratitis. Furthermore, the data provide preliminary support for initiation of VRC treatment with a combined topical and systemic administration until the causative fungus and its MIC are identified.     

Oral heparins

The antithrombotic drug heparin is administered parenterally and believed not effective orally. Oral heparin would be most suitable for long term administration, often required for the prevention of thrombosis. Following parenteral administration, heparin is taken up by endothelial cells. Our laboratory has shown that heparin is similarly taken up by endothelium following oral administration, despite low plasma heparin concentrations. In a twenty-four hour period, endothelial heparin concentrations are greatest within 15 minutes of oral dosing although plasma levels never exceed one percent of dose. Endothelial uptake accounts for a considerable amount of absorption if the total body endothelium is considered. In support of oral heparin absorption, we demonstrated a dose-dependent decrease in thrombosis incidence in a rat jugular vein model following single oral doses of unfractionated heparins (bovine and porcine) or low molecular weight heparins (reviparin, logiparin and ardeparin). Low molecular weight heparins were effective at lower doses than unfractionated heparins where a fifty percent reduction in thrombosis was observed with 0.025 mg/kg reviparin, 0.1 mg/kg logiparin, versus 7.5 mg/kg bovine unfractionated heparin. These studies support the work of others demonstrating measurable systemic changes following oral heparin administration and suggest that heparin may be effective when administered by the oral route. It also indicates that the presence of heparin in plasma likely reflects a much greater amount associated with endothelium.     

Enhanced anti-inflammatory potency of a nitric oxide-releasing derivative of flunisolide: role of nuclear factor-kappaB

Glucocorticoids remain among the most commonly used anti-inflammatory drugs, despite significant adverse effects. Other anti-inflammatory drugs, including aspirin, have been coupled through an ester linkage to a nitric oxide-releasing moiety, resulting in an increase in potency and a decrease in adverse effects. Prednisolone has similarly been modified, with marked improvement of its therapeutic index. In the present study, we have evaluated whether a nitric oxide-releasing derivative of another glucocorticoid, flunisolide, would increase its potency as an anti-inflammatory agent and would decrease its systemic toxicity. To evaluate anti-inflammatory potency and efficacy, the carrageenan-airpouch model in the rat was used. Flunisolide and NCX-1024 (flunisolide-21-[4'-(nitrooxymethyl) benzoate]) were compared across a range of doses, with both direct injection into the airpouch and oral administration. The ability of these agents to protect the stomach against indomethacin-induced damage also was assessed. Effects of oral administration of the two drugs on body weight gain and adrenal suppression were also evaluated. With direct application into the airpouch, NCX-1024 was found to be 41 times more potent than flunisolide in reducing leukocyte accumulation and prostaglandin E2 generation. The increased potency may be related to an enhanced ability of NCX-1024 to prevent nuclear factor-kappaB activation. When given orally, the two compounds exhibited similar potency. However, orally administered NCX-1024 was more potent at protecting against indomethacin-induced gastric damage, caused less reduction of body weight, and, unlike flunisolide, did not cause adrenal atrophy. These studies suggest that NCX-1024 may be an attractive alternative to conventional glucocorticoids, particularly for applications involving topical administration.     

Biodegradable nanoparticles for targeted drug delivery in treatment of inflammatory bowel disease

The use of nanoparticles for targeted oral drug delivery to the inflamed gut tissue in inflammatory bowel disease was examined. Such a strategy of local drug delivery would be a distinct improvement compared with existing colon delivery devices for this disease. An experimental colitis was induced by trinitrobenzenesulfonic acid to male Wistar rats. Rolipram, an anti-inflammatory model drug, was incorporated within poly(lactic-coglycolic acid) nanoparticles, which were administered once a day orally for five consecutive days. A clinical activity score and myeloperoxidase activity were determined to assess the inflammation, whereas an adverse effect index reflected the remaining neurotropic effect of rolipram resulting from its systemic absorption. All nanoparticle formulations proved to be as efficient as the drug in solution in mitigating the experimental colitis. The clinical activity score and myeloperoxidase activity decreased significantly after the oral administration of rolipram nanoparticles or solution. During the next 5 days when animals were kept without drug treatment the drug solution group displayed a strong relapse, whereas the nanoparticle groups continued to show reduced inflammation levels. The rolipram solution group had a high adverse effect index, whereas the rolipram nanoparticle groups proved their potential to retain the drug from systemic absorption as evidenced by a significantly reduced index. This new delivery system enabled the drug to accumulate in the inflamed tissue with higher efficiency than when given as solution. The nanoparticle deposition in the inflamed tissue should be given particular consideration in the design of new carrier systems for the treatment of inflammatory bowel disease.     

Marked suppression of secondary hyperparathyroidism by intravenous administration of 1,25-dihydroxy-cholecalciferol in uremic patients

Current evidence suggests that administration of 1,25(OH)2D3 to patients with chronic renal insufficiency results in suppression of secondary hyperparathyroidism only if hypercalcemia occurs. However, since the parathyroid glands possess specific receptors for 1,25(OH)2D3 and a calcium binding protein, there is considerable interest in a possible direct effect of 1,25(OH)2D3 on parathyroid hormone (PTH) secretion independent of changes in serum calcium. Recent findings indicate substantial degradation of 1,25(OH)2D3 in the intestine, therefore, it is possible that while oral administration of the vitamin D metabolite increases intestinal calcium absorption, the delivery of 1,25(OH)2D3 to peripheral target organs may be limited. We therefore compared the effects of orally or intravenously administered 1,25(OH)2D3 on the plasma levels of 1,25(OH)2D3 and the effects of these two modes of treatment on PTH secretion. Whereas oral administration of 1,25(OH)2D3 in doses adequate to maintain serum calcium at the upper limits of normal did not alter PTH levels, a marked suppression (70.1 +/- 3.2%) of PTH levels was seen in all 20 patients given intravenous 1,25(OH)2D3. Temporal studies suggested a 20.1 +/- 5.2% decrease in PTH without a significant change in serum calcium with intravenous 1,25(OH)2D3. In five patients the serum calcium was increased by the oral administration of calcium carbonate, the decrement in serum i-PTH was only 25 +/- 6.65% when compared with 73.5 +/- 5.08% (P less than 0.001) obtained by the administration of intravenous 1,25(OH)2D3. Thus, a similar serum calcium achieved by intravenous 1,25(OH)2D3 rather than calcium carbonate has a greater suppressive effect in the release of PTH. These studies indicate that 1,25(OH)2D3 administered intravenously rather than orally may result in a greater delivery of the vitamin D metabolite to peripheral target tissues other than the intestine and allow a greater expression of biological effects of 1,25(OH)2D3 in peripheral tissues. The use of intravenous 1,25(OH)2D3 thus provides a simple and extremely effective way to suppress secondary hyperparathyroidism in dialysis patients.     

Efficacy of orally delivered cochleates containing amphotericin B in a murine model of aspergillosis

Cochleates containing amphotericin B (CAMB) were administered orally at doses ranging from 0 to 40 mg/kg of body weight/day for 14 days in a murine model of systemic aspergillosis. The administration of oral doses of CAMB (20 and 40 mg/kg/day) resulted in a survival rate of 70% and a reduction in colony counts of more than 2 logs in lungs, livers, and kidneys. Orally administered CAMB shows promise for the treatment of aspergillosis.     

Oral antibiotic therapy of serious systemic infections

Traditionally, antibiotics have been administered intravenously (IV) for serious systemic infections. As more potent oral antibiotics were introduced, and their pharmacokinetic aspects studied, orally administered antibiotics have been increasingly used for serious systemic infections. Antibiotics ideal for oral administration are those that have the appropriate spectrum, high degree of activity against the presumed or known pathogen, and have good bioavailability. Oral antibiotics with high bioavailability, that is > or = 90% absorbed, achieve serum/tissue concentrations comparable to IV administered antibiotics at the same dose. The popularity of "IV to PO switch therapy" is possible because of the availability of many potent oral antibiotics with high bioavailability. Initial IV therapy is appropriate in patients who are in shock/have impaired intestinal absorption, but after clinical defervescence, completion of therapy should be accomplished with oral antibiotics. As experience with "IV to PO switch therapy" has accumulated, confidence in oral antimicrobics for therapy of serious systemic infections has continued to increase. The trend in treating serious systemic infections entirely with oral antimicrobial therapy will continue, and is clearly the wave of the future.     

In vivo evaluation of tigemonam, a novel oral monobactam.

Tigemonam, a new monobactam with excellent activity against gram-negative bacteria, was evaluated for in vivo efficacy and absorption after oral administration to laboratory animals. Tigemonam is absorbed when administered orally to mice and dogs. In a variety of gram-negative systemic infections in mice, orally administered tigemonam was efficacious in all infections studied. Comparison drugs such as amoxicillin, cephalexin, and cefaclor were less efficacious, especially in infections caused by beta-lactamase-producing organisms. In localized infections, tigemonam also demonstrated excellent in vivo activity. In acute pyelonephritis in mice caused by Escherichia coli or Proteus sp., tigemonam was very effective. In a rat lung model with Klebsiella pneumoniae, tigemonam was active with a median effective dose of 46 mg/kg compared with 160 mg/kg for cefaclor and over 200 mg/kg for amoxicillin. Tigemonam was well absorbed in laboratory animals and with its excellent gram-negative spectrum of activity should prove of value in oral antibiotic therapy in humans.     

Hochuekkito, a Kampo (traditional Japanese herbal) Medicine, Enhances Mucosal IgA Antibody Response in Mice Immunized with Antigen-entrapped Biodegradable Microparticles

The effect of oral administration of Hochuekkito (HET; Bu-Zhong-Yi-Qi-Tang in Chinese), a traditional Japanese herbal medicine, on mucosal IgA immune response was investigated. To induce the antigen-specific antibodies in mucosal site, ovalbumin (OVA)-entrapped biodegradable microparticles (OVA-microparticles) were used as an antigen. Mice were orally immunized with OVA-microparticles for 3 successive days with intragastric gavage. From 7 days after the onset of immunization, the mice were boosted twice a week with the same antigen for 2 weeks. HET or water alone was orally administered to the mice via the intragastric route from 7 days before to 27 days after the onset of immunization. Although no significant change in total secretory IgA antibody level was observed in intestinal and nasal washes, OVA-specific IgA titers in intestinal washes were significantly enhanced by oral administration of HET. When lymphocytes from spleen, peripheral blood and Payer's patches were investigated for cytokines production, it was found that the IFN-γ secretion from the lymphocytes was increased by the administration of HET. Microarray analysis of Peyer's patch cells revealed enhanced expression of L-selectin gene. The increase of L-selectin positive cells in B lymphocytes fraction was observed in Peyer's patch cells and peripheral blood mononuclear cells by flow cytometry. These results suggest that the enhanced IFN-γ secretion and increased population of L-selectin positive B lymphocytes by orally administered HET may partly contribute to enhancement of IgA immune response against intestinal antigens, and orally administered HET may strengthen defensive systems against various pathogens and food antigens in intestine.     

Systemic peptide delivery via the stomach: in vivo evaluation of an oral dosage form for salmon calcitonin.

It was the aim of this study to investigate the potential of stomach targeted delivery systems for systemic peptide administration using salmon calcitonin as a model drug. Chitosan was modified by the immobilization of thiol groups utilizing 2-iminothiolane in order to obtain a chitosan-4-thiobutylamidine conjugate (chitosan-TBA). Furthermore, a chitosan-pepstatin A conjugate was synthesized by a carbodiimide mediated linkage of the pepsin inhibitor to the polymer. The protective effect of this novel conjugate for calcitonin towards pepsin was evaluated in vitro. Minitablets (5 mg) were generated by direct compression of calcitonin, chitosan, chitosan-TBA, chitosan-pepstatin A conjugate and glutathione (GSH), respectively (A, 1:0:69:20:10; B, 1:79:0:20:0; C, 1:99:0:0:0). The drug release was investigated in an artificial gastric fluid. Biofeedback studies were performed in rats by determining the decrease in plasma calcium level after oral administration. The novel chitosan-pepstatin A conjugate displayed 291+/-58 nmol inhibitor per gram polymer (mean+/-S.D., n = 5). The chitosan-inhibitor conjugate showed a very strong protective effect for salmon calcitonin towards pepsinic degradation. A controlled drug release was provided by all tested dosage forms-A, B and C. Dosage form B led only to a slight reduction of the plasma calcium level, displaying a pharmacological efficacy versus i.v. injection of 0.41%, while dosage form C did not lead to any significant effect. In contrast, dosage form A led to a decrease in the plasma calcium level of 10% for at least 12 h. The pharmacological efficacy of this formulation was determined to be 1.35%. The study suggests that stomach targeted oral delivery might be a promising novel approach for noninvasive systemic peptide administration.     

Tricaprylin microemulsion for oral delivery of low molecular weight heparin conjugates.

Heparin is available to patients only by parenteral administrations due to its low oral bioavailability. For the oral delivery of low molecular weight heparin (LMWH), LMWH-DOCA was synthesized by chemical conjugation of LMWH and deoxycholic acid (DOCA) and this conjugate was formulated in a microemulsion system. The coupling ratios of DOCA to LMWH for LD1 and LD2 were 1.33 and 2.37, respectively. The microemulsion was composed of tricaprylin, surfactant mixture (Tween 80 and Span 20) and LMWH-DOCA in water, and their volume ratio was 5:3:1:1. Pharmacokinetic parameters of LMWH were not significantly changed by conjugation with DOCA; however, when LMWH-DOCA in tricaprylin microemulsion was orally administered in mice, its bioavailability was increased up to 1.5%. Furthermore, the enhancing effect of the conjugated DOCA in the tricaprylin microemulsion on the absorption of LMWH in the intestine was more significantly increased in monkey than in mice. Since the tricaprylin microemulsion could dissolve LMWH-DOCA, this formulation could maximize the enhancing effect of the conjugated DOCA on the absorption of LMWH in the intestine. Finally, it was expected that 20 mg/kg of LMWH-DOCA in the tricaprylin microemulsion was enough to prevent deep vein thrombosis (DVT) and pulmonary embolism (PE).     

Oral uptake and translocation of a polylysine dendrimer with a lipid surface.

A series of lipidic peptide dendrimers based on lysine with 16 surface alkyl (C(12)) chains has been synthesised in our laboratories. One of the series, a fourth generation dendrimer with a diameter of 2.5 nm was chosen to study its absorption after oral administration to female Sprague-Dawley rats (180 g, 9 weeks old). It was synthesised as the tritiated derivative (all acetyl portions) and had a molecular weight of 6300 and log P (octanol/water) of 1.24. First a single oral dose 14 mg/kg was administered by gavage. Maximum levels of dendrimer observed were 15% in the small intestine, 5% in the large intestine and 3% in the blood at 6 h after administration, while 1.5% reached the liver, 0.1% the spleen and 0. 5% the kidneys. In a parallel study with a higher dose of 28 mg/kg, approximately 1% was absorbed via Peyer's patches of the small intestine at 3 h. The maximum uptake by small intestine enterocytes was 4% of the dose after 3 h. After 12 h, 0.3 and 4% dendrimer was measured respectively in Peyer's patches and enterocytes of the large intestine. When calculated on the basis of target tissue weight, the total percentage of the dose absorbed through Peyer's patches was greater than through normal enterocytes in the small intestine after 3 and 24 h, but the opposite was true in the large intestine. These levels of uptake and translocation are lower than those exhibited by polystyrene particles in the range from 50 to 3000 nm. This might suggest that there is an optimum size for nanoparticulate uptake by the gut.