Biomedical subjects

J C Verhoef

Publications and source records attributed to J C Verhoef.

At least 37 records · Page 2Linked to original sources

PubMed2000

Effect of degree of quaternization of N-trimethyl chitosan chloride for enhanced transport of hydrophilic compounds across intestinal caco-2 cell monolayers.

N-Trimethyl chitosan chloride (TMC) is a permanently quaternized chitosan derivative with improved aqueous solubility compared to native chitosan. TMC is able to open the tight junctions of intestinal epithelia at physiological pH values, where chitosan is insoluble and therefore ineffective. TMCs with degrees of substitution of 40 and 60% were synthesized according to a novel synthesis procedure and their effect on the permeability of the tight junctions of the intestinal Caco-2 monolayers was studied, measuring the transepithelial electrical resistance and the transport of a mainly paracellularly transported compound, [14C]-mannitol. Toxicity studies using nucleic stains were done to establish the transport as a cause of opening of the tight junctions and not of possible cytotoxicity. TMC60 showed higher transport enhancement ratios than TMC40 in all concentrations tested (0.05-1. 0%, w/v). Both derivatives did not affect the viability of the Caco-2 cell monolayers. These results suggest that high charge density is necessary for TMC to substantially improve the paracellular permeability of intestinal epithelia. It is expected that TMC40 and TMC60 will enhance the intestinal permeation of hydrophilic macromolecular drugs such as peptides and proteins.

Biocompatible Materials↗

PubMed2000

Intestinal absorption of octreotide: N-trimethyl chitosan chloride (TMC) ameliorates the permeability and absorption properties of the somatostatin analogue in vitro and in vivo.

Octreotide acetate is a somatostatin analogue used for the control of endocrine tumors of the gastrointestinal (GI) tract and the treatment of acromegaly. The oral absorption of octreotide is limited because of the limited permeation across the intestinal epithelium. Both chitosan hydrochloride and N-trimethyl chitosan chloride (TMC), a quaternized chitosan derivative, are nonabsorbable and nontoxic polymers that have been proven to effectively increase the permeation of hydrophilic macromolecules across mucosal epithelia by opening the tight junctions. This study investigates the intestinal absorption of octreotide when it is coadministered with the polycationic absorption enhancer TMC. Caco-2 cell monolayers were used as an in vitro intestinal epithelium model, and male Wistar rats were used for in vivo studies. Octreotide with or without polymers (TMC; chitosan hydrochloride) was administered intrajejunally in rats, and serum peptide levels were measured by radioimmunoassay. All applications and administrations were performed at neutral pH values (i.e., pH = 7.4). In vitro transport studies with Caco-2 cells revealed an increased permeation of octreotide in the presence of TMC. Enhancement ratios ranged from 34 to 121 with increasing concentrations of the polymer (0.25-1.5%, w/v). In rats, 1.0% (w/v) TMC solution significantly increased the absorption of the peptide analogue, resulting in a 5-fold increase of octreotide bioavailability compared with the controls (octreotide alone). Coadministration of 1.0% (w/v) chitosan hydrochloride did not enhance octreotide bioavailability. These results in combination with the nontoxic character of TMC suggest that this polymer is a promising excipient in the development of solid dosage forms for the peroral delivery and intestinal absorption of octreotide.

Algorithms↗

PubMed2000

N-trimethylated chitosan chloride (TMC) improves the intestinal permeation of the peptide drug buserelin in vitro (Caco-2 cells) and in vivo (rats).

PURPOSE: To evaluate N-trimethyl chitosan chloride (TMC) of high degrees of substitution as intestinal permeation enhancers for the peptide drug buserelin in vitro using Caco-2 cell monolayers, and to investigate TMCs as enhancers of the intestinal absorption of buserelin in vivo, in rats. METHODS: TMCs were tested on Caco-2 cells for their efficiency to increase the paracellular permeability of the peptide buserelin. For the in vivo studies male Wistar rats were used and buserelin was administered with or without the polymers intraduodenally. Both types of experiments were performed at pH 7.2. RESULTS: Transport studies with Caco-2 cell monolayers confirmed that the increase in buserelin permeation is dependent on the degree of trimethylation of TMC. In agreement with the in vitro results, in vivo data revealed highly increased bioavailability of buserelin following intraduodenal co-administration with 1.0% (w/v) TMCs. Intraduodenally applied buserelin resulted in 0.8% absolute bioavailability, whereas co-administrations with TMCs resulted in mean bioavailability values between 6 and 13 %. Chitosan HCl (1.0%; pH = 7.2) did not significantly increase the intestinal absorption of buserelin. CONCLUSIONS: Both the in vitro and in vivo results indicate that TMCs are potent mucosal permeation enhancers of the peptide drug buserelin at neutral pH values.

Animals↗

PubMed1999

Recent advances in buccal drug delivery and absorption--in vitro and in vivo studies.

In the first part of this study, the aim was to characterize transport of fluorescein isothiocyanate (FITC)-labelled dextrans of different molecular weights as model compounds for peptides and proteins through buccal mucosa. The penetration of these dextrans through porcine buccal mucosa (a nonkeratinized epithelium, comparable to human buccal mucosa) was investigated by measuring transbuccal fluxes and by analyzing the distribution of the fluorescent probe in the epithelium, using confocal laser scanning microscopy for visualizing permeation pathways. The results revealed that passage of hydrophilic compounds such as the FITC-dextrans through porcine buccal epithelium is restricted to permeants with a molecular weight lower than 20 kDa. The permeabilities of buccal mucosa for the 4 and 10 kDa FITC-dextran (of the order of 10(-8) cm/s) were not significantly different from each other or from the much smaller compound FITC. The confocal images of the distribution pattern of FITC-dextrans showed that the paracellular route is the major pathway through buccal epithelium. In the in vivo part of this study, buccal delivery of FITC-labelled dextran 4400 (FD4) and the peptide drug buserelin was investigated in vivo, in pigs. The delivery device consisted of an application chamber with a solution of FD4 or buserelin, and was attached to the buccal mucosa for 4 h using an adhesive patch. A randomized cross-over study including intravenous administration and buccal delivery without and with 10 mM sodium glycodeoxycholate (GDC) as an absorption enhancer was performed in pigs. After buccal administration, steady-state plasma levels were rapidly achieved. Co-administration of 10 mM GDC increased the absolute bioavailability from 1.8+/-0.5 to 12.7+/-2.0% for FD4. From the present studies, it is concluded that buccal administration is a suitable route for the delivery for macromolecules and hydrophilic compounds such as peptide drugs.

Animals↗

PubMed1999

TR146 cells grown on filters as a model of human buccal epithelium: permeability of fluorescein isothiocyanate-labelled dextrans in the presence of sodium glycocholate.

The aim of the present study was to characterize the TR146 cell culture model as an in vitro model of human buccal epithelium with respect to the permeability of test substances with different molecular weights (M(w)). For this purpose, the apparent permeability (P(app)) values for mannitol and for fluorescein isothiocyanate (FITC)-labelled dextrans (FD) with various M(w) (4000-40000) were compared to the P(app) values obtained using porcine buccal mucosa as an in vitro model of the human buccal epithelium. The effect of 10 mM sodium glycocholate (GC) on the P(app) values was examined. To identify the pathways by which FD of M(w) 4000-40000 were transported, the confocal laser scanning microscope (CLSM) was used. The P(app) values obtained with the TR146 cell culture model in the absence of a permeability enhancer linearly decreased with increasing M(w) of the test substance from 0. 65+/-0.055x10(-8) to 44+/-7.5x10(-8) cm/s, as the P(app) values obtained with porcine buccal mucosa. In the presence of the permeability enhancer, GC, the permeability of the FD across the cultured TR146 cell culture model increased in a parabolic manner, reaching maximum at M(w) 10000. In the absence of the enhancer, only paracellular localization of FD was observed while, in the presence of GC, FD also could be detected in the cytosol of some of the superficial cells. The GC-induced enhancement of FD permeation may be partially attributed to changed permeation pathways. The present results indicate that the TR146 cell culture model is a suitable in vitro model for mechanistic permeability studies of human buccal drug permeability.

Animals↗

PubMed1999

Effects of N-trimethyl chitosan chloride, a novel absorption enhancer, on caco-2 intestinal epithelia and the ciliary beat frequency of chicken embryo trachea.

N-trimethyl chitosan (TMC) polymers are quaternized chitosans in different degrees of trimethylation. These polymers enhance the absorption of macromolecules through mucosal epithelia by triggering the reversible opening of tight junctions and only allow for paracellular transport. To investigate the safety of these novel absorption enhancers cytotoxicity and ciliotoxicity studies have been performed. Intestinal Caco-2 cell monolayers were chosen to study possible membrane damaging effects of these polymers, using confocal laser scanning microscopy visualization of nuclear staining by a membrane impermeable fluorescent probe during transport of the paracellular marker Texas red dextran (MW 10 000). Ciliated chicken embryo trachea tissue was used to study the effect of the polymers on the ciliary beat frequency (CBF) in vitro. In both studies the TMC polymers of different degrees of substitution (20, 40 and 60%) were tested at a concentration of 1.0% (w/v). No substantial cell membrane damage could be detected on the Caco-2 cells treated with TMCs, while the effect on the CBF in vitro was found to be marginal. TMC60 and TMC40 enhance paracellular transport of Texas red dextran in Caco-2 cell monolayers, whereas TMC20 is ineffective. In conclusion, TMCs of high degrees of substitution may be effective and safe absorption enhancers for peptide and protein drug delivery.

Animals↗

PubMed1999

The effect of methylated beta-cyclodextrins on the tight junctions of the rat nasal respiratory epithelium: electron microscopic and confocal laser scanning microscopic visualization studies.

The nasal absorption enhancer randomly methylated beta-cyclodextrin (RAMEB) is thought to increase the paracellular permeability of the nasal epithelium by opening of the tight junctions. The effects of RAMEB on the cytoskeleton of the rat nasal epithelium in vivo were determined by confocal laser scanning microscopy (CLSM). The effects on the tight junctions of the rat nasal epithelium were also investigated, using transmission electron microscopy (TEM) of thin sections. The effects of RAMEB were compared with those of the absorption enhancer sodium taurodihydrofusidate (STDHF). Fifteen minutes after nasal administration of 2% RAMEB in vivo, the distribution of cytoskeletal actin was comparable to the untreated control, suggesting that RAMEB does not cause opening of the tight junctions via cytoskeletal interactions. In contrast, administration of 1% STDHF resulted in changes in the actin staining. Furthermore, with TEM severe damage of the nasal epithelium was observed after treatment with 1% STDHF. Ultrastructural changes of the tight junctions were not apparent in TEM sections after treatment with 2% RAMEB. In conclusion, CLSM and TEM are suitable methods to visualize the effects of absorption enhancers on nasal epithelial morphology.

Actins↗

PubMed1999

Chitosan for enhanced intestinal permeability: prospects for derivatives soluble in neutral and basic environments.

In this study the effects of two chitosan salts, namely chitosan hydrochloride and chitosan glutamate (0.5 and 1.5% w/v), on the transepithelial electrical resistance (TEER) and permeability of Caco-2 cell monolayers, using the radioactive marker [14C]-mannitol, were investigated in a slightly acidic (pH 6.2) and neutral (pH 7.4) environment. Both salts are soluble in acidic conditions up to a concentration of 1.5% w/v and solutions of this strength, at a pH of 6.2, caused a pronounced lowering in the TEER of Caco-2 cell monolayers in the order of 70+/-1% (chitosan glutamate) and 77+/-3% (chitosan hydrochloride), 20 min after incubation started. In agreement with the TEER results the transport of the radioactive marker, [14C]-mannitol, was increased 25-fold (chitosan glutamate) and 36-fold (chitosan hydrochloride), respectively, at this pH. However, at a pH of 7.4 both salts are insoluble and prove to be ineffective since no reduction in the TEER values or increase in the transport of [14C]-mannitol were found. The results show that these chitosan salts are potent absorption enhancers in acidic environments. We conclude that there is a need for chitosan derivatives with increased solubility, especially at neutral and basic pH values, for use as absorption enhancers aimed at the delivery of therapeutic compounds in the more basic environment of the large intestine and colon.

Caco-2 Cells↗

PubMed1999

Effect of the degree of quaternization of N-trimethyl chitosan chloride on the permeability of intestinal epithelial cells (Caco-2).

N-trimethyl chitosan chloride (TMC), a partially quaternized derivative of chitosan with superior water solubility, was synthesized with different degrees of quaternization [12.6% quaternized (TMC-L) and 19.9% quaternized (TMC-H)] and the effects of these novel polymers on the permeability of intestinal epithelial cells were investigated in Caco-2 cell monolayers. Transepithelial electrical resistance (TEER) measurements showed that both polymers in 1.5-2.5% w/v concentrations caused a pronounced, concentration dependent lowering in TEER values, but that TMC-H was more effective than TMC-L at similar concentrations (36 +/- 3% reduction with TMC-L and 53 +/- 6% reduction with TMC-H at 2.0% concentrations). Similar results were obtained in transport studies with the hydrophilic radioactive markers [14C]mannitol (MW 182.2) and [14C]polyethylene glycol 4000 ([14C]PEG 4000, MW 4000). The transport of [14C]mannitol was increased 51-fold (TMC-L) and 97-fold (TMC-H) at 2.5% concentrations. No deleterious effects to the cells could be demonstrated with trypan blue exclusion studies. The results show that TMC is able to open the tight junctions of intestinal epithelial cells to allow for paracellular transport of hydrophilic molecules. It is concluded that the charge density of TMC, as determined by the degree of quaternization, is an important factor determining its potential use as an absorption enhancer across intestinal epithelia.

Biological Transport↗

PubMed1999

Enhancement of paracellular drug transport with highly quaternized N-trimethyl chitosan chloride in neutral environments: in vitro evaluation in intestinal epithelial cells (Caco-2).

Previous studies have established that a partially quaternized derivative of chitosan, N-trimethyl chitosan chloride (TMC), can be used as an absorption enhancer for large hydrophilic compounds across mucosal surfaces. This study evaluates and compares the effects of the degree of quaternization of TMC, in a neutral environment, on the permeability of intestinal epithelial cells in vitro, where normal chitosan salts are ineffective as absorption enhancers. The effects of TMC-H [61.2% quaternized, (0.05-1.5% w/v)], TMC-L [12.3% quaternized, (0.5-1.5% w/v)], and chitosan hydrochloride [0.5-1.5% w/v] on the transepithelial electrical resistance (TEER) and permeability, for the hydrophilic model compound [14C]mannitol, of intestinal epithelial Caco-2 cell monolayers, were investigated at pH values of 6.20 and 7.40. The viability of the monolayers was checked with the trypan blue exclusion technique. At a pH of 6.20, all the polymers caused a pronounced reduction (37-67% at 0.5% w/v concentrations) in the TEER of Caco-2 cells. On the contrary, at a pH of 7.40, only TMC-H was able to decrease the TEER values, even in a concentration as low as 0.05% w/v (35% reduction). Comparable results were obtained with the permeation of [14C]mannitol. Large increases in the transport rate (18-23-fold at 0.5% w/v concentrations) were found at pH 6.20, whereas only TMC-H was able to increase the permeation of [14C]mannitol at pH 7.40 (31-48-fold at 0.05-1.5% w/v concentrations of TMC-H). For all the polymers studied, no deleterious effects to the cells could be demonstrated with the trypan blue exclusion technique. It is concluded that highly quaternized TMC is a potent absorption enhancer and the potential use of this polymer, especially in neutral and basic environments where normal chitosan salts are not effective, is expected to be an important contribution to the development of effective delivery systems for hydrophilic compounds such as peptide drugs.

Biological Transport↗

PubMed1999

Validation of animal experiments on ciliary function in vitro. I. The influence of substances used clinically.

In vitro studies of ciliary activity require specimens of healthy epithelium in relatively large quantities. Since human material is difficult to obtain, fresh chicken trachea samples have frequently been used in function experiments. The aim of the present study was to investigate whether several substances had comparable effects on the ciliary beat frequency (CBF) of chicken trachea and cryopreserved human respiratory epithelium obtained from the sphenoidal sinus. For this study, we used two topical anaesthetics: cocaine (3% and 7%) and lidocaine (2%). These anaesthetic substances were adjusted to pH 6 and pH 7. We also used two decongestants, namely xylometazoline 0.1% and oxymetazoline 0.1%, and the beta-blocking agent propranolol. Topical anaesthetics appeared to be more ciliostatic in solutions with pH 7 compared to pH 6. Complete ciliostatic effects were reversible, with the exception of the ciliostasis induced by propranolol. The effects of these substances on the CBF of fresh chicken trachea and cryopreserved human tissue did not differ significantly. These experiments show that chicken trachea constitutes a valid substitute for human material in studying ciliary activity in vitro. Moreover, the experiments provide evidence in support of the assumption that cryopreservation has no effect on ciliary reactivity as expressed by the CBF.

Adrenergic beta-Antagonists↗

PubMed1999

Validation of animal experiments on ciliary function in vitro. II. The influence of absorption enhancers, preservatives and physiologic saline.

Ciliary beat frequency (CBF) is one of the most important parameters of mucociliary clearance. Previously, we demonstrated that mucosa from chicken embryo trachea is a good substitute for human ciliated epithelium to study the effects on CBF of substances that are used clinically. In this study, we examined the effect on CBF of four excipients for nasal drug formulations: the absorption enhancers methylated beta-cyclodextrin 2% and sodium taurodihydrofusidate 1%, the preservative benzalkonium chloride 0.01%, and physiologic saline. We also examined the effect on CBF of the cryopreservative dimethyl sulfoxide, which is used to protect ciliated epithelium prior to storage in liquid nitrogen. Results obtained with chicken embryo trachea were compared with those of cryopreserved human mucosa taken from the sphenoidal sinus. For all of the substances tested, the effects on CBF of chicken material were comparable to those measured on human material. Benzalkonium chloride had a stronger ciliostatic effect on human tissue. After 60 min, however, the effect of that substance on CBF was similar in both tissues. We conclude that chicken embryo trachea can be used as a substitute for human ciliated mucosa when studying ciliary activity in vitro.

Animals↗

PubMed1998

Comparison of the effect of different chitosan salts and N-trimethyl chitosan chloride on the permeability of intestinal epithelial cells (Caco-2).

A partially quaternized chitosan derivative, N-trimethyl chitosan chloride (TMC) (degree of quaternization 12.28%), was synthesized and the effects of this novel polymer on the permeability of intestinal epithelial cells, using Caco-2 cell monolayers, were investigated and compared with those of chitosan hydrochloride and chitosan glutamate. Transepithelial electrical resistance (TEER) measurements at pH 6.20 revealed that all these polymers (0.25-1.5% w/v) caused an immediate and pronounced lowering in TEER values in the order chitosan hydrochloride (84% reduction after 2 h incubation) > chitosan glutamate (60% reduction) > TMC (24% reduction) at 0.25% w/v concentrations. At higher concentrations (up to 2.5% w/v), TMC was able to decrease the TEER further. Similar results were obtained in transport studies, using the hydrophilic radioactive markers, [14C]-mannitol (MW 182.2) and [14C]-polyethylene glycol 4000 (PEG-4000, MW 4000). Large increases in the permeation of these markers were found. The transport of [14C]-mannitol was increased 34-fold (chitosan hydrochloride), 25-fold (chitosan glutamate) and 11-fold (TMC) at 0.25% w/v concentrations. Further increases in the permeation of both markers were found at higher concentrations of TMC. Due to its quaternary structure, TMC is better soluble than the other chitosan salts, and its higher solubility may compensate for its lesser effectivity at similar concentrations. It is also soluble at pH 7.40, where the chitosan salts are insoluble and therefore ineffective. No deleterious effects to the cells could be demonstrated with trypan blue exclusion studies and confocal laser scanning microscopy (CLSM). CLSM confirmed that these polymers increase the transport of large hydrophilic compounds (using the fluorescent markers FD-4, MW 4400 and FD-20, MW 19,600) through opening of tight junctions to allow for paracellular transport. It is concluded from this study that the charge, charge density and the structural features of chitosans and chitosan derivatives are important factors determining their potential use as absorption enhancers.

Biological Transport↗

PubMed1998

Efficacy, safety and mechanism of cyclodextrins as absorption enhancers in nasal delivery of peptide and protein drugs.

Cyclodextrins are used in nasal drug delivery as absorption enhancing compounds to increase the intranasal bioavailability of peptide and protein drugs. The most effective cyclodextrins in animal experiments are the methylated derivatives, dimethyl-beta-cyclodextrin and randomly methylated beta-cyclodextrin, which are active at low concentrations ranging between 2% and 5%. However, large species differences between rats, rabbits and humans exist for the nasal absorption enhancement by cyclodextrins. Based on toxicological studies of the local effects of cyclodextrins on the nasal mucosa dimethyl-beta-cyclodextrin and randomly methylated beta-cyclodextrin are considered safe nasal absorption enhancers. Their effects were quite similar to controls (physiological saline), but smaller than those of the preservative benzalkonium chloride in histological and ciliary beat frequency studies. In these studies, and in a study of the release of marker compounds after nasal administration, methylated beta-cyclodextrins were less toxic than sodium glycocholate, sodium taurodihydrofusidate, laureth-9 and L-alpha-phosphatidylcholine. Systemic toxicity after nasal cyclodextrin administration is not expected, because very low doses of cyclodextrins are administered and only very small amounts are absorbed. The mechanism of action of cyclodextrins may be explained by their interaction with the nasal epithelial membranes and their ability to transiently open tight junctions.

Absorption↗

PubMed1997

Electroperturbation of the human skin barrier in vitro: II. Effects on stratum corneum lipid ordering and ultrastructure.

In transdermal iontophoresis, drugs can be driven across the skin by electrorepulsion, but their transport can also be enhanced by electrical perturbation of the skin barrier. Our objective was to study perturbing effects of electrical current on human stratum corneum lipid fine structure combining techniques including freeze-fracture electron microscopy. Human stratum corneum was subjected to pulsed constant currents, varying from 0.013-13 mA.cm-2. The voltage across the stratum corneum was high-frequency-sampled and s.c. impedence values derived from it. Upon termination of the current, skin samples were rapidly frozen and processed for freeze-fracture electron microscopy or subjected to X-ray diffraction analysis. Initially a rapid decrease of the resistance and, overall, a rapid increase of the capacitances was observed; generally, these effects became more pronounced with increasing current density. Wide- and small-angle X-ray diffractograms of human stratum corneum exposed for 1 h to the highest current indicated a disordering of both the lateral packaging arrangement and long-range lamellar stacking of the intercellular lipids of stratum corneum. Furthermore, an increase in the stratum corneum hydration level as a result of electrical current application was observed. On electron micrographs of freeze-fracture replicas of human stratum corneum, exposed for 1 h to current densities between 0.013 and 13 mA.cm-2, perturbations of the intercellular lipid structure were observed in accordance with the results of X-ray diffraction; these perturbations aggravated with increasing current density. Together, the data suggest that both the lateral and the longitudinal disordering of the intercellular lipids observed with X-ray diffraction may be responsible for the appearance of perturbed structures observed with freeze-fracture electron microscopy. The lipid disordering may be due to polarization of the lipid head groups induced by the electrical field, followed by mutual repulsion.

Adult↗

PubMed1997

Simplified solid-phase extraction method for determination of dihydroergotamine in rabbit and human serum using high-performance liquid chromatography with fluorescence detection.

A rapid, selective and sensitive method for the determination of dihydroergotamine (DHE) in serum was developed. Dihydroergocristine (DHEC) was used as an internal standard. Human and rabbit serum samples were extracted using commercial solid-phase cyano (CN) columns. Proteins were washed from these columns with pure acetonitrile, resulting in clean extracts. Extracts were subsequently separated by HPLC in an isocratic way, using a reversed-phase C18 analytical column. Fluorometric detection was performed at excitation and emission wavelengths of 277 and 348 nm, respectively. Calibration curves with amounts of DHE ranging from 2 to 32 ng, were linear. The limit of detection found for DHE was 0.2 ng, extracted from 0.5 ml rabbit or from 2.5 ml human serum. The limit of quantification in serum of both species was 0.7 ng. The method has been shown to be suitable for monitoring DHE in serum during pharmacokinetic studies in rabbits.

Analgesics, Non-Narcotic↗

PubMed1997

Nasal absorption of dihydroergotamine from liquid and powder formulations in rabbits.

Nasal drug delivery is an interesting route of administration for dihydroergotamine in migraine therapy. The currently available formulation contains dihydroergotamine at 4 mg/mL. For a nasal dose of 2 mg, a volume of 0.5 mL has to be administered, which sometimes leads to spillage of the formulation. The aim of the present study was to develop a nasal spray with a dihydroergotamine concentration of 10 mg/mL. To increase the solubility and stability of dihydroergotamine, randomly methylated beta-cyclodextrin was used. Liquid formulations and lyophilized powders of dihydroergotamine and randomly methylated beta-cyclodextrin were prepared. The liquid and powder formulations were compared by determining their pharmacokinetics and absolute bioavailability after nasal administration in rabbits. Nasal sprays were significantly more effective than drops in increasing the nasal bioavailability of dihydroergotamine, but the amount of randomly methylated beta-cyclodextrin in liquid sprays did not significantly alter the nasal absorption. For powder formulations, the dihydroergotamine absorption was dependent on the amount of methylated beta-cyclodextrin and powder volume, and the nasal bioavailability from the optimal powder was slightly, but not significantly, higher than that for liquids. In conclusion, the formulations investigated are a substantial improvement of the current commercial formulation, not only because the spray volume of the liquid spray can be reduced 2.5 times, but also because of the increased stability of liquid and powder sprays with randomly methylated-beta-cyclodextrin.

Absorption↗

PubMed1997

N-trimethyl chitosan chloride as a potential absorption enhancer across mucosal surfaces: in vitro evaluation in intestinal epithelial cells (Caco-2).

PURPOSE: Previous studies have established that chitosan hydrochloride and glutamate are potent absorption enhancers for large hydrophilic compounds across mucosal surfaces. However, these compounds lack solubility at neutral pH values. A partially quaternized and well-soluble derivative of chitosan, N-trimethyl chitosan chloride, was synthesized and the effects of this polymer on the transepithelial electrical resistance and permeability of intestinal epithelial cells were investigated in vitro. METHODS: N-trimethyl chitosan chloride was synthesized by reductive methylation and characterized with NMR. The effect of this polymer (1.0-2.5% w/v) on the transepithelial electrical resistance of intestinal epithelial cells, using Caco-2 cell monolayers, was investigated. Permeation of the hydrophilic model compounds [14C]-mannitol (MW 182.2), FITC-Dextran (MW 4400) and the peptide drug buserelin (MW 1299.5), in the presence of N-trimethyl chitosan chloride (1.5-2.5% w/v), was followed for 3 hours. The transport process of the fluorescent marker, FITC-Dextran 4400, across the cell monolayers was visualised with confocal laser scanning microscopy. Viability of the cells was checked with the trypan blue exclusion technique. RESULTS: N-trimethyl chitosan chloride was found to be a perfectly water-soluble, partially quaternized (about 12%) derivative of chitosan. This polymer (1.5-2.5% w/v) caused a pronounced and immediate reduction (25-85%) in the transepithelial electrical resistance of Caco-2 cells. Large increases in the transport rate of [14C]-mannitol (32-60 fold), FITC-Dextran 4400 (167-373 fold) and buserelin (28-73 fold) were demonstrated. Confocal laser scanning microscopy confirmed that N-trimethyl chitosan chloride opens the tight junctions of intestinal epithelial cells to allow increased transport of hydrophilic compounds through the paracellular transport pathway. No deleterious effects to the cells could be demonstrated with trypan blue. CONCLUSIONS: The potential use of N-trimethyl chitosan chloride as an absorption enhancer across mucosal surfaces could be an important contribution towards the development of effective delivery systems for hydrophilic drugs.

Biological Transport↗