Factors affecting the bioadhesive property of tablets consisting of hydroxypropyl cellulose and carboxyvinyl polymer

Interpolymer complexes of carbopol® 971 and poly(2-ethyl-2-oxazoline): Physicochemical studies of complexation and formulations for oral drug delivery

Carbopol® 971 and poly(2-ethyl-2-oxazoline) form hydrogen-bonded interpolymer complexes in aqueous solutions and their complexation is strongly dependent on solution pH. This work investigated the complexation between these polymers in aqueous solutions. The compositions of interpolymer complexes as well as the critical pH values of complexation were determined. The structure of these complexes was studied in solutions using transmission electron microscopy and in solid state using elemental analysis, FTIR spectroscopy and differential scanning calorimetry. Solid compacts were prepared based on interpolymer complexes and physical blends of these polymers and their swelling behaviour was studied in aqueous solutions mimicking the fluids present in the gastrointestinal tract. These materials were used to prepare oral formulations of mesalazine and its release from solid matrices was studied in vitro. It was demonstrated that the complexation between Carbopol® 971 and poly(2-ethyl-2-oxazoline) has a profound effect on the drug release from matrix tablets.

Hydrogen-bonded complexes and blends of poly(acrylic acid) and methylcellulose: nanoparticles and mucoadhesive films for ocular delivery of riboflavin

Poly(acrylic acid) (PAA) and methylcellulose (MC) are able to form hydrogen-bonded interpolymer complexes (IPCs) in aqueous solutions. In this study, the complexation between PAA and MC is explored in dilute aqueous solutions under acidic conditions. The formation of stable nanoparticles is established, whose size and colloidal stability are greatly dependent on solution pH and polymers ratio in the mixture. Poly(acrylic acid) and methylcellulose are also used to prepare polymeric films by casting from aqueous solutions. It is established that uniform films can be prepared by casting from polymer mixture solutions at pH 3.4-4.5. At lower pHs (pH < 3.0) the films have inhomogeneous morphology resulting from strong interpolymer complexation and precipitation of polycomplexes, whereas at higher pHs (pH 8.3) the polymers form fully immiscible blends because of the lack of interpolymer hydrogen-bonding. The PAA/MC films cast at pH 4 are shown to be non-irritant to mucosal surfaces. These films provide a platform for ocular formulation of riboflavin, a drug used for corneal cross-linking in the treatment of keratoconus. An in vitro release of riboflavin as well as an in vivo retention of the films on corneal surfaces can be controlled by adjusting PAA/MC ratio in the formulations.

Polymeric complexes of lidocaine hydrochloride with poly(acrylic acid) and poly(2-hydroxyethyl vinyl ether)

The specific interactions of local anesthetic lidocaine hydrochloride with poly(acrylic acid) and poly(2-hydroxyethyl vinyl ether), as well as in a triple system composed of the drug and both polymers, have been studied in aqueous solutions by viscometric, turbidimetric, potentiometric, and FTIR spectroscopic methods. The mechanism of the drug binding to the polymers and the structures of the polycomplexes formed are clarified.

Bioadhesive sulfacetamide sodium microspheres: evaluation of their effectiveness in the treatment of bacterial keratitis caused by Staphylococcus aureus and Pseudomonas aeruginosa in a rabbit model

The aim of this study was to prepare bioadhesive sulfacetamide sodium (SA) microspheres to increase their residence time on the ocular surface and to enhance their treatment efficacy on ocular keratitis. Microspheres were fabricated by spray drying method using mixture of polymers such as pectin, polycarbophil and hydroxypropylmethyl cellulose (HPMC) at different ratios. The particle size and distribution, morphological characteristics, thermal behavior, encapsulation efficiency, mucoadhesion and in vitro drug release studies on formulations have been investigated. After optimisation studies, SA-loaded polycarbophil microsphere formulation with polymer:drug ratio of 2:1 was found to be the most suitable for ocular application and used in in vivo studies. In vivo studies were carried out on New Zealand male rabbit eyes with keratitis caused by Pseudomonas aeruginosa and Staphylococcus aureus. Sterile microsphere suspension in light mineral oil was applied to infected eyes twice a day. Plain SA suspension was used as a positive control. On 3rd and 6th days of the antimicrobial therapy, the eyes were examined in respect to clinical signs of infection (blepharitis, conjunctivitis, iritis, corneal oedema and corneal infiltrates) which are the main symptoms of bacterial keratitis and then cornea samples were counted microbiologically. The rabbit eyes treated with microspheres demonstrated significantly lower clinical scores than those treated with SA alone. A significant decrease in the number of viable bacteria in eyes treated with microspheres was observed in both infection models when compared to those treated with SA alone. In conclusion, in vitro and in vivo studies showed that SA-loaded microspheres were proven to be highly effective in the treatment of ocular keratitis.

Studies on formulation development of mucoadhesive sustained release itraconazole tablet using response surface methodology

The purpose of this research was to prepare and evaluate sustained release mucoadhesive tablets of Itraconazole. It is practically insoluble in aqueous fluids hence its solid dispersion with Eudragit E100 was prepared by spray drying. This was formulated in matrix of hydrophilic mucoadhesive polymers Carbopol 934P (CP) and Methocel K4M (HPMC). The formulation was optimized using a 3(2) factorial design. Amounts of CP and HPMC were taken as formulation variables for optimizing response variables i.e. mucoadhesion and dissolution parameters. The optimized mucoadhesive formulation was orally administered to albino rabbits, and blood samples collected were used to determine pharmacokinetic parameters. The solid dispersion markedly enhanced the dissolution rate of itraconazole. The bioadhesive strength of formulation was found to vary linearly with increasing amount of both polymers. Formulations exhibited drug release fitting Peppas model with value of n ranging from 0.61 to 1.18. Optimum combination of polymers was arrived at which provided adequate bioadhesive strength and fairly regulated release profile. The experimental and predicted results for optimum formulations were found to be in close agreement. The formulation showed C (max) 1898 +/- 75.23 ng/ml, t (max) of the formulation was 2 h and AUC was observed to be 28604.9 ng h/ml.

Polyelectrolyte complexes of Eudragit l30 d-55 and gelatin: antinociceptive activity of entrapped piroxicam

The electrostatic interaction between oppositely charged polyelectrolytes leads to the formation of polyelectrolyte complexes, which are of considerable interest because of their potential applications as both drug carriers or surface modifying agents. In this study, in vitro and in vivo studies were carried out on polyelectolyte complexes formulated with Eudragit L30 D-55 and gelatin. The complexes of Eudragit L30 D-55 and gelatin were formulated by nonstoichiometric method. The polyelectrolyte complexes formulated were then granulated and evaluated by percentage yield, particle size, and swelling behavior. The pharmacodynamic effects of piroxicam entrapped in the complexes were determined using healthy rats. Results showed that gelatin and Eudragit L30 D-55 formed polyelectrolyte complexes that prolonged the antinociceptive effects of piroxicam in experimental rats. The performance of the polyelectrolyte complexes could be stated in the following descending rank order: 1:1 > 2:1 > 1:2 ratios of Eudragit L30 D-55 and gelatin. Nonstoichiometric interactions of gelatin and Eudragit L30 D-55 could yield matrices with adequate characteristics for the formulation of sustained release systems of drugs.

Formulation and evaluation of lactoferrin bioadhesive tablets

For the treatment of chronic inflammation in the oral cavity, we attempted to develop bioadhesive tablets of bovine lactoferrin (B-LF) which has antibacterial properties and immune regulatory functions. B-LF tablets containing pectin, tamarind gum or carboxymethylcellulose (CMC) were prepared by direct compression. Tablets consisting of B-LF, pectin and xylitol passed through 60- or 100-mesh sieves were also prepared. The tablets containing CMC had insufficient bioadhesive force. Although the tablets containing tamarind gum showed the longest residence time in the oral cavity, an unpleasant taste gradually developed. The tablets containing pectin showed the highest value of bioadhesive force and the taste was acceptable. The characteristics of the B-LF tablets were improved by adding an appropriate amount of xylitol and using the ingredients sieved by a 100-mesh sieve. The therapeutic effect was evaluated by using rats with an ulcer on the oral mucosa. In the present study, swelling on the periphery of the ulcer was observed after administration of the B-LF tablets, and then the ulcer has reduced overall.

Design of Mucoadhesive Polymeric Films Based on Blends of Poly(acrylic acid) and (Hydroxypropyl)cellulose

Mixing of aqueous solutions of poly(acrylic acid) and (hydroxypropyl)cellulose results in formation of hydrogen-bonded interpolymer complexes, which precipitate and do not allow preparation of homogeneous polymeric films by casting. In the present work the effect of pH on the complexation between poly(acrylic acid) and (hydroxypropyl)cellulose in solutions and miscibility of these polymers in solid state has been studied. The pH-induced complexation-miscibility-immiscibility transitions in the polymer mixtures have been observed. The optimal conditions for preparation of homogeneous polymeric films based on blends of these polymers have been found, and the possibility of radiation cross-linking of these materials has been demonstrated. Although the gamma-radiation treatment of solid polymeric blends was found to be inefficient, successful cross-linking was achieved by addition of N,N'-methylenebis(acrylamide). The mucoadhesive potential of both soluble and cross-linked films toward porcine buccal mucosa is evaluated. Soluble films adhered to mucosal tissues undergo dissolution within 30-110 min depending on the polymer ratio in the blend. Cross-linked films are retained on the mucosal surface for 10-40 min and then detach.

Formulation and in vitro evaluation of prednisolone buccoadhesive tablets

In this research, the effect of mucoadhesive polymers such as hydroxyl propyl methyl cellulose (HPMC) with viscosity grade 60 and 500 mPas, sodium carboxy methyl cellulose (NaCMC) and carbopol 934 (Cp 934) alone or in combination with each other on the release profile of prednisolone was studied and mucoadhesion strength of these buccoadhesive formulations was evaluated. The results showed that the release of prednisolone from HPMC with viscosity grade 60 mPas and Cp 934 alone was fast and their mucoadhesion strengths was low. On the other hand, the release rates of prednisolone from the HPMC viscosity grade 500 mPas and NaCMC and mucoadhesion strengths were moderate and suitable. The results showed that with different blends of HPMC viscosity grade 500 mPas or NaCMC and Cp 934 with increasing in HPMC or NaCMC/Cp 934 ratio a remarkable decrease in the rate of drug release and an appreciable increase in the mucoadhesion strength was observed. Except from the formulations prepared with HPMC viscosity grade 60 and 500 mPas, other formulation had more fluctuations in release profiles and their kinetics of release were not fitted to zero order model.

Adhesive tablet effective for treating canker sores in humans

A new mucoadhesive tablet, which releases natural active agents for pain reduction and rapid healing of canker sores, has been prepared and characterized. Adhesive tablets were prepared by compression molding of mixed powders of crosslinked polyacrylic acid and hydroxypropyl cellulose, absorbed with citrus oil and magnesium salt. The rate of tablet erosion and the rates of citrus oil and magnesium release were determined as well as the adhesiveness of the tablet using bovine gingival tissue and an Instron tensiometer. A clinical trial was conducted on 248 volunteers who had canker sores. Tablets adhere well to the mucosal tissue and gradually erode for 8 h releasing the citrus oil in a zero-order pattern whereas the magnesium is released during a period of 2 h. Both experimental and plain tablets were effective in reducing pain and decreasing healing time (p < 0.05) without adverse side effects. However, the tablets loaded with active agents were more effective.

Novel mucoadhesive buccal formulation containing metronidazole for the treatment of periodontal disease

Mucoadhesive tablets using different mixture of cellulose and polyacrylic derivatives were prepared in order to obtain new formulations containing metronidazole for periodontal disease treatment. All tablets were characterized by swelling studies, ex vivo and in vivo mucoadhesive time, ex vivo mucoadhesion force, in vitro and in vivo release. The best mucoadhesive performance and the best in vitro drug release profile were achieved by using hydroxyethyl cellulose (HEC) and carbomer 940 2:2 ratio. The chosen tablet, containing 20 mg of metronidazole, performed 12 h drug sustained release with buccal concentrations always higher than its MIC.

Complexation Between PVP and Gantrez Polymer and Its Effect on Release and Bioadhesive Properties of the Composite PVP/Gantrez Films

Complexation between poly(methyl vinyl ether-maleic anhydride) copolymer (Gantrez AN 169) and polyvinylpyrrolidone (PVP K-90D) in aqueous solutions were investigated using a viscometric method and Raman spectroscopy. The composite films with different weight ratios of PVP to Gantrez were prepared in the presence of N-methyl-2-pyrrolidone. The release profiles of diclofenac sodium (DS) from these films were determined and the bioadhesive properties measured. An interpolymer complex was formed through hydrogen bonding between the carbonyl groups of PVP and the hydroxyl groups of Gantrez. The formation of interpolymer hydrogen bonds reduced the interaction of the polymers with water molecules, thus resulting in a lower solubility of the complex in water and a further retarded release of DS from the composite films. The interpolymer complexation was also found to increase the bioadhesive properties of the composite films to a silicone elastomer substrate. The complexation of PVP and the Gantrez copolymer in the composite films was a critical factor affecting the release of DS from the films and the bioadhesive properties of the films.

Release phenomena of insulin from an implantable device composed of a polyion complex of chitosan and sodium hyaluronate

An implant controlled-release system for protein drug delivery based on a polyion complex device composed of chitosan (CS) and sodium hyaluronate (HA) was investigated. The conditions which generated the greatest amount of the polyion solid complex were studied to ascertain the formation of polyion complex between CS and HA. The greatest amount of the polyion complex was formed at the weight ratio of 3 to 7 (CS:HA) at pH 3.5. Furthermore, the CS-HA pellets were prepared and then drug release from CS-HA pellets was evaluated using insulin as a model drug. The results demonstrated that the insulin release from CS-HA pellets was markedly influenced by both the change in the polymer mixing ratio and the total pellet weight, whereas the compression pressure did not affect the release significantly. An artificial neural network (ANN) and biharmonic spline interpolation (HSI) were employed to predict the actual relation between causal factors and the release rate constant of insulin. Although both the ANN and HSI successfully represented a non-linear relationship between the formulation factors and the release rate constant, HSI methodology gave a better estimation than that of the ANN.

Mucoadhesive nanoparticulate systems for peptide drug delivery

This chapter describes the preparation of and methods for evaluating mucoadhesive nanoparticulate systems, including liposomes and polymeric nanoparticles. Mucoadhesive ability is conferred on the particulate systems by coating their surface with mucoadhesive polymers such as chitosan and Carbopol. The feasibility of this surface modification was confirmed by measuring the zeta potential. Several methods of evaluating the mucoadhesive properties of particulate systems have been reported in the literature. We have also developed some novel evaluation procedures including a particle counting method using a Coulter counter for polymer-coated liposomes. The mucoadhesive properties of the polymer-coated liposomes and polymeric nanoparticles were confirmed by means of these mucoadhesion tests. In applying these mucoadhesive nanoparticles to the oral and pulmonary administration of peptide drugs, more effective and prolonged action was observed in comparison with non-coated systems, thereby confirming the usefulness of mucoadhesive nanoparticulate systems for the delivery of peptide drugs.

The biopharmaceutical aspects of nasal mucoadhesive drug delivery

Nasal drug administration has frequently been proposed as the most feasible alternative to parenteral injections. This is due to the high permeability of the nasal epithelium, allowing a higher molecular mass cut-off at approximately 1000 Da, and the rapid drug absorption rate with plasma drug profiles sometimes almost identical to those from intravenous injections. Despite the potential of nasal drug delivery, it has a number of limitations. In this review, the anatomy and physiology of the nasal cavity, as well as ciliary beating and mucociliary clearance as they relate to nasal drug absorption, are introduced. The rationale for nasal drug delivery and its limitations, some factors that influence nasal drug absorption, and the experimental models used in nasal drug delivery research are also reviewed. Nasal mucoadhesion as a promising method of nasal absorption enhancement is discussed, and factors that influence mucoadhesion, as well as safety of nasal mucoadhesive drug delivery systems are reviewed in detail. Nasal drug administration is presently mostly used for local therapies within the nasal cavity. Anti-allergic drugs and nasal decongestants are the most common examples. However, nasal drug administration for systemic effects has been practised since ancient times. Nasally-administered psychotropic drugs by native Americans, the use of tobacco snuffs, and nasal administration of illicit drugs such as cocaine are all well known (Illum & Davis 1992). Nowadays, the nasal cavity is being actively explored for systemic administration of other therapeutic agents, particularly peptides and proteins (Illum 1992; Edman & Björk 1992), as well as for immunization purposes (Lemoine et al 1998). To better understand the basis for nasal drug absorption and factors that can influence it, a brief review of the anatomy and physiology of the nose is appropriate.

Potential applications of carbomer in oral mucoadhesive controlled drug delivery system: a review

Carbomers are extensively being used in controlled drug delivery systems (CDDS). They are also finding numerous applications in oral mucoadhesive drug delivery because of their ability to interact with the mucus glycoprotein and to remain localized to a specific site. The present review aims at giving an insight into the potential application of carbomers in mucoadhesive CDDS. This review deals with the physicochemical properties of carbomers and various mechanisms of mucoadhesion. The mechanism for the release of the drug, both water soluble and water insoluble, is discussed. The use of carbomers in oral delivery of peptides or protein-based drugs is also covered.

Effect of Carbopol and polyvinylpyrrolidone on the mechanical, rheological, and release properties of bioadhesive polyethylene glycol gels

This study examined the mechanical (hardness, compressibility, adhesiveness, and cohesiveness) and rheological (zero-rate viscosity and thixotropy) properties of polyethylene glycol (PEG) gels that contain different ratios of Carbopol 934P (CP) and polyvinylpyrrolidone K90 (PVP). Mechanical properties were examined using a texture analyzer (TA-XT2), and rheological properties were examined using a rheometer (Rheomat 115A). In addition, lidocaine release from gels was evaluated using a release apparatus simulating the buccal condition. The results indicated that an increase in CP concentration significantly increased gel compressibility, hardness, and adhesiveness, factors that affect ease of gel removal from container, ease of gel application onto mucosal membrane, and gel bioadhesion. However, CP concentration was negatively correlated with gel cohesiveness, a factor representing structural reformation. In contrast, PVP concentration was negatively correlated with gel hardness and compressibility, but positively correlated with gel cohesiveness. All PEG gels exhibited pseudoplastic flow with thixotropy, indicating a general loss of consistency with increased shearing stress. Drug release T50% was affected by the flow rate of the simulated saliva solution. A reduction in the flow rate caused a slower drug release and hence a higher T50% value. In addition, drug release was significantly reduced as the concentrations of CP and PVP increased because of the increase in zero-rate viscosity of the gels. Response surfaces and contour plots of the dependent variables further substantiated that various combinations of CP and PVP in the PEG gels offered a wide range of mechanical, rheological, and drug-release characteristics. A combination of CP and PVP with complementary physical properties resulted in a prolonged buccal drug delivery.

Studies on applicability of press-coated tablets using hydroxypropylcellulose (HPC) in the outer shell for timed-release preparations

Press-coated tablets, containing diltiazem hydrochloride (DIL) in the core tablet and coated with hydroxypropylcellulose (HPC) as the outer shell, were examined for applicability as timed-release tablets with a predetermined lag time and subsequent rapid drug release phase. Various types of press-coated tablets were prepared using a rotary tabletting machine and their DIL dissolution behavior was evaluated by the JP paddle method. The results indicated that tablets with the timed-release function could be prepared, and that the lag times were prolonged as the viscosity of HPC and the amount of the outer shell were increased. The lag times could be controlled widely by the above method, however, the compression load had little effect. Two different kinds of timed-release press-coated tablets that showed lag times of 3 and 6 h in the in vitro test (denoted PCT(L3) and PCT(L6), respectively) were administered to beagle dogs. DIL was first detected in the plasma more than 3 h after administration, and both tablets showed timed-release. The lag times showed a good agreement between the in vivo and in vitro tests in PCT(L3). However, the in vivo lag times were about 4 h in PCT(L6) and were much shorter than the in vitro lag time. The dissolution test was performed at different paddle rotation speeds, and good agreement was obtained between the in vivo and in vitro lag times at 150 rpm. This suggested that the effects of gastrointestinal peristalsis and contraction should also be taken into consideration for the further development of drug delivery systems.

Interpolymer complexation. I. Preparation and characterization of a polyvinyl acetate phthalate-polyvinylpyrrolidone (PVAP-PVP) complex

Polyvinyl acetate phthalate (PVAP) and polyvinylpyrrolidone (PVP) readily reacted in ethanol and acidic aqueous solutions to produce an insoluble PVAP-PVP complex. The complex has a pK(a) of 3.8. It is practically insoluble in common organic solvents, but dissolves in dimethylsulfoxide, an alkali or ammonical solution, and a 4:1 (v/v) mixture of methylene chloride and methanol. The powder X-ray diffraction analysis revealed the complex to be an amorphous material. The Fourier-transform infrared spectrum of the complex exhibited characteristics carbonyl stretching vibrations at 1724 and 1657 cm(-1) due to phthalate and acetate moieties in PVAP and cyclic amide groups in PVP, respectively, and at 1632 cm(-1) (appeared as a shoulder) due to cyclic amide groups of PVP bound to PVAP. The proton and carbon-13 (solution and solid-state) nuclear magnetic resonance spectra of the complex showed peak profiles that were linear combinations of those of PVAP and PVP. No new peaks appeared and no change in chemical shifts was observed due to complexation. The spectral data suggest that the interaction between PVAP and PVP probably initially involves the formation of hydrogen bonds between carbonyl groups of PVP and carboxylic groups of PVAP at some point of the polymer chains, causing the hydrophilic parts of the two flexible polymer chains strongly hydrophobic. As a result, the two polymer chains coil up into a compact structure and, consequently, precipitate out from the solution as an insoluble complex.

Evaluation of polyoxyethylene homopolymers for buccal bioadhesive drug delivery device formulations

Our objective was to evaluate the application of polyoxyethylene homopolymers in buccal bioadhesive drug (BBD) delivery device formulations. The bioadhesive strength of four different molecular weight (MW) polyoxyethylene polymers was measured by Instron tensile tester using glass plate and bovine sublingual tissue as substrate surfaces. Several BBD device formulations containing polyoxyethylene polymer (MW 7,000,000) were prepared by direct compression and compression molding processes. The prepared BBD devices were evaluated for their elasticity, in vitro adhesion and drug release characteristics. The in vivo bioadhesion characteristics of a placebo compression molded device were examined in 3 adult healthy male beagle dogs. The bioadhesive strength of polyoxyethylene polymers appeared to be directly related to their molecular weights. When bovine sublingual mucosa or a glass plate was used as model mucosal substrate surface, the rank order of bioadhesive strength of different molecular weight polyoxyethylene polymers was similar. The bioadhesive strength of devices prepared by the compression molding process was greater than those prepared by direct compression, but the kinetics of drug release were independent of the process used for the preparation of the devices. The drug release and the bioadhesive strength of the similarly prepared device formulations appeared to be dependent on the drug:polymer ratios. The elasticity of the BBD devices prepared by compression molding was improved by the inclusion of polyisobutylene polymer in the formulations. When adhered to the oral cavity of the dogs, the compression molded placebo BBD device exhibited adhesion for at least 4 hours and appeared to show no signs of local irritation. In conclusion, BBD devices containing polyoxyethylene polymer (MW 7,000,000) can be prepared by direct compression or compression molding process in order to provide controlled drug release to the oral cavity while maintaining appropriate bioadhesive characteristics.

Enteral absorption of insulin in rats from mucoadhesive chitosan-coated liposomes

PURPOSE

The mucoadhesiveness of polymer-coated liposomes was evaluated to develop a novel drug carrier system for oral administration of poorly absorbed drugs such as peptide drugs.

METHODS

Multilamellar liposomes consisting of dipalmitoylphosphati-dylcholine (DPPC)and dicetyl phosphate (DCP) (DPPC: DCP = 8:2 in molar ratio) were coated with chitosan (CS), polyvinyl alcohol having a long alkyl chain (PVA-R) and poly (acrylic acid) bearing a cholesteryl group. The adhesiveness of the resultant polymer-coated liposomes to the rat intestine was measured in vitro by a particle counting method with a Coulter counter. The CS-coated liposomes containing insulin were administered to normal rats and the blood glucose level was monitored.

RESULTS

The existence of polymer layers on the surface of liposomes was confirmed by measuring the zeta potential of liposomes. The CS-coated liposomes showed the highest mucoadhesiveness and the degree of adhesion was dependent on the amount of CS on the surface of the liposomes. The blood glucose level of rats was found to be significantly decreased after administration of the CS-coated liposomes containing insulin. The lowered glucose level was maintained for more than 12h after administration of the liposomal insulin, which suggested mucoadhesion of the CS-coated liposomes in the intestinal tract of the rats.

In vitro and in vivo evaluation of mucoadhesive microspheres prepared for the gastrointestinal tract using polyglycerol esters of fatty acids and a poly(acrylic acid) derivative

Two types of polyglycerol ester of fatty acid (PGEF)-based microspheres were prepared: Carbopol 934P (CP)-coated microspheres (CPC-microspheres) and CP-dispersion microspheres (CPD-microspheres). Comparative studies on mucoadhesion were done with these microspheres and PGEF-based microspheres without CP (PGEF-microspheres). In an in vitro adhesion test, the CPD-microspheres adhered strongly to mucosa prepared from rat stomach and small intestine because each CP particle in the CPD-microsphere was hydrated and swelled with part of it remaining within the microsphere and part extending to the surface serving to anchor the microsphere to the mucus layer. The gastrointestinal transit patterns after administration of the CPD-microspheres and PGEF-microspheres to fasted rats were fitted to a model in which the microspheres are emptied from the stomach monoexponentially with a lag time and then transit through the small intestine at zero-order. Parameters obtained by curve fitting confirmed that the gastrointestinal transit time of the CPD-microspheres was prolonged compared with that of the PGEF-microspheres. MRT in the gastrointestinal tract was also prolonged after administration of the CPD-microspheres compared with that following the administration of the PGEF-microspheres.

Mucoadhesion of copolymers and mixtures containing polyacrylic acid

Water-soluble polymers were synthesized from dextran and polyacrylic acid and their ocular mucoadhesion was evaluated. One series had polyacrylic acid grafted onto the polysaccharide backbone of dextran, and another series had dextran grafted onto the polyacrylic acid backbone. Mucoadhesion of these copolymers was investigated using a tensile apparatus and compared with that of polyacrylic acid/dextran mixtures prepared in different proportions. Whatever the copolymer structure, no synergistic effects were seen and mucoadhesion was not markedly increased compared to dextran. The adhesion of copolymers was the same as that of mixtures having a similar polyacrylic acid content and was always less than that of polyacrylic acid alone. Formation of an interpolymer complex occurred at concentrations up to 60% polyacrylic acid, and only above this value did bioadhesion increase above that of dextran. When this complex was dissociated by neutralization of the carboxyl groups of polyacrylic acid, the mucoadhesion of the copolymers and the mixtures was improved. These experiments demonstrated that copolymers and mixtures of dextran and polyacrylic acid did not produce polymers with improved ocular mucoadhesion.