New insights on the effects of blend composition on the biodegradation and permeability of Inulin-Eudragit RS film coatings for colon drug delivery

Inulin has been applied in Inulin-Eudragit RS (Inu-ERS) coatings as the component responsible for degradation by human microbiota. However, studies on how bacterial enzymes can degrade polysaccharides like inulin imbedded in water insoluble polymers like Eudragit RS are still elusive. The present work aims at elucidating the complex process of enzyme triggered biodegradation of inulin with various molecular weights in isolated films with Eudragit RS. The ratio of inulin to Eudragit RS was varied to create films with different degree of hydrophilicity. The phase behavior study revealed that blends of inulin and Eudragit RS are phase separated systems. The film permeability was studied by determination of the permeability coefficient of caffeine and the fraction of inulin that was released from the films in a buffer solution with or without inulinase was quantified. Together with the morphology characterization of the Inu-ERS films with and without incubation in the enzyme solution, these results suggest that the action of the enzyme was only limited to the fraction of inulin released in the buffer solution. Inulin fully embedded in the Eudragit RS matrix was not degraded. The permeation of the model drug caffeine occurred in the phase-separated film as a result of pores formed as a consequence of inulin release. The inulin to Eudragit RS blend ratio and the molecular weight of inulin affected the percolation threshold, the release of inulin, the morphology of the film formed thereafter and the connectivity of the formed water channels, thus influencing the drug permeation properties.

Ammonio Methacrylate Copolymer (Type B)-Diltiazem Interactions in Solid Dispersions and Microsponge Drug-Delivery Systems

This paper presents a complex analytical study on the distribution, solubility, amorphization, and compatibility of diltiazem within the composition of Eudragit RS 100-based particles of microspongeous type. For this purpose, a methodology combining attenuated total reflectance Fourier transform infrared (ATR-FTIR) absorption spectroscopy, differential scanning calorimetry (DSC), scanning electron microscopy with energy-dispersive X-ray microanalysis (SEM-EDX), and in vitro dissolution study is proposed. The correct interpretation of the FTIR and drug-dissolution results was guaranteed by the implementation of two contrasting reference models: physical drug–polymer mixtures and casting-obtained, molecularly dispersed drug–polymer composites (solid dispersions). The spectral behavior of the drug–polymer composites in the carbonyl frequency (νCO) region was used as a quality marker for the degree of their interaction/mutual solubility. A spectral-pattern similarity between the microsponge particles and the solid dispersions indicated the molecular-type dispersion of the former. The comparative drug-desorption study and the qualitative observations over the DSC and SEM-EDX results confirmed the successful synthesis of a homogeneous coamorphous microsponge-type formulation with excellent drug-loading capacity and “controlled” dissolution profile. Among them, the drug-delivery particles with 25% diltiazem content (M-25) were recognized as the most promising, with the highest population of drug molecules in the polymer bulk and the most suitable desorption profile. Furthermore, an economical and effective analytical algorithm was developed for the comprehensive physicochemical characterization of complex delivery systems of this kind.

Application of inulin/Eudragit RS in 5-ASA pellet coating with tuned, sustained-release feature in an animal model of ulcerative colitis

A tunable release of 5-aminosalicylic acid (5-ASA) could bring therapeutic benefits in the treatment of inflammatory bowel disease (IBD). A 3² factorial design was used to achieve a tuned delivery of 5-ASA pellets in the small and large intestine using a coating composed of inulin/Eudragit RS (RS). The ratio of inulin/RS and coating level were independent variables while the dependent variables were the percent of drug release at pH 1.2 in 2 h and total release of drug in 10 h at pH 6.8. 5-ASA release from pellets was examined at different pH levels and the therapeutic efficacy of the optimum pellets was compared to 5-ASA pellets of Pentasa in rats with ulcerative colitis. The inulin/RS of 18/82 at a coating level of 16% was found to be the optimum for delivery of the drug to the small and large intestine. The coated pellets offered a superior therapeutic outcome compared to uncoated pellets and Pentasa in terms of colitis activity index (CAI), and the colon's tissue enzymes of GSH and MDA. The optimum coating composed of inulin and RS could offer a tuned sustained release of 5-ASA throughout the small and large intestine with the sensitivity of drug release to microbial degradation.

Poloxamer 188-Coated Ammonium Methacrylate Copolymer Nanocarriers Enhance Loperamide Permeability across Pgp-Expressing Epithelia

Loperamide is a μ-opioid agonist with poor gastrointestinal absorption, mainly because of its modest aqueous solubility and being a P-glycoprotein (Pgp) efflux substrate. Nevertheless, studies associated with therapeutic effects strongly suggest that loperamide holds potential pharmacological advantages over traditional μ-opioid agonists commonly used for analgesia. Thus, in this Communication, we assessed in MDCK-hMDR1 cell lines the effects over loperamide uptake and efflux ratio, when loaded into Eudragit RS (ERS) nanocarriers coated with poloxamer 188 (P188). ERS was chosen for enhancing loperamide aqueous dispersibility and P188 as a potential negative Pgp modulator. In uptake assays, it was observed that Pgp limited the accumulation of loperamide into cells and that preincubation with P188, but not coincubation, led to increasing loperamide uptake at a similar extent of Pgp pharmacological inhibition. On the other hand, the efflux ratio displayed no alterations when Pgp was pharmacologically inhibited, whereas ERS/P188 nanocarriers effectively enhanced loperamide uptake and absorptive transepithelial transport. The latter suggests that loperamide transport across cells is significantly influenced by the presence of the unstirred water layer (UWL), which could hinder the visualization of Pgp-efflux effects during transport assays. Thus, results in this work highlight that formulating loperamide into this nanocarrier enhances its uptake and transport permeability.

Design of pressure-sensitive adhesive suitable for the preparation of transdermal patches by hot-melt printing

This work aimed to design low-melting pressure sensitive adhesives and to demonstrate the feasibility of the preparation of (trans)dermal patches by hot-melt ram extrusion printing. This approach allows defining both the geometry of (trans)dermal patch and the drug strength easily according to patient needs. The preparation steps are the mixing of a poly-ammonium methacrylate polymer (i.e. Eudragit RL and RS) with a suitable amount of plasticizer (triacetin or tributyl citrate) and drug (ketoprofen or nicotine), the melting in the ram extruder, and the printing on the backing layer foil. The formulations were characterized in terms of rheological and adhesive properties, in vitro drug release and skin permeation profiles. The (trans)dermal patches made of Eudragit RL or Eudragit RS plasticized with the 40% triacetin could be printed at 90 °C giving formulations with suitable adhesive properties and without cold flow after 1 month of storage at 40 °C. Furthermore, the overall results showed that the performances of printed (trans)dermal patches overlapped those made by solvent casting, suggesting that the proposed solvent-free technology can be useful to treat cutaneous pathologies when the availability of (trans)dermal patches with size and shape that perfectly fit with the skin area affected by the disease improves the safety of the pharmacological treatment.

Reducing Burst Release Effect of Freely Water-Soluble Drug Incorporated into Gastro-Floating Formulation Below HPMC Threshold Concentration Through Interpolymer Complex

Undesired-burst release effect is observed in a freely water-soluble drug formulated into a gastro-floating formulation with effervescent (GFFE) delivery system. In order to address this limitation, interpolymer complex (IPC) of two swellable and non-soluble polymers, poly-ammonium methacrylate and poly-vinyl acetate, was incorporated into hydroxypropyl methyl cellulose (HPMC)-based matrix GFFE. This research studied the effect and interaction of the IPC-HPMC blending on the drug release of GFFE using a freely water-soluble drug, metformin HCl, under different threshold concentration levels and curing effect. The interaction between the IPC and HPMC was characterized using vibrational spectroscopy and thermal analyses under curing and swelling conditions. Anti-solvent followed by lyophilization had better physicochemical and physicomechanic properties than spray dying technique. The interaction was observed by a specific shifting of the vibrational peaks and alteration of the thermal behavior pattern. These effects altered the drug release behavior. Thereafter, the IPC reduced burst release effects in the initial time and during testing, and the IPC improved the HPMC matrix robustness under mechanical stress testing below threshold concentration of HPMC matrix formulated in the GFFE.

When drugs plasticize film coatings: Unusual formulation effects observed with metoprolol and Eudragit RS

Metoprolol tartrate and metoprolol free base loaded pellet starter cores were coated with Eudragit RS, plasticized with 25% triethyl citrate (TEC). The initial drug loading and coating level were varied from 10 to 40 and 0 to 20%, respectively. Drug release was measured in 0.1 N HCl and phosphate buffer pH 7.4. The water uptake and swelling kinetics, mechanical properties and TEC leaching of/from coated pellets and/or thin, free films of identical composition as the film coatings were monitored. The following unusual tendencies were observed: (i) the relative drug release rate from coated pellets increased with increasing initial drug content, and (ii) drug release from pellets was much faster for metoprolol free base compared to metoprolol tartrate, despite its much lower solubility (factor >70). These phenomena could be explained by plasticizing effects of the drug for the polymeric film coatings. In particular: 1) Metoprolol free base is a much more potent plasticizer for Eudragit RS than the tartrate, leading to higher film permeability and overcompensating the pronounced differences in drug solubility. Also, Raman imaging revealed that substantial amounts of the free base migrated into the film coatings, whereas this was not the case for the tartrate. 2) The plasticizing effects of the drug for the film coating overcompensated potential increasing limited solubility effects when increasing the initial drug loading from 10 to 40%. In summary, this study clearly demonstrates how important the plasticization of polymeric controlled release film coatings by drugs can be, leading to unexpected formulation effects.

Role of clove oil in solvent exchange-induced doxycycline hyclate-loaded Eudragit RS in situ forming gel

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Role of clove oil (CO) in doxycycline hyclate (DH)-loaded Eudragit RS (ERS) in situ forming gel (ISG) was investigated.

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CO could solubilize ERS and increase the viscosity of ISG and also minimize DH burst release with sustainable DH release.

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ISGs comprising CO could expel through the 27-gauge needle and transform into matrix depot in simulated crevicular fluid.

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Antimicrobial activities against all test bacterias were increased when increasing CO and N-methyl pyrrolidone (NMP) ratio.

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DH-loaded ERS ISG comprising CO could be used as a local drug delivery system for periodontitis treatment.

Solvent exchange induced in situ forming gel (ISG) is the promising drug delivery system for periodontitis treatment owing to the prospect of maintaining an effective high drug level in the gingival crevicular fluid. In the present study, the influence of clove oil (CO) on the characteristics of doxycycline hyclate (DH)-loaded ISG comprising Eudragit RS (ERS) was investigated including viscosity/rheology, syringeability, in vitro gel formation/drug release, matrix formation/solvent diffusion and antimicrobial activities. CO could dissolve ERS and increase the viscosity of ISG and its hydrophobicity could also retard the diffusion of solvent and hinder the drug diffusion; thus, the minimization of burst effect and sustained drug release were achieved effectively. All the prepared ISGs comprising CO could expel through the 27-gauge needle for administration by injection and transform into matrix depot after exposure to the simulated gingival crevicular fluid. The antimicrobial activities against Staphylococcus aureus, Escherichia coli, Streptococcus mutans and Porphyromonas gingivalis were increased when the ratio of CO and N-methyl pyrrolidone (NMP) was decreased from 1:1 to 1:10 owing to higher diffusion of DH except that for C. albicans was increased as CO amount was higher. Therefore, CO could minimize the burst while prolonging the drug release of DH-loaded ERS ISG for use as a local drug delivery system for periodontitis treatment.

Characterization of Antimicrobial Agent Loaded Eudragit RS Solvent Exchange-Induced In Situ Forming Gels for Periodontitis Treatment

Eudragit RS (ERS), a quaternary polyacrylate positively charged polymer, exhibits a very low permeability and swells in aqueous media independently of pH without dissolving. Owing to its high solubility in N-methyl pyrrolidone (NMP), it was interesting to apply as polymer matrix for solvent-exchanged in situ forming gel. The aim of this research was to prepare in situ forming gels from ERS to deliver the antimicrobial agents (doxycycline hyclate, metronidazole, and benzoyl peroxide) for periodontitis treatment. They were evaluated for viscosity and rheology, gel formation, syringeability, drug release, and antimicrobial activities. The solvent exchange between NMP and an external aqueous simulated gingival crevicular fluid stimulated the dissolved ERS transforming into the opaque rigid gel. Antimicrobial agent loaded ERS systems exhibited Newtonian flow with acceptable syringeability. The higher-loaded ERS promoted the more prolongation of drug release because of the retardation of water diffusion into the precipitated matrix. Antimicrobial activities against Staphylococcus aureus, Escherichia coli, Candida albicans, Streptococcus mutans, and Porphyromonas gingivalis depended on type of drugs and test microorganisms. Doxycycline hyclate loaded ERS systems showed these activities greater than the others; however, all of them could inhibit all test microorganisms. Thus, the solvent exchange-induced in situ forming gels comprising ERS-antimicrobial drugs exhibited potential use as localized delivery systems for periodontitis treatment.

Quality by Design Based Fabrication of Iron Oxide Induced Mucoadhesive Microspheres for Enhanced Bioavalibility of Cinnarizine

BACKGROUND

The study was aimed to enhance the mucoadhesive potential of Eudragit RS 100 and RL 100 using iron oxide.

METHODS

Microspheres of Eudragit RS/RL100, containing cinnarizine, were prepared by emulsification solvent evaporation technique employing 32 full factorial design. Eudragit RS or RL (X1) and iron oxide (X2) concentrations were the independent variables. Particle size, entrapment efficiency, mucoadhesion, zeta potential and t90% were the response variables. Microspheres when characterized by FTIR-ATR and DSC confirm entrapment of drug.

RESULTS

SEM analysis of microspheres exhibits roughness/micropores responsible for drug release. Particle size of Eudragit RS and Eudragit RL microspheres was found to increase from 275.60±2.68 to 438.72±22.73 nm and 283.14±1.95 to 475.55±29.66 nm. Incorporation of iron oxide increases zeta potential from 0.88±0.18 to 10.74±1.78 mV and 1.12±0.11 to 14.44±2.44 mV for Eudragit RS and RL microspheres, respectively. Highest mucoadhesion and zeta potential were obtained when 4.5% w/v of X1 and 20% w/v of X2 were used in the formulation of microspheres.

CONCLUSION

The r2 values were significantly higher (P < 0.01) for the Langmuir equation as compared to Freundlich equation, indicating the involvement of electrostatic forces in the specific adsorption of mucin on to Eudragit microspheres. In vivo study indicates 2.5 to 3 times increased bioavailabity of cinnarizine through mucoadhesive microspheres.