Encapsulation of poorly soluble basic drugs into enteric microparticles: A novel approach to enhance their oral bioavailability

In Vitro and In Vivo Evaluations of Berberine-Loaded Microparticles Filled In-House 3D Printed Hollow Capsular Device for Improved Oral Bioavailability

The low oral bioavailability, short biological half-life, high dose, and frequent dosing of berberine (BBR) contribute to its restricted clinical use despite its extensive pharmacological activity. Thus, the objective of this study was to formulate sustained-release microparticles (MPs) using a pH-independent release polymer and to evaluate their potential to improve the oral bioavailability of BBR. BBR loaded MPs were prepared using the emulsion crosslinking method and evaluated for particle size, circularity, morphology, entrapment efficiency, solid-state analysis, swelling index, and in vitro BBR release study fitted with different models of release kinetics. The MPs exhibited desired particle sizes ranges between 11.09-11.62 μm and were almost spherical in shape, as confirmed by the circularity value and micrographic images. A loss of BBR crystallinity was observed after encapsulation in MPs, as evident from various solid-state analyses. The final optimized batch (F3) showed highest % BBR entrapment efficiency value of 81.63% ± 4.9. The in vitro BBR release performance in both acidic and alkaline media showed the desired sustained release behavior from the crosslinked MPs, where the maximum BBR release was observed at alkaline pH, which is in accordance with the swelling study data. In the in vivo study, the oral absorption profiles of BBR from both pristine and MPs formats were investigated using in-house prototyped 3D printed hollow capsules as a unit dose carrier. In vivo data showed sustained and prolonged absorption behavior of BBR from MPs compared to their pristine counterparts, which resulted in a cumulative increment of relative oral bioavailability to mitigate the aforementioned issues related to BBR. Graphical Abstract.

Enteric and hydrophilic polymers enhance dissolution and absorption of poorly soluble acidic drugs based on micro-environmental pH-modifying solid dispersion

The oral bioavailability of poorly water-soluble active pharmaceutical ingredient (API) is often inadequate for the desired therapeutic effect. Micro-environmental pH-modifying solid dispersion (micro pHm SD) is an effective method for enhancing the dissolution of pH-dependent soluble APIs. However, erratic bioavailability of these drugs was often found when the micro pHm SD of the drugs was orally administrated and passed through the gastrointestinal tract. Because the added alkalizer in micro pHm SD could be neutralized by the acid in the stomach, as a result not enough alkalizer is left to form alkaline micro-environment around the drug in the intestine, leading to poor dissolution and bioavailability of API. Enteric polymers are applicable materials for site-specific drug delivery that are insoluble in gastric tract but soluble in the intestine targeted for drug release. In this study, a poorly water-soluble model drug, toltrazuril (TOL), was prepared as enteric micro pHm SD with enteric, hydrophilic polymers and alkalizer. The surface of enteric micro pHm SD tablets staining and alkalizer protection test in the acid dissolution medium qualitatively and quantitatively confirmed the protective effects of the enteric polymer on the alkalizer. Dissolution studies revealed that the drug release from the enteric micro pHm SDs was improved significantly compared with micro pHm SD with no enteric polymer. The pH-dependent solubility of enteric polymer had effects on the dissolution of APIs from the SDs in neutral medium. Enteric micro pHm SDs with higher proportion of enteric polymer showed higher C_max and dissolution rate of TOL. The physicochemical characterization and the molecular interaction between drug and matrix were analyzed by electron microscopy (SEM), differential scanning calorimetry (DSC), and fourier transform infrared spectroscopy (FTIR), finding that the formation of hydrogen bonds between TOL and matrix was helpful to promote dissolution of TOL. Ca(OH)₂-TOL-PVPk30-HPMCAS 8: 8: 18: 6 was determined as the most optimal enteric micro pHm SD, which significantly improved the bioavailability of TOL and its active metabolism (TOLSO, TOLSO₂) in pharmacokinetic study and could effectively reduce the irritation of the gastrointestinal mucosa caused by the alkalizer Ca(OH)₂ when the SD was orally administrated to rabbits. The present study demonstrates that formulating APIs with poor water solubility as enteric micro pHm SD is an effective method for protecting the alkalizer in SD and improving the dissolution of APIs and the bioavailability following oral administration.

Micelles entrapped microparticles technology: a novel approach to resolve dissolution and bioavailability problems of poorly water soluble drugs

Aim: Aim of this study was to design a solid oral delivery system for a weakly basic drug such as dasatinib (DAS), so as to achieve pH-independent dissolution and improved oral bioavailability.Methods: DAS was solubilised using sodium lauryl sulphate as an aqueous micellar system and such a system containing lactose monohydrate as carrier was spray-dried to obtain a solid mass. Subsequently, the DAS-solid was converted into a tablet using conventional tableting methods.Results: The dissolution study revealed pH-independent dissolution over a wide range of pH conditions. An in vivo bioavailability testing on rats revealed an improved C_max and AUC_0-24. Similarly, viability assay showed a better inhibitory effect of spray-dried dasatinib over the DAS.Conclusions: Micellar solubilisation and spray-drying technology can be approached to resolve poor dissolution and bioavailability of drugs belonging to biopharmaceutical classification system II and III. This technology is amenable to scale-up and has commercial potential.

Formulation of Cinnarizine for Stabilization of Its Physiologically Generated Supersaturation

Physiologically generated supersaturation and subsequent crystallization of a weakly basic drug in the small intestine leads to compromised bioavailability. In this study, the pH-induced crystallization of cinnarizine (CNZ) in the presence of different polymers was investigated. Inhibitory effect of Eudragit L100 (Eu) on crystallization of CNZ at varying supersaturation ratios was examined. The effect of Eu on the dissolution behavior of CNZ from CNZ/Eu physical mixtures (PMs) and solid dispersions (SDs) was assessed. Results showed that both Eu and hydroxypropyl methylcellulose (HPMC) have a considerable maintenance effect on supersaturation of CNZ but Eu was more effective than HPMC. When Eudragit was used the phenomenon of liquid-liquid phase separation (formation of colloidal phase) was observed at supersaturation ratio of 20 times above the solubility of the drug. PMs showed a higher area under the dissolution curve (AUDC) compared with plain CNZ. In contrast, SDs showed a lower AUDC than plain CNZ. For SDs, the AUDC was limited by the slow release of the drug from Eu in acidic pH which in turn hindered the creation of CNZ supersaturation following the transition of acidic to neutral pH. From these findings, it can be concluded that the ability of the formulation to generate supersaturation state and also maintain the supersaturation is vital for improving the dissolution of CNZ.

Stabilization benefits of single and multi-layer self-nanoemulsifying pellets: A poorly-water soluble model drug with hydrolytic susceptibility

Solidified self-nanoemulsifying drug delivery systems (SNEDDS) offer strong option to enhance both drug aqueous solubility and stability. The current study was designed to evaluate the potential stabilization benefits of solidifying cinnarizine (CN) liquid SNEDDS into single and multi-layer self-nanoemulsifying pellets (SL-SNEP and ML-SNEP, respectively). The selected formulations were enrolled into accelerated, intermediate and long-term stability studies. The chemical stability was assessed based on the % of intact CN remaining in formulation. The physical stability was assessed by monitoring the in-vitro dissolution and physical appearance of the formulations. The degradation pathway of CN within lipid-based formulation was proposed to involve a hydroxylation reaction of CN molecule. The chemical stability study revealed significant CN degradation in liquid SNEDDS, SL-SNEP and ML-SNEP (lacking moisture-sealing) within all the storage conditions. In contrast, the moisture sealed ML-SNEP showed significant enhancement of CN chemical stability within the formulation. In particular, ML-SNEP coated with Kollicoat Smartseal 30D showed superior CN stabilization and no significant decrease in dissolution efficiency, at all the storage conditions. The observed stability enhancement is owing to the complete isolation between CN and SNEDDS layer as well as the effective moisture protection provided by Kollicoat Smartseal 30D. Hence, the degradation problem could be eradicated completely. The incorporation of silicon dioxide had an important role in the inhibition of pellet agglomeration upon storage. Accordingly, ML-SNEP coated with Kollicoat Smartseal 30D and/or silicon dioxide could be an excellent dosage form that combine dual enhancement of CN solubilization and stabilization.

Improved Dissolution of Dipyridamole with the Combination of pH-Modifier and Solid Dispersion Technology

The aim of this study was to develop a pH-independent release formulation of dipyridamole (DP) by the combined use of pH-modifier technology and solid dispersion (SD) technology employing enteric polymer, Eudragit^® S100 (Eud). Tartaric acid (TA) was selected as an appropriate pH-modifier in terms of improving the dissolution behavior of DP under neutral conditions. Upon optimization of the ratio of TA to DP, SD of DP with Eud and TA (SD-Eud/DP/TA) was prepared by a freeze-drying method. Scanning electron microscopic images revealed that DP was dispersed in the polymer in SD-Eud/DP/TA, and DP in SD-Eud/DP/TA was in an amorphous state, supported by powder X-ray diffraction and differential scanning calorimetry analyses. The dissolution behavior of SD-Eud/DP/TA was not dependent on the pH of the medium, although SD-Eud/DP exhibited very limited dissolution behavior under neutral conditions. Spectroscopic analysis suggested that there might be inter-molecular interaction among DP, TA and enteric polymer in SD-Eud/DP/TA, possibly leading to the stable pH-independent dissolution behavior of SD-Eud/DP/TA. TA in SD-Eud/DP/TA promoted the degradation of DP, suggesting that improving the stability of DP in SD-Eud/DP/TA might be key for its practical use. From these results, pH-independent dissolution behavior of SD-Eud/DP/TA could be achieved by an enteric polymer-based solid dispersion with a pH-modifier.

Preparation of Porous Polysaccharides Templated by Coordination Polymer with Three-Dimensional Nanochannels

Polymerization of monosaccharide monomers usually suffers from the production of polysaccharides with ill-defined structures because of the uncontrolled random reactions among many reactive hydroxyl groups on saccharide monomers. In particular, rational synthesis of polysaccharides with porosity approximating molecular dimensions is still in its infancy, despite their usefulness as drug carriers. Here, we disclose an efficient synthetic methodology for the preparation of polysaccharides with controllable mesoporosity in the structure, utilizing [Cu₃(benzene-1,3,5-tricarboxylate)]_n (HKUST-1; 1) as templates. Cationic ring-opening polymerization of 1,6-anhydro glucose was performed in nanochannels of 1, followed by removal of the host frameworks, giving polysaccharide particles as replicas of the original molds. Nitrogen adsorption measurement revealed that the obtained polysaccharide particles contained high mesoporosity in the structure, which could be controlled systematically depending on the polymerization conditions. Because of the large specific surface area, tunable porosity and particle size, we could also demonstrate the capabilities of our polysaccharides for loading and releasing of a drug molecule and protein.

Preparation and tableting of long-term stable amorphous rutin using porous silica

Amorphous state of drugs increases the oral bioavailability, but typically faces physical stability problems. Amorphous rutin was generated and physically stabilized by encapsulating inside mesopores of porous AEROPERL® 300 Pharma and named as rutin CapsMorph® in this study. AEROPERL® 300 Pharma was loaded with rutin dissolved in DMSO containing Tween 80, and subsequently the solvent evaporated (wetness impregnation method). The loading process was monitored by light microscopy and scanning electron microscopy (SEM). X-ray diffraction (XRD) and differential scanning calorimetry (DSC) were used to confirm the amorphous state in AEROPERL® 300 Pharma. A loading of 20% of the rutin-AEROPERL® 300 Pharma mixture was obtained. The amorphous state proved to be stable over 2years of storage at room temperature. Due to the amorphous state and the nanosize of the rutin in the mesopores, the kinetic saturation solubility increased to about 4mg/ml (water, 0.1MHCl, pH 6.8PBS) compared to the maximum observed thermodynamic equilibrium solubility of rutin raw drug powder of only 74.48±1.42μg/ml in pH 6.8PBS (=increase by factor about 54). The dissolution velocity also increased distinctly, e.g. about 96.1% of rutin dissolution from CapsMorph® powder in water within 5min compared to less than 40% of raw drug powder after 3h. Tablets were produced with rutin CapsMorph®, raw drug powder and their dissolution velocity compared to a marketed product. About 83.0-95.6% were released from the rutin CapsMorph® tablet within 5min, compared to 42.7-52.5% from the marketed tablet after 3h (water, 0.1MHCl, pH 6.8PBS). After dissolution the supersaturation level of rutin CapsMorph® remained over about 2h, then solubility slowly reduced, but remained after 48h still multifold above the thermodynamic rutin solubility. This should be sufficient for many poorly soluble drugs to achieve a sufficient bioavailability. For optimal exploitation of the supersaturation, a multiple step release system could be used, e.g. release of CapsMorph® particles every 2-3h.

Instrumentation of Flow-Through USP IV Dissolution Apparatus to Assess Poorly Soluble Basic Drug Products: a Technical Note

Supersaturation and precipitation are common limitations encountered especially with poorly soluble basic drugs. The aims of this work were to explore the pattern of dissolution and precipitation of poorly soluble basic drugs using a United States Pharmacopoeia (USP) IV dissolution apparatus and to compare it to the widely used USP II dissolution apparatus. In order to investigate the influence of gastric emptying time on bioavailability, tables of two model drugs (dipyridamole 100 mg and cinnarizine 15 mg) were investigated and pH change from 1.2 to 6.8 were achieved after 10, 20 or 30 min using USP II or USP IV dissolution apparatuses. Using USP II, dipyridamole and cinnarizine concentrations dropped instantly as a result of drug precipitation with drug crystals evident in the dissolution vessel. At pH change times of 10, 20 and 30 min, the total amount of dissolved drug was dependent on pH change time. Using USP IV, at a flow rate of 8 ml/min, it was possible to have comparable release to agitation at 50 rpm using USP II suggesting that comparable hydrodynamic forces are possible. No drop in drug percentage occurs as the dissolved fraction was readily emptied from the flow cell, preventing drug accumulation in the dissolution medium. However, a negligible percentage of drug release took place following pH change. In conclusion, the use of the flow-through cell dissolution provided laminar flow, use of realistic fluid volumes and avoided precipitation of dissolved drug fraction in the gastric phase as it is discharged before pH change.

Development of intramammary delivery systems containing lasalocid for the treatment of bovine mastitis: impact of solubility improvement on safety, efficacy, and milk distribution in dairy cattle

Background

Mastitis is a major disease of dairy cattle. Given the recent emergence of methicillin-resistant Staphylococcus aureus as a cause of bovine mastitis, new intramammary (IMA) treatments are urgently required. Lasalocid, a member of the polyether ionophore class of antimicrobial agents, has not been previously administered to cows by the IMA route and has favorable characteristics for development as a mastitis treatment. This study aimed to develop an IMA drug delivery system (IMDS) of lasalocid for the treatment of bovine mastitis.

Methods

Minimum inhibitory concentrations (MICs) were determined applying the procedures recommended by the Clinical and Laboratory Standards Institute. Solid dispersions (SDs) of lasalocid were prepared and characterized using differential scanning calorimetry and Fourier transform infrared spectroscopy. IMDSs containing lasalocid of micronized, nano-sized, or as SD form were tested for their IMA safety in cows. Therapeutic efficacy of lasalocid IMDSs was tested in a bovine model involving experimental IMA challenge with the mastitis pathogen Streptococcus uberis.

Results

Lasalocid demonstrated antimicrobial activity against the major Gram-positive mastitis pathogens including S. aureus (MIC range 0.5–8 μg/mL). The solubility test confirmed limited, ion-strength-dependent water solubility of lasalocid. A kinetic solubility study showed that SDs effectively enhanced water solubility of lasalocid (21–35-fold). Polyvinylpyrrolidone (PVP)-lasalocid SD caused minimum mammary irritation in treated cows and exhibited faster distribution in milk than either nano or microsized lasalocid. IMDSs with PVP-lasalocid SD provided effective treatment with a higher mastitis clinical and microbiological cure rate (66.7%) compared to cloxacillin (62.5%).

Conclusion

Lasalocid SD IMDS provided high cure rates and effectiveness in treating bovine mastitis with acceptable safety in treated cows.

Recent advances in delivery systems and therapeutics of cinnarizine: a poorly water soluble drug with absorption window in stomach

Low solubility causing low dissolution in gastrointestinal tract is the major problem for drugs meant for systemic action after oral administration, like cinnarizine. Pharmaceutical products of cinnarizine are commercialized globally as immediate release preparations presenting low absorption with low and erratic bioavailability. Approaches to enhance bioavailability are widely cited in the literature. An attempt has been made to review the bioavailability complications and clinical therapeutics of poorly water soluble drug: cinnarizine. The interest of writing this paper is to summarize the pharmacokinetic limitations of drug with special focus on strategies to improvise bioavailability along with effectiveness of novel dosage forms to circumvent the obstacle. The paper provides insight to the approaches to overcome low and erratic bioavailability of cinnarizine by cyclodextrin complexes and novel dosage forms: self-nanoemulsifying systems and buoyant microparticulates. Nanoformulations need to systematically explored in future, for their new clinical role in prophylaxis of migraine attacks in children. Clinical reports have affirmed the role of cinnarizine in migraine prophylaxis. Research needs to be dedicated to develop dosage forms for efficacious bioavailability and drug directly to brain.

Floating lipid beads for the improvement of bioavailability of poorly soluble basic drugs: in-vitro optimization and in-vivo performance in humans

The challenge in developing oral drug delivery systems of poorly soluble basic drugs is primarily due to their pH dependent solubility. Cinnarizine (CNZ), a model for a poorly soluble basic drug, has pH dependent solubility; where it dissolves readily at low pH in the stomach and exhibits a very low solubility at pH values greater than 4. It is also characterized by a short half life of 3-6h, which requires frequent daily administration resulting in poor patient compliance. In an attempt to solve these problems, extended release floating lipid beads were formulated. A 2(4) full factorial design was utilized for optimization of the effects of various independent variables; lipid:drug ratio, % Pluronic F-127, % Sterotex, and Gelucire 43/01:Gelucire 50/13 ratio, on the loading efficiency and release of CNZ from the lipid beads. In-vivo pharmacokinetic study of the optimized CNZ-lipid beads compared to Stugeron® (reference standard) was performed in healthy human volunteers. A promising approach for enhancing the bioavailability of the poorly soluble basic drug, CNZ, utilizing novel and simple floating lipid beads was successfully developed. Zero order release profile of CNZ was achieved for 12h. Mean AUC0-24 and AUC0-∞ of the optimized CNZ-loaded lipid beads were 4.23 and 6.04 times that of Stugeron® tablets respectively.

Chitosan-xanthan gum microparticle-based oral tablet for colon-targeted and sustained delivery of quercetin

CONTEXT

Quercetin (QUE) is a flavonoid with antioxidant/anti-inflammatory properties, poorly absorbed when orally administered.

OBJECTIVES

To prepare chitosan/xanthan gum microparticles to increase QUE oral bioavailability and optimize its release in the colon.

MATERIALS AND METHODS

Chitosan/xanthan gum hydrogel embedding QUE was spray-dried to obtain microparticles characterized by size, scanning electron microscopy, differential scanning calorimetry and X-ray diffraction. Microparticles were compressed into tablets, coated with Eudragit® to further prevent degradation in acidic pH. The swelling degree and QUE release in simulated gastric and intestinal pH were investigated.

RESULTS

Microparticles were smooth and spherical, around 5 µm, with successful QUE loading. Microparticle tablets provided resistance to acidic conditions, allowing complete drug release in alkaline pH, mimicking colonic environment. The release was controlled by non-Fickian diffusion of the dissolved drug out of the swollen polymeric tablet.

DISCUSSION AND CONCLUSION

Microparticle tablets represent a promising dosage form for QUE delivery to the colon in the oral therapy of inflammatory-based disorders.

Encapsulation and Delivery of Crystalline Hydrophobic Nutraceuticals using Nanoemulsions: Factors Affecting Polymethoxyflavone Solubility

Polymethoxyflavones (PMF) isolated from citrus peel have potent anti-cancer activity, however their utilization as functional ingredients in foods is currently limited because of their high melting point and poor water-solubility. The influence of oil type and concentration, hydrophilic polymer addition, and simulated intestinal conditions on PMF (5-hydroxytangeretin) solubility in solutions and nanoemulsions was examined. The saturation concentration of PMF in water was relatively low (0.93 µM), but could be increased appreciably by adding certain hydrophilic polymers: polyethylene glycol (PEG) and β-cyclodextrin (CD) were ineffective at increasing solubility, but poly(vinyl alcohol) (PVA) and hydroxypropyl methylcellulose (HPMC) greatly enhanced solubility (e.g., > 6 µM for 0.5 % polymer). PMF was more soluble in medium chain triglycerides (MCT, 6.1 mM) than long chain triglycerides (LCT, 4.2 mM). The encapsulation efficiency of PMF in oil-in-water nanoemulsions was higher when MCT was used as the oil phase rather than LCT, and could be increased by increasing the oil droplet content. The solubility of PMF in simulated small intestinal fluids was increased by solubilization in bile micelles and mixed micelles formed during lipid digestion. These results have important implications for the development of functional foods fortified with bioactive hydrophobic components aimed at improving human health and wellness.

Mesoporous systems for poorly soluble drugs

Utilization of inorganic mesoporous materials in formulations of poorly water-soluble drugs to enhance their dissolution and permeation behavior is a rapidly growing area in pharmaceutical materials research. The benefits of mesoporous materials in drug delivery applications stem from their large surface area and pore volume. These properties enable the materials to accommodate large amounts of payload molecules, protect them from premature degradation, and promote controlled and fast release. As carriers with various morphologies and chemical surface properties can be produced, these materials may even promote adsorption from the gastrointestinal tract to the systemic circulation. The main concern regarding their clinical applications is still the safety aspect even though most of them have been reported to be safely excreted, and a rather extensive toxicity screening has already been conducted with the most frequently studied mesoporous materials. In addition, the production of the materials on a large scale and at a reasonable cost may be a challenge when considering the utilization of the materials in industrial processes. However, if mesoporous materials could be employed in the industrial crystallization processes to produce hybrid materials with poorly soluble compounds, and hence to enhance their oral bioavailability, this might open new avenues for the pharmaceutical industry to employ nanotechnology in their processes.