Improved dissolution and pharmacokinetic behavior of cyclosporine A using high-energy amorphous solid dispersion approach

Combination of PEGylation and Cationization on Phospholipid-Coated Cyclosporine Nanosuspensions for Enhanced Ocular Drug Delivery

Strong precorneal clearance mechanisms including reflex blink, constant tear drainage, and rapid mucus turnover constitute great challenges for eye drops for effective drug delivery to the ocular epithelium. In this study, cyclosporine A (CsA) for the treatment of dry eye disease (DED) was selected as the model drug. Two strategies, PEGylation for mucus penetration and cationization for potent cellular uptake, were combined to construct a novel CsA nanosuspension (NS@lipid-PEG/CKC) by coating nanoscale drug particles with a mixture of lipids, DSPE-PEG2000, and a cationic surfactant, cetalkonium chloride (CKC). NS@lipid-PEG/CKC with the mean size ∼173 nm and positive zeta potential ∼+40 mV showed promoted mucus penetration, good cytocompatibility, more cellular uptake, and prolonged precorneal retention without obvious ocular irritation. More importantly, NS@lipid-PEG/CKC recovered tear production and goblet cell density more efficiently than the commercial cationic nanoemulsion on a dry eye disease rat model. All results indicated that a combination of PEGylation and cationization might provide a promising strategy to coordinate mucus penetration and cellular uptake for enhanced drug delivery to the ocular epithelium for nanomedicine-based eye drops.

Fabrication and evaluation of stable amorphous polymer-drug composite particles via a nozzle-free ultrasonic nebulizer

We present a promising method for producing amorphous drug particles using a nozzle-free ultrasonic nebulizer with polymers, specifically polyvinylpyrrolidone (PVP), poly(acrylic acid) (PAA), and Eudragit® S 100 (EUD). Model crystalline phase drugs-Empagliflozin, Furosemide, and Ilaprazole-are selected. This technique efficiently produces spherical polymer-drug composite particles and demonstrates enhanced stability against humidity and thermal conditions, compared to the drug-only amorphous particles. The composite particles exhibit improved water dissolution compared to the original crystalline drugs, indicating potential bioavailability enhancements. While there are challenges, including the need for continuous water supply for ultrasonic component cooling, dependency on the solubility of polymers and drugs in volatile organic solvents, and mildly elevated temperatures for solvent evaporation, our method offers significant advantages over traditional approaches. It provides a straightforward, flexible process adaptable to various drug-polymer combinations and consistently yields spherical amorphous solid dispersion (ASD) particles with a narrow size distribution. These attributes make our method a valuable advancement in pharmaceutical drug formulation and delivery.

Encapsulation of Cyclosporine A-Loaded PLGA Nanospheres in Alginate Microbeads for Anti-Inflammatory Application

The controlled release of cyclosporine A (CsA) microencapsulated in alginate microbeads is a novel drug delivery system for the treatment of inflammatory diseases. In this study, CsA-loaded nanospheres encapsulated in alginate microbeads were applied to evaluate their controlled release profile and anti-inflammatory activity. Initially, a controlled-release drug delivery system was created by encapsulating CsA-loaded PLGA nanospheres within alginate microbeads. CsA-loaded PLGA nanospheres had a diameter of 418.70 ± 59.08 nm, a zeta potential of -22 ± 0.57 mV, and a polydispersity index of 0.517 ± 0.010. CsA-loaded nanosphere-encapsulated alginate microbeads were stable for 37 days. After encapsulating CsA-loaded PLGA nanospheres in the alginate microbeads, 5.60% of CsA was released after 24 h, and approximately 85.90% of the drugs were diffused until day 64. The cytotoxic and anti-inflammatory properties of the CsA released from the microbeads were evaluated in vitro using a murine macrophage cell line (RAW 264.7 cells). CsA-loaded nanosphere-encapsulated alginate microbeads inhibited 39.47 ± 1.71% of nitric oxide production from the RAW 264.7 cells on day 3, whereas nanosphere-encapsulated alginate microbeads inhibited 18.45 ± 1.56% only. CsA released from CsA-loaded nanosphere-encapsulated alginate microbeads had a RAW cell viability of 82.73 ± 5.58% on day 3 compared to 87.59 ± 0.69% of nanosphere-encapsulated alginate microbeads. The efficacy of the CsA-loaded nanosphere-encapsulated alginate microbeads in protecting the immune system via a controlled drug delivery system was established through anti-inflammatory and cell viability evaluation. Based on this research, the controlled release of CsA-loaded nanosphere-encapsulated alginate microbeads provides an innovative treatment for inflammatory diseases.

Rapidly Dissolving Trans-scleral Microneedles for Intraocular Delivery of Cyclosporine A

Cyclosporine A (CsA) is a cyclic peptide immunosuppressant drug that is beneficial in the treatment of various ocular diseases. However, its ocular bioavailability in the posterior eye is limited due to its poor aqueous solubility. Conventional CsA formulations such as a solution or emulsion permeate poorly across the eye due to various static and dynamic barriers of the eye. Dissolvable microneedle (MN)-based patches can be used to overcome barrier properties and, thus, enhance the ocular bioavailability of CsA in the posterior eye. CsA-loaded dissolvable MN patches were fabricated using polyvinylpyrrolidone (PVP) and characterized for MN uniformity and sharpness using SEM. Further characterization for its failure force, penetration force, and depth of penetration were analyzed using a texture analyzer. Finally, the dissolution time, ex vivo permeation, and ocular distribution of cyclosporine were determined in isolated porcine eyes. PVP MNs were sharp, uniform with good mechanical properties, and dissolved within 5 min. Ocular distribution of CsA in a whole porcine eye perfusion model showed a significant increase of CsA levels in various posterior segment ocular tissues as compared to a topically applied ophthalmic emulsion (Restasis®) (P < 0.001). Dissolving MNs of CsA were prepared, and the MN arrays can deliver CsA to the back of the eye offering potential for treating various inflammatory diseases.

Moisture Sorption by Polymeric Excipients Commonly Used in Amorphous Solid Dispersions and its Effect on Glass Transition Temperature: II. Cellulosic Polymers

Moisture sorption by polymeric carriers used for the development of amorphous solid dispersions (ASDs) plays a critical role in the physical stability of dispersed drugs since moisture may decrease glass transition temperature (T_g) and thereby increase molecular mobility of drugs leading to their crystallization. To assist the selection of appropriate polymers for ASDs, we conducted moisture sorption by five types of cellulosic polymers, namely, hydroxypropyl cellulose (HPC), hydroxypropyl methyl cellulose (HPMC), hydroxypropyl methyl cellulose acetate succinate (HPMCAS), hydroxypropyl methyl cellulose phthalate (HPMCP), and ethyl cellulose (EC), as functions of relative humidity (10 to 90% RH) and temperature (25 and 40 °C). The moisture sorption was in the order of HPC>HPMC>HPMCP>HPMCAS>EC, and there was no significant effect of the molecular weights of polymers on moisture uptake. There was also less moisture sorption at 40 °C than that at 25 °C. Glass transition temperatures (T_g) of the polymers decreased with the increase in moisture content. However, the plasticizing effect by moisture on HPC could not be determined fully since, despite being amorphous, there were very little baseline shifts in DSC scans. There was also very shallow baseline shift for HPMC at >1% moisture content. In contrast, T_g of HPMCAS and HPMCP decreased in general agreement with the Gordon-Taylor/Kelley-Bueche equation, and EC was semicrystalline having both T_g and melting endotherm, with only minor effect of moisture on T_g. The results of the present investigation would lead to a systematic selection of polymeric carriers for ASDs.

Preparation and pharmacokinetics in vivo of linarin solid dispersion and liposome

Objective

The current investigation aimed to determine the appropriate dosage form by comparing solid dispersion and liposome to achieve the purpose of improving the solubility and bioavailability of linarin.

Methods

Linarin solid dispersion (LSD) and linarin liposome (LL) were developed via the solvent method and the thin film hydration method respectively. The Transwell chamber model of Caco-2 cells was established to evaluate the absorption of drug. The pharmacokinetics of linarin, LSD and LL in rats after ig administration were carried out by high performance liquid chromatography (HPLC) method.

Results

The solubility of LSD and LL was severally 3.29 times and 3.09 times than that of linarin. The permeation coefficients of LSD and LL were greater than 10⁻⁶, indicating that the absorption of LSD and LL were both better than linarin. The bioavailability of the LSD was 3.363 times higher than that of linarin, and the bioavailability of LL was 0.9886 times higher than that of linarin.

Conclusion

The linarin was more suitable for making solid dispersion to enhance its solubility and bioavailability.

Nanocrystal solid dispersion of fuzapladib free acid with improved oral bioavailability

This study aimed to develop an oral nanocrystal solid dispersion (nCSD) of fuzapladib (FZP) with enhanced absorbability for the treatment of acute pancreatitis (AP). The hydration properties of crystalline FZP free acid (crystalline FZP) and FZP sodium salt (FZP/Na) were assessed to select a stable crystal form. The nCSD of FZP free acid (nCSD/FZP) was prepared using a multi-inlet vortex mixer and evaluated in terms of physicochemical and pharmacokinetic properties. The results of X-ray powder diffraction analysis indicated that crystalline FZP was stable as an anhydrate, while FZP/Na was converted to its monohydrate at water activity of above 0.2. The nanocrystals in nCSD/FZP were dispersed in hydroxy propyl cellulose-SSL, and their mean particle size were 160 nm with uniform spherical shape. In dissolution testing, nCSD/FZP exhibited rapid dissolution compared with crystalline FZP and reached a saturated concentration of FZP within initial 30 min. After oral administration (2 mg-FZP/kg) to rats, the maximum plasma concentration and bioavailability were 7.3- and 5.2-fold higher for nCSD/FZP than crystalline FZP, respectively, due to improved dissolution by nanosization. In conclusion, nCSD/FZP may be a novel oral dosage form with enhanced absorbability facilitating potent therapeutic effects of FZP for the treatment of AP in animals.

Solid Dispersion Formulations by FDM 3D Printing-A Review

Additive manufacturing (AM) is revolutionizing the way medicines are designed, manufactured, and utilized. Perhaps, AM appears to be ideal for the fit-for-purpose manufacturing of medicines in contrast to the several disadvantages associated with the conventional fit-for-all mass production that accounts for less than 50% of pharmacotherapeutic treatment/management of diseases especially among children and elderly patients, as well as patients with special needs. In this review, we discuss the current trends in the application of additive manufacturing to prepare personalized dosage forms on-demand focusing the attention on the relevance of coupling solid dispersion with FDM 3D printing. Combining the two technologies could offer many advantages such as to improve the solubility, dissolution, and oral bioavailability of poorly soluble drugs in tandem with the concept of precision medicine and personalized dosing and to address the dilemma of commercial availability of FDM filaments loaded with Class II and/or Class IV drugs. However, thermal treatment especially for heat-sensitive drugs, regulatory, and ethical obligations in terms of quality control and quality assurance remain points of concern. Hence, a concerted effort is needed between the scientific community, the pharmaceutical industries, the regulatory agencies, the clinicians and clinical pharmacists, and the end-users to address these concerns.

Role of Surfactants on Release Performance of Amorphous Solid Dispersions of Ritonavir and Copovidone

PURPOSE

To understand the role of different surfactants, incorporated into amorphous solid dispersions (ASDs) of ritonavir and copovidone, in terms of their impact on release, phase behavior and stabilization of amorphous precipitates formed following drug release.

METHODS

Ternary ASDs with ritonavir, copovidone and surfactants (30:70:5 w/w/w) were prepared by rotary evaporation. ASD release performance was tested using Wood's intrinsic dissolution rate apparatus and compared to the binary drug-polymer ASD with 30% drug loading. Size measurement of amorphous droplets was performed using dynamic light scattering. Solid state characterization was performed using attenuated total reflectance-infrared spectroscopy, differential scanning calorimetry and scanning electron microscopy.

RESULTS

All surfactant-containing ASDs showed improvement over the binary ASD. Span 85 and D-α-tocopheryl polyethylene glycol succinate (TPGS) showed complete release with no evidence of AAPS or crystallization whereas Span 20 and Tween 80 showed < 50% release with amorphous amorphous phase separation (AAPS). Span 20 also induced solution crystallization. Sodium dodecyl sulfate (SDS) showed very rapid, albeit incomplete (~ 80%) release. AAPS was not observed with SDS. However, crystallization on the dissolving solid surface was noted. Span 20 and TPGS formed the smallest and most size-stable droplets with ~ 1 µm size whereas coalescence was noted with other surfactants.

CONCLUSIONS

Surfactants improved the release performance relative to the binary ASD. Different surfactant types impacted overall performance to varying extents and affected different attributes. Overall, Span 85 showed best performance (complete release, no crystallization/AAPS and small droplet size). Correlation between physicochemical properties and surfactant performance was not observed.

A new nanosuspension prepared with wet milling method for oral delivery of highly variable drug Cyclosporine A: Development, optimization and in vivo evaluation

Cyclosporine A (CsA) is a cyclic polypeptide, that has been widely used for immunosuppression. This study aims to develop nanosuspension for oral administration of CsA using the wet milling (WM) method one of the top-down technologies. The WM method was optimized by studying the effects of critical process parameters for WM on the particle size (PS), particle size distribution (PDI), and zeta potential (ZP) of nanosuspensions using the Design of Experiment (DoE) approach. Nanosuspension was developed using hydroxypropyl methylcellulose (HPMC) and sodium dodecyl sulfate (SDS) and in vitro characterization studies were performed. In vitro dissolution and in vivo pharmacokinetic studies were conducted with biorelevant media (fasted and fed state simulated fluids) and fasted and fed states in rats, respectively. In vivo immunological studies were also performed. PS, PDI, and ZP values for nanosuspension were approximately 600 nm, 0.4, -25 mV, respectively. The solubility of CsA was increased by 4.5-folds by nanosuspensions. Dissolution studies showed that nanosuspension had higher dissolution than the commercial product in the FeSSIF medium. The pharmacokinetic study indicated that AUC_0-24 values of CsA nanosuspension were to be 2.09 and 5.51-fold higher than coarse powder in fasted and fed conditions, respectively. Immunological studies were carried out after oral administration of nanosuspension for 21 days, the ratio of CD4+/CD8+ was found to be more acceptable than the commercial product. These results demonstrated that nanosuspension is a promising approach for increasing the bioavailability and avoiding the food effect on absorption of CsA which one of the highly variable drugs.

Impact of chirality on the amorphous state of conglomerate forming systems: a case study of N-acetyl-α-methylbenzylamine

The present work aims at addressing the issue of molecular handedness in glassy and liquid states and its impact on heterogeneous equilibrium. For this purpose, we evaluated the glass forming ability (GFA), crystallization propensity, molecular mobility and hydrogen bonding structure of a chiral conglomerate forming system, N-acetyl-α-methylbenzylamine (Nac-MBA), at various enantiomeric excesses (ees) using experimental and computational techniques. We revealed that the rich relaxational landscape (Debye (D), α, β_JG and ϒ) and the temperature dependence of the time scale of each process were insensitive to chirality. The most remarkable impact of chirality was expressed on the GFA and the recrystallization of heterochiral arrangements. In fact the GFA increases with decreasing ee, while the crystallization propensity increases with increasing ee. The counter enantiomer acted as a disruptor of crystallization and favored the glass formation upon cooling. The molecular dynamics simulation (MDS) results on the architecture of chiral sequences showed that homochiral sequences were more favorable when compared to heterochiral ones in the liquid state. However, this predisposition to form homochiral sequences in the liquid state was not the precursor of the future crystalline structure, since the liquid or the glassy system recrystallizes as heterochiral sequences. As per our understanding the crystallization was mostly controlled by the mean free migration path of an enantiomer to build homochiral or heterochiral sequences. In the present case, it seems that the mean free migration path achieved by an enantiomer for heterochiral sequences is shorter compared to homochiral arrangements in such a way that the crystallization of the metastable racemic compound is kinetically more favorable.

Amorphous solid dispersions of cyclosporine A with improved bioavailability prepared via hot melt extrusion: Formulation, physicochemical characterization, and in vivo evaluation

In this study, the amorphous solid dispersions of cyclosporine A (CsA-ASDs) were prepared by hot melt extrusion (HME) with PVP K12 as carrier to improve the oral bioavailability of CsA. The polymers were screened by solubilization and recrystallization inhibition experiments, then the CsA-ASDs were prepared with optimized technological parameters and characterized on thermodynamics and morphology. The results showed that CsA was dispersed among PVP K12 as amorphous form in CsA-ASDs, and the infrared spectrum testified that there was possible hydrogen bond interaction between CsA and PVP K12. The in vivo pharmacokinetics of CsA formulations in rats were analyzed via LC-MS. The AUC of CsA-ASD tablets increased by 7.3 times compared to CsA bulk powder and 3.1 times in contrast to CsA-PM tablets, respectively. The experiment proved that CsA-ASD tablets significantly improved the dissolution and absorption of the drug. This study had a reference value for the bioavailability improvement of oral CsA preparations.

Synthesis and characterization of osmotic pump capsules containing polyoxyethylene and pH modifier to control the release of nifedipine

The aim of this study was to formulate osmotic pump capsules (OPCs) to control the release of nifedipine (NP). NP solid dispersion was prepared by solvent evaporation method. The prepared mixture of NP solid dispersion and various excipients were filled into the commercial HPMC hard capsule shells and then coated with cellulose acetate (CA) solution to form NP-OPC. The CA coating solution consisted of CA as semi-permeable membrane, and Poloxamer 188 as pore formers. The impact of addition agents, citric acid and pore formers on in vitro drug release were investigated. Furthermore, the study has highlighted the impact of paddle speed and the pH value of release media, on the release and compared the release with the commercial controlled release tablets. The in vitro drug release study indicated that drug release could reach 95% in 24 h with optimal formulation, and interestingly model fitting showed that the drug release behavior was closely followed to zero-order release kinetics. The pharmacokinetic studies were performed in rabbits with commercial controlled release tablets as reference, both preparations showed a sustained release effect. Compared with traditional preparation methods of OPCs, the new preparation process was simplified without the operation of laser drilling and the sealing process of capsule body and cap, which improved the feasibility of industrial production.

Advances in Oral Drug Delivery

The oral route is the most common route for drug administration. It is the most preferred route, due to its advantages, such as non-invasiveness, patient compliance and convenience of drug administration. Various factors govern oral drug absorption including drug solubility, mucosal permeability, and stability in the gastrointestinal tract environment. Attempts to overcome these factors have focused on understanding the physicochemical, biochemical, metabolic and biological barriers which limit the overall drug bioavailability. Different pharmaceutical technologies and drug delivery systems including nanocarriers, micelles, cyclodextrins and lipid-based carriers have been explored to enhance oral drug absorption. To this end, this review will discuss the physiological, and pharmaceutical barriers influencing drug bioavailability for the oral route of administration, as well as the conventional and novel drug delivery strategies. The challenges and development aspects of pediatric formulations will also be addressed.

Cyclosporine CsA—The Physicochemical Characterization of Liposomal and Colloidal Systems

This paper presents an overview of the possibilities of testing various cyclosporine (CsA) formulations with an emphasis on parameters that may be key to improving the stability and biocompatibility. The feasibility of CsA colloidal systems for oral (injection) administration were investigated using different techniques and compared with similar investigations of other researchers. The chosen CsA systems were developed using dipalmitoylphosphocholine (DPPC) and/or cholesterol as a lipid matrix, stabilized with ethanol, with soybean oil or n-tetradecane as oil phase in emulsions, under natural pH, room and physiological temperature. Their integrity was found to be strictly dependent on the stabilizers. The highest CsA penetrability with the system containing phospholipid in the context of its interactions with lipid membranes was shown. Also, the bioavailability of CsA can be enhanced with the biopolymer antibacterial chitosan. This mini-review suggests the suitability of liposome/microemulsion as promising vehicles for CsA delivery. The most hopeful proved to be formulation with the smaller particle size facilitating absorption, but when safety is assessed, relying on just the particle size cannot be the only criteria. Reassumed, the CsA formulation stability known on the basis of the size and zeta potential measurements guarantees a decrease of the individual variations in the drug bioavailability, toxicity and minimizes rejection.

Risk assessment and QbD based optimization of an Eprosartan mesylate nanosuspension: In-vitro characterization, PAMPA and in-vivo assessment

Quality by design (QbD) principles were implemented to understand the product and process variables of sonoprecipitation technique, for preparation of eprosartan mesylate (EM) nanosuspension. Quality risk management approach was utilized to identify and assess high-risk attributes affecting critical quality attributes (CQA's), prioritizing the number of experiments. The effect of critical material attributes (CMA's) and critical process parameters (CPP's) (soluplus concentration, drug concentration ultrasonication amplitude) on z-average particle size and PDI were investigated using a central composite face-centered design (CCF). Further, design space with criteria set of CMA's and CPP's was established to offer assurance of quality. The optimal formulation, identified using numerical optimization method, was further lyophilized and evaluated for redispersibility, solubility saturation, dissolution kinetic and in-vitro dissolution behavior. The EM nanoparticles were in an amorphous state as confirmed by differential scanning calorimetry (DSC) and X-ray diffraction (XRD) studies. The stability study conducted for a span of 6 months attests physical and chemical stability of EM dry nanosuspension in an amorphous state when stored at 4 °C. The enhanced solubility and in-vitro dissolution of EM nanosuspension may be attributed to the reduced particle size and alteration of the physical state from a crystalline to an amorphous state. Further, the optimized formulation was subjected to in-vitro and ex-vivo transport study using parallel artificial membrane permeability assay (PAMPA) and rat everted gut sac model respectively. The transport studies revealed successful permeation enhancement of EM nanoparticle when compared with EM API and physical mixture (PM). The absolute bioavailability of EM API was 7.1% and improved to 39.9% for EM nanosuspension, suggesting that nanoformulation had overcome solubility and permeability limited bioavailability which was observed with EM API.

A Single Dose of Baicalin Has No Clinically Significant Effect on the Pharmacokinetics of Cyclosporine A in Healthy Chinese Volunteers

Despite its narrow therapeutic window and large interindividual variability, cyclosporine A (CsA) is the first-line therapy following organ transplantation. Metabolized mainly by CYP3A and being a substrate of P-glycoprotein (P-gp), CsA is susceptible to drug–drug interactions. Baicalin (BG) is a drug used for adjuvant therapy of hepatitis in traditional Chinese medicine. Since its aglycone baicalein (B) inhibits CYP3A and P-gP, co-administration might affect CsA pharmacokinetics. This study investigated the effect of BG on CsA pharmacokinetics. In a two-period study, 16 healthy volunteers received a single 200 mg oral CsA dose alone (reference period) or in combination with 500 mg BG (test period). Pharmacokinetic evaluation of CsA was carried out using non-compartmental analysis (NCA) and population pharmacokinetics (popPK). Treatments were compared using the standard bioequivalence method. Based on NCA, 90% CIs of AUC and C_max test-to-reference ratios were within bioequivalence boundaries. In the popPK analysis, a two-compartment model (clearance/F 62.8 L/h, central and peripheral volume of distribution/F 254 L and 388 L) with transit compartments for absorption appropriately described CsA concentrations. No clinically relevant effect of 500 mg BG co-administration on CsA pharmacokinetics was identified and both treatments were well tolerated.

Potential of Lipid Nanoparticles (SLNs and NLCs) in Enhancing Oral Bioavailability of Drugs with Poor Intestinal Permeability

Lipid-based drug delivery systems has become a popular choice for oral delivery of lipophilic drugs with dissolution rate limited oral absorption. Lipids are known to enhance oral bioavailability of poorly water-soluble drugs in multiple ways like facilitating dissolution as micellar solution, enhancing the lymphatic uptake and acting as inhibitors of efflux transporters. Lipid nanoparticles are matrix type lipid-based carrier systems which can effectively encapsulate both lipophilic and hydrophilic drugs. Lipid nanoparticles namely solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC) are versatile drug delivery system and can be used for multiple routes of delivery like parenteral, topical, ocular, transdermal, and oral. Lipid nanoparticles are particularly attractive vehicles for peroral delivery of drugs with oral bioavailability problems as they are composed of lipid excipients which are cheap, easily available, and non-toxic; manufacturing technique is simple and readily scalable for large-scale production; the formulations provide controlled release of active components and have no stability issue. A large number of drugs have been incorporated into lipid nanoparticles with the objective of overcoming their poor oral bioavailability. This review tries to assess the potential of lipid nanoparticles for enhancing the oral bioavailability of drugs with permeability limited oral absorption such as drugs belonging to class IV of Biopharmaceutic Classification System (BCS) and protein and peptide drugs and also discusses the mechanism behind the bioavailability enhancement and safety issues related to such delivery systems.

Characterization and Stability of Amorphous Tadalafil and Four Crystalline Polymorphs

Tadalafil (TD), a phosphodiesterase-5 (PDE-5) inhibitor with poor oral bioavailability. The aim of the study was to prepare and characterize three crystalline polymorphs of TD (II, III, and IV) and the tadalafil amorphous form (TD-AM). TD polymorphs and TD-AM were prepared and characterized by polarized light microscope (PLM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), X-ray powder diffractometry (XRPD), and Fourier-transform (FT)IR, followed by the dissolution testing, physical stabilities and polymorphic transformation studies. TD-I and TD-II were found to be enantiotropically related, while TD-III was monotiotropically related to TD-I with heat release. Among all studied polymorphs, TD-AM demonstrated an extremely high intrinsic dissolution rate with most prolonged higher saturated concentration during dissolution, while TD-II, TD-III, and TD-IV converted to TD-I easily by supersaturation-mediated phase transformation. Upon heating under 60°C for 3 h and storing at long-term stability condition for 3 months, no phase transformation was detected for TD-I, TD-III, and TD-AM, while TD-II and TD-IV easily transformed to TD-I and TD-III, respectively. The higher intrinsic dissolution rate, prolonged supersaturated state during dissolution and favorable physical stability of TD-AM made it to be a very promising candidate for further product development.

Enhanced Dissolution and Oral Bioavailability of Cyclosporine A: Microspheres Based on αβ-Cyclodextrins Polymers

Cyclosporine (CsA) has a selective property of suppressing various T-lymphocyte functions. This is of utmost importance in preventing allograft rejection by several organ transplantations, as well as in the treatment of systemic and local autoimmune disorders. However, the poor water solubility of CsA can be a major hurdle for its absorption into the blood stream, which leads to low bioavailability and thus less efficacy. The aim of this study was to prepare, characterize, and evaluate in vitro as well as in vivo, the potential of the innovative CsA drug delivery system. The latter contains CsA in spherical amorphous solid dispersion (SASD) which is embedded in an original α-cyclodextrin and β-cyclodextrin polymer mixture (Poly-αβ-CD) as a multifunctional amorphous carrier. The new developed SASD formulation showed that CsA was molecularly dispersed in αβ-cyclodextrins in an amorphous form, as was confirmed by physicochemical characterization studies. Interestingly, the peptide secondary structure, and thus, the drug activity was not impacted by the preparation of SASD as was shown by circular dichroism. Furthermore, the in vitro CsA release profile kinetics was almost identical to the commercially available product Neoral^®. This study presents the first in vivo proof-of-concept for a novel drug delivery system based on Poly-αβ-CD containing CsA, with SASD allowing for increased bioavailibility. The pharmacokinetic parameters of cyclosporine A from the spherical spray-dried dispersion formulation was demonstrated in a “rat” animal model. For comparison, the commercially available Neoral® was studied. Importantly, the pharmacokinetic parameters were improved by extending T_max from 2 to 3 h after the oral administration in rats, and eventually preventing the enterohepatic circulation. All these results clearly demonstrate the improved pharmacokinetic parameters and enhanced bioavailability of CsA in the new developed drug delivery system. These data demonstrated the superiority of the newly developed Poly-αβ-CD formulation for oral administration of the poorly soluble CsA in vivo without altering its secondary structure. Poly-αβ-CD can be a very useful tool for the oral administration of poorly water-soluble drugs.

Physicochemical and biopharmaceutical characterization of celecoxib nanoparticle: Avoidance of delayed oral absorption caused by impaired gastric motility

The present study aimed to develop a celecoxib (CEL) nanoparticle with improved dissolution/dispersion and consistent absorption even in the presence of impaired gastric motility. CEL was pulverized by a wet-milling with hydroxypropyl cellulose (HPC), and the prepared nanoparticles were physicochemically characterized after freeze-drying. CEL nanoparticle with HPC-SSL (NP/CEL) exhibited better dissolution/dispersion behavior in pH1.2 solution compared with CEL nanoparticles with other polymers, as evidenced by a 21.8-fold higher initial dissolution/dispersion rate than crystalline CEL. The mean particle diameter of water suspended-NP/CEL was 250 nm, and the CEL nanoparticle existed in an amorphous state. Even after storage at 40 °C for 4 weeks, there were no significant changes in the dissolution/dispersion behavior. Oral absorption of CEL samples (5 mg-CEL/kg) was evaluated in normal and propantheline (PPT)-treated rats with simulated gastric motility impairment. In PPT-treated rats, oral crystalline CEL led to a decrease in oral absorption by 12% of the AUC_0-4 compared with that in normal rats, whereas NP/CEL suppressed the pharmacokinetic transition of CEL by 43% of the AUC_0-4 due to the improved dissolution/dispersion behavior of CEL. The NP/CEL system might be promising to avoid decreased absorption of CEL caused by impaired gastric motility.

Relationship between amorphous solid dispersion in vivo absorption and in vitro dissolution: phase behavior during dissolution, speciation, and membrane mass transport

Enzalutamide is a fast crystallizing, hydrophobic compound that has solubility limited absorption in vivo. Given the low aqueous solubility of this compound, it was of interest to evaluate amorphous formulations in vitro and in vivo. Amorphous solid dispersions (ASD) of enzalutamide were prepared with the hydrophilic polymers, hydroxypropyl methylcellulose acetate succinate (HPMCAS) and copovidone (PVPVA). A side-by-side diffusion cell was developed as an in vitro characterization tool to discriminate enzalutamide ASDs based upon the solute thermodynamic activity achieved during dissolution and its impact on the subsequent membrane transport rates, phase behavior, and drug speciation. The same formulations were then tested in vivo in rats using oral dosing of ASD suspensions. Different levels of plasma exposure were observed between the ASDs, which could be correlated to the phase behaviors of the ASDs following dissolution. Unsurprisingly, ASDs that underwent crystallization show lower plasma exposures. However, differences were also observed between ASDs that dissolved to form nanosized amorphous drug aggregates versus those that dissolved to yield only supersaturated solutions, with the former outperforming the latter in terms of the plasma exposure. These observations highlight the importance of thoroughly understanding the phase behavior of an amorphous formulation following dissolution and the need to discriminate between different types of precipitation, specifically crystallization versus glass liquid phase separation to form nanosized amorphous aggregates.

Pharmaceutical Applications of Cellulose Ethers and Cellulose Ether Esters

Cellulose ethers have proven to be highly useful natural-based polymers, finding application in areas including food, personal care products, oil field chemicals, construction, paper, adhesives, and textiles. They have particular value in pharmaceutical applications due to characteristics including high glass transition temperatures, high chemical and photochemical stability, solubility, limited crystallinity, hydrogen bonding capability, and low toxicity. With regard to toxicity, cellulose ethers have essentially no ability to permeate through gastrointestinal enterocytes and many are already in formulations approved by the U.S. Food and Drug Administration. We review pharmaceutical applications of these valuable polymers from a structure-property-function perspective, discussing each important commercial cellulose ether class; carboxymethyl cellulose, methyl cellulose, hydroxypropylcellulose, hydroxypropyl methyl cellulose, and ethyl cellulose, and cellulose ether esters including hydroxypropyl methyl cellulose acetate succinate and carboxymethyl cellulose acetate butyrate. We also summarize their syntheses, basic material properties, and key pharmaceutical applications.

Supramolecular nanofibers of dexamethasone derivatives to form hydrogel for topical ocular drug delivery

The low bioavailability exhibits by conventional ocular formulation owing to rapid precorneal clearance and lower corneal permeability can be overcame by the application of the gelling system. In the present study, a prodrug supramolecular hydrogel derived from succinated dexamethasone (Dex-SA) was fabricated using a pH hydrolytic strategy and explored as a "self-delivery" system for ophthalmic drugs. The self-assembled Dex-SA supramolecular hydrogel exhibited a typical nano-fibrous microstructure and was thixotropic. Both dexamethasone (Dex) and Dex-SA prodrug sustainably released from Dex-SA supramolecular hydrogel in a period of 120 h in vitro release study, and the initial pH value of hydrogel significantly influence on the release ratio of Dex/Dex-SA. Furthermore, the lyophilized Dex-SA supramolecular hydrogel displayed long-term stability without causing any apparent hydrolysis of Dex-SA at -20 °C over 30 day and quickly re-formed a hydrogel after dissolving into aqueous solution. The formed Dex-SA supramolecular hydrogel had lower cytotoxicity than Dex at drug concentration up to 2.5 mM, and exhibited a comparable anti-inflammatory efficacy to a Dex sodium phosphate (Dexp) aqueous solution in lipopolysaccharide-activated RAW264.7 macrophages. Topical instillation of the Dex-SA supramolecular hydrogel showed excellent intraocular biocompatibility and it was not an irritant in rabbit eyes. More importantly, the Dex-SA supramolecular hydrogel provided a prolonged precorneal retention and significantly enhanced the ocular bioavailability over Dexp aqueous solution after topical instillation. Overall, this work illustrates an effective approach for the development of prodrug supramolecular hydrogels to extend the precorneal retention and enhance ocular bioavailability of drugs after topical instillation.

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.

A Polyvinylpyrrolidone-Based Supersaturable Self-Emulsifying Drug Delivery System for Enhanced Dissolution of Cyclosporine A

A novel supersaturable self-emulsifying drug delivery system (S-SEDDS) of cyclosporine A (CyA)—a poorly water-soluble immunosuppressant—was constructed in order to attain an apparent concentration–time profile comparable to that of conventional SEDDS with reduced use of oil, surfactant, and cosolvent. Several hydrophilic polymers, including polyvinylpyrrolidone (PVP), were employed as precipitation inhibitors in the conventional SEDDS, which consists of corn oil-mono-di-triglycerides, polyoxyl 40 hydrogenated castor oil, ethanol, and propylene glycol. PVP-incorporated pre-concentrate (CyA:vehicle ingredients:PVP = 1:4.5:0.3 w/v/w) spontaneously formed spherical droplets less than 120 nm within 7 min of being diluted with water. In an in vitro dialysis test in a biorelevant medium such as simulated fed and/or fasted state intestinal and/or gastric fluids, PVP-based S-SEDDS exhibited a higher apparent drug concentration profile compared to cellulose derivative-incorporated S-SEDDS, even displaying an equivalent concentration profile with that of conventional SEDDS prepared with two times more vehicle (CyA:vehicle ingredients = 1:9 w/v). The supersaturable formulation was physicochemically stable under an accelerated condition (40 °C/75% RH) over 6 months. Therefore, the novel formulation is expected to be a substitute for conventional SEDDS, offering a supersaturated state of the poorly water-soluble calcinurin inhibitor with a reduced use of vehicle ingredients.

Amorphous solid dispersion of cyclosporine A prepared with fine droplet drying process: Physicochemical and pharmacokinetic characterization

The present study aimed to develop an amorphous solid dispersion (ASD) of cyclosporine A (CsA) by a fine droplet drying (FDD) process for improvement in oral absorption of CsA. CsA and hydroxypropyl cellulose-SSL were dissolved in 1,4-dioxane, and the solution was powdered by the FDD process to obtain the ASD formulation of CsA (ASD/CsA). The ASD/CsA was characterized in terms of morphology, particle size distribution, crystallinity, dissolution behavior, physicochemical stability, and pharmacokinetic behavior in rats. The ASD/CsA was obtained in the form of uniform spherical particles, and the span factor was calculated to be ca. 0.4. CsA in the formulation existed in an amorphous state. The ASD/CsA exhibited a higher dissolution behavior of CsA than amorphous CsA, whereas storage of the ASD/CsA under accelerated conditions led to impairment in the dissolution behavior. The constant release of CsA from non-aged ASD/CsA was observed during dissolution testing. After oral administration of CsA samples (10mg-CsA/kg) in rats, the ASD/CsA showed a high and sustained plasma concentration of CsA as evidenced by a 18-fold increase in the oral bioavailability of CsA compared with amorphous CsA. From these findings, the FDD process might be an efficacious option for the ASD formulation of CsA with enhanced biopharmaceutics properties.

Amorphous powders for inhalation drug delivery

For inhalation drug delivery, amorphous powder formulations offer the benefits of increased bioavailability for poorly soluble drugs, improved biochemical stability for biologics, and expanded options of using various drugs and their combinations. However, amorphous formulations usually have poor physicochemical stability. This review focuses on inhalable amorphous powders, including the production methods, the active pharmaceutical ingredients and the excipients with a highlight on stabilization of the particles.

Use of Polyvinyl Alcohol as a Solubility-Enhancing Polymer for Poorly Water Soluble Drug Delivery (Part 1)

Polyvinyl alcohol (PVAL) has not been investigated in a binary formulation as a concentration-enhancing polymer owing to its high melting point/high viscosity and poor organic solubility. Due to the unique attributes of the KinetiSol® dispersing (KSD) technology, PVAL has been enabled for this application and it is the aim of this paper to investigate various grades for improvement of the solubility and bioavailability of poorly water soluble active pharmaceutical ingredients. Solid amorphous dispersions were created with the model drug, itraconazole (ITZ), at a selected drug loading of 20%. Polymer grades were chosen with variation in molecular weight and degree of hydroxylation to determine the effects on performance. Differential scanning calorimetry, powder X-ray diffraction, polarized light microscopy, size exclusion chromatography, and dissolution testing were used to characterize the amorphous dispersions. An in vivo pharmacokinetic study in rats was also conducted to compare the selected formulation to current market formulations of ITZ. The 4-88 grade of PVAL was determined to be effective at enhancing solubility and bioavailability of itraconazole.

Physicochemical stability study on cyclosporine A loaded dry-emulsion formulation with enhanced solubility

The main purpose of the present study was to evaluate the physicochemical stability of cyclosporine A (CsA)-loaded glycerol monooleate-based dry emulsion (DE). DE formulations containing 5-25% CsA (DE5-25) were stored at 25°C/60% relative humidity for 4 weeks, and freeze-dried solid dispersion formulations containing 5-30% CsA (FD5-30) were also prepared as reference formulations. Even after the storage, no significant changes were observed in the appearance of any formulations. In the dissolution study, both DE and FD exhibited marked enhancement of solubility and there was at least 2.0-fold improvement in the initial dissolution rate of DE formulations compared with that of FD formulations. After storage, DE5, DE15 and FD5 maintained relatively high solubility, with 10% reduction compared with the initial state. However, the solubility of DE25 gradually decreased during storage, as evidenced by 76% reduction of the dissolution amount. No significant changes were seen in DE5-25 using powder X-ray diffraction, although thermal analysis revealed moderate changes in crystallinity in DE25 after storage, possibly leading to the decreased dissolution. Furthermore, particle size distributions of micelles in DE5 and DE15 were almost unchanged after storage for 4 weeks. From these findings, it appears that the physicochemical stability of CsA-loaded DE might vary depending on the manufacturing method and that further optimization could improve physical properties and stability.

Sylysia 350/Eudragit S100 solid nanomatrix as a promising system for oral delivery of cyclosporine A

Cyclosporine A (CyA) is a poorly soluble peptide and the available preparation is the surfactant based Sandimmum Neoral(®). In this study, we developed a novel pH-sensitive nanomatrix system of CyA with medical-grade nanoporous silica and Eudragit(®) to enhance the oral absorption of CyA as well as to improve the potential nephrotoxicity caused by the pronounced initial plasma peak of Neoral(®). The nanomatrixs were prepared by an absolutely simple conventional process. The scanning electron microscopy (SEM), X-ray powder diffraction analysis (XRD), differential thermal analysis (DSC) and specific surface area and pore size analysis were used to analyze the physicochemical characterization of the nanomatrix. The nanomatrix, consisted of CyA, Eudragit(®) S100 and Sylysia 350 (1/5/5, w/w/w %), not only increased the dissolution of CyA in vitro but also exhibited excellent enteric behavior. The characterization of CyA nanomatrix showed the CyA was highly dispersed in the nanomatrix in a molecular or amorphous state and partly filled into the nanopores of Sylysia 350. The results of comparative pharmacokinetic study showed that the optimized nanomatrix had a relative bioavailability of 90.8% with Neoral(®) but a lower Cmax than that of Neoral(®). In conclusion, the novel nanomatrix of CyA, composed of pharmaceutical excipients of biological safety and easily prepared, is expected to become a promising marketed product for the oral delivery of CyA.

Enhancement of oral bioavailability of cyclosporine A: comparison of various nanoscale drug-delivery systems

A variety of nanoscale delivery systems have been shown to enhance the oral absorption of poorly water-soluble and poorly permeable drugs. However, the performance of these systems has seldom been evaluated simultaneously. The aim of this study was to compare the bioavailability enhancement effect of lipid-based nanocarriers with poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) to highlight the importance of the lipid composition, with cyclosporine A (CyA) as a model drug. CyA-loaded PLGA NPs, nanostructured lipid carriers (NLCs), and self-microemulsifying drug-delivery systems (SMEDDS) were prepared. The particle size of PLGA NPs (182.2±12.8 nm) was larger than that of NLCs (89.7±9.0 nm) and SMEDDS (26.9±1.9 nm). All vehicles are charged negatively. The entrapment efficiency of PLGA NPs and NLCs was 87.6%±1.6% and 80.3%±0.6%, respectively. In vitro release tests indicated that the cumulative release of CyA was lower than 4% from all vehicles, including Sandimmun Neoral^®, according to the dialysis method. Both NLCs and SMEDDS showed high relative oral bioavailability, 111.8% and 73.6%, respectively, after oral gavage administration to beagle dogs, which was not statistically different from commercial Sandimmun Neoral^®. However, PLGA NPs failed to achieve efficient absorption, with relative bioavailability of about 22.7%. It is concluded that lipid-based nanoscale drug-delivery systems are superior to polymeric NPs in enhancing oral bioavailability of poorly water-soluble and poorly permeable drugs.

Solubility and dissolution enhancement strategies: current understanding and recent trends

Identification of lead compounds with higher molecular weight and lower aqueous solubility has become increasingly prevalent with the advent of high throughput screening. Poor aqueous solubility of these lipophilic compounds can drastically affect the dissolution rate and subsequently the drug absorbed in the systemic circulation, imposing a significant burden of time and money during drug development process. Various pre-formulation and formulation strategies have been applied in the past that can improve the aqueous solubility of lipophilic compounds by manipulating either the crystal lattice properties or the activity coefficient of a solute in solution or both, if possible. However, despite various strategies available in the armor of formulation scientist, solubility issue still remains an overriding problem in the drug development process. It is perhaps due to the insufficient conceptual understanding of solubility and dissolution phenomenon that hinders the judgment in selecting suitable strategy for improving aqueous solubility and/or dissolution rate. This article, therefore, focuses on (i) revisiting the theoretical and mathematical concepts associated with solubility and dissolution, (ii) their application in making rationale decision for selecting suitable pre-formulation and formulation strategies and (iii) the relevant research performed in this field in past decade.

[Strategic formulation study on dry powder inhalation system based on modulated molecular properties and controlled pharmacokinetics]

Cyclosporine A (CsA) has been widely used as an immunosuppressive agent, and recent outcomes from clinical studies are indicative of the potent therapeutic potential of CsA for chronic asthma and airway inflammation. The clinical use of CsA for airway inflammatory diseases is partly limited because of low oral bioavailability and severe systemic side effects. A number of CsA dosage forms have been proposed to overcome these drawbacks, for example, nebulizer formulation and metered-dose inhaler formulation for inhalation therapy, whereas these liquid formulations sometimes contain organic solvents and other solubilizers, leading to local irritant potency. In this context, our group developed a dry powder inhalation (DPI) system of CsA, employing a polymer-based amorphous solid dispersion (ASD) approach, for inhalation therapy on airway inflammations. There was marked improvement in dissolution behavior of the ASD formulation compared with that of an amorphous CsA. The new DPI system of CsA exhibited high dispersibility and suitable particle distribution for inhalation therapy. In vivo experiments demonstrated that inhaled DPI system of CsA attenuated inflammatory events in experimental asthma/chronic obstructive pulmonary disease (COPD) model rats as evidenced by a decrease of infiltrated granulocytes, and there was no excessive increase in systemic exposure of CsA at a pharmacologically effective dose, possibly leading to reduced systemic side effects. From these findings, combination use of CsA-loaded ASD and DPI systems might be a promising approach for the treatment of airway inflammatory diseases with improved pharmacodynamics and lower systemic exposure.

Polymeric micelles and alternative nanonized delivery vehicles for poorly soluble drugs

Poorly soluble drugs often encounter low bioavailability and erratic absorption patterns in the clinical setting. Due to the rising number of compounds having solubility issues, finding ways to enhance the solubility of drugs is one of the major challenges in the pharmaceutical industry today. Polymeric micelles, which form upon self-assembly of amphiphilic macromolecules, can act as solubilizing agents for delivery of poorly soluble drugs. This manuscript examines the fundamentals of polymeric micelles through reviews of representative literature and demonstrates possible applications through recent examples of clinical trial developments. In particular, the potential of polymeric micelles for delivery of poorly water-soluble drugs, especially in the areas of oral delivery and in cancer therapy, is discussed. Key considerations in utilizing polymeric micelles' advantages and overcoming potential disadvantages have been highlighted. Lastly, other possible strategies related to particle size reduction for enhancing solubilization of poorly water-soluble drugs are introduced.