Enhanced supersaturation and oral absorption of sirolimus using an amorphous solid dispersion based on Eudragit® e

Ternary Solid Dispersions: A Review of the Preparation, Characterization, Mechanism of Drug Release, and Physical Stability

The prevalence of active pharmaceutical ingredients (APIs) with low water solubility has experienced a significant increase in recent years. These APIs present challenges in formulation, particularly for oral dosage forms, despite their considerable therapeutic potential. Therefore, the improvement of solubility has become a major concern for pharmaceutical enterprises to increase the bioavailability of APIs. A promising formulation approach that can effectively improve the dissolution profile and the bioavailability of poorly water-soluble drugs is the utilization of amorphous systems. Numerous formulation methods have been developed to enhance poorly water-soluble drugs through amorphization systems, including co-amorphous formulations, amorphous solid dispersions (ASDs), and the use of mesoporous silica as a carrier. Furthermore, the successful enhancement of certain drugs with poor aqueous solubility through amorphization has led to their incorporation into various commercially available preparations, such as ASDs, where the crystalline structure of APIs is transformed into an amorphous state within a hydrophilic matrix. A novel approach, known as ternary solid dispersions (TSDs), has emerged to address the solubility and bioavailability challenges associated with amorphous drugs. Meanwhile, the introduction of a third component in the ASD and co-amorphous systems has demonstrated the potential to improve performance in terms of solubility, physical stability, and processability. This comprehensive review discusses the preparation and characterization of poorly water-soluble drugs in ternary solid dispersions and their mechanisms of drug release and physical stability.

Liposomal Formulation for Oral Delivery of Cyclosporine A: Usefulness as a Semisolid-Dispersion System

PURPOSE

This study aims to understand the process and mechanism of oral drug absorption from liposomes and to verify the usefulness of liposomal formulation for poorly soluble drugs.

METHODS

Cyclosporine A (CsA) was used as a model drug and entrapped into Dipalmitoylphosphatidylcholine (DPPC) and distearoylphosphatidylcholine (DSPC) liposomes. Molecular state of CsA in the liposomes was analyzed using powder X-ray diffraction (PXRD) and polarized light microscopy (PLM). Release profiles of CsA from liposomes were observed in fasted state simulated intestinal fluid (FaSSIF). Oral absorption of CsA from liposomal formulations were investigated in rats.

RESULTS

PXRD and PLM analyses suggested that CsA exists in the lipid layer of liposomes as a molecular dispersed state. Although both liposomes retained CsA stably in the simple buffer, DPPC liposomes quickly released CsA within 10 min in FaSSIF due to the interaction with bile acid. In contrast, effect of bile acid was negligible in DSPC, indicating a high resistivity to membrane perturbation. Oral bioavailability of CsA from liposomal formulations were almost comparable with that from a marketed product (Neoral). However, the absorption profiles were clearly different. CsA was absorbed quickly from DPPC liposomes and Neoral, while sustained absorption profile was observed from DSPC liposomes. Further study in which ritonavir was co-entrapped in the liposomes with CsA showed the higher efficacy of ritonavir to increase oral bioavailability of CsA.

CONCLUSION

Liposomes allows the appropriate formulation design for oral delivery of poorly soluble drugs, not only to increase the extent but also to control the rate of absorption.

The Topical Ocular Delivery of Rapamycin to Posterior Eye Tissues and the Suppression of Retinal Inflammatory Disease

Treatment of posterior eye diseases with intravitreal injections of drugs, while effective, is invasive and associated with side effects such as retinal detachment and endophthalmitis. In this work, we have formulated a model compound, rapamycin (RAP), in nanoparticle-based eye drops and evaluated the delivery of RAP to the posterior eye tissues in a healthy rabbit. We have also studied the formulation in experimental autoimmune uveitis (EAU) mouse model with retinal inflammation. Aqueous RAP eye drops were prepared using N-palmitoyl-N-monomethyl-N,N-dimethyl-N,N,N-trimethyl-6-O-glycolchitosan (Molecular Envelope Technology - MET) containing 0.23 ± 0.001% w/v RAP with viscosity, osmolarity, and pH within the ocular comfort range, and the formulation (MET-RAP) was stable in terms of drug content at both refrigeration and room temperature for one month. The MET-RAP eye drops delivered RAP to the choroid-retina with a Cmax of 145 ± 49 ng/g (tmax = 1 hour). The topical application of the MET-RAP eye drops to the EAU mouse model resulted in significant disease suppression compared to controls, with activity similar to dexamethasone eye drops. The MET-RAP eye drops also resulted in a reduction of RORγt and an increase in both Foxp3 expression and IL-10 secretion, indicating a mechanism involving the inhibition of Th17 cells and the up-regulation of T-reg cells. The MET-RAP formulation delivers RAP to the posterior eye segments, and the formulation is active in EAU.

Polyelectrolyte Matrices in the Modulation of Intermolecular Electrostatic Interactions for Amorphous Solid Dispersions: A Comprehensive Review

Polyelectrolyte polymers have been widely used in the pharmaceutical field as excipients to facilitate various drug delivery systems. Polyelectrolytes have been used to modulate the electrostatic environment and enhance favorable interactions between the drug and the polymer in amorphous solid dispersions (ASDs) prepared mainly by hot-melt extrusion. Polyelectrolytes have been used alone, or in combination with nonionic polymers as interpolyelectrolyte complexes, or after the addition of small molecular additives. They were found to enhance physical stability by favoring stabilizing intermolecular interactions, as well as to exert an antiplasticizing effect. Moreover, they not only enhance drug dissolution, but they have also been used for maintaining supersaturation, especially in the case of weakly basic drugs that tend to precipitate in the intestine. Additional uses include controlled and/or targeted drug release with enhanced physical stability and ease of preparation via novel continuous processes. Polyelectrolyte matrices, used along with scalable manufacturing methods in accordance with green chemistry principles, emerge as an attractive viable alternative for the preparation of ASDs with improved physical stability and biopharmaceutic performance.

Ternary solid dispersions: classification and formulation considerations

The number of active pharmaceutical compounds from the biopharmaceutical classification system (BCS) belonging to Class II and IV have significantly increased in recent years. These compounds have high therapeutic potential but are difficult to formulate as oral dosage forms due to their poor aqueous solubility. The solubility and bioavailability of these poorly water-soluble compounds can be increased by various formulation approaches, such as amorphous solid dispersions (ASD), salt formation, complexations, etc. Out of these techniques, the ASD approach, where compounds are converted into amorphous form and embedded in the hydrophilic matrix, have been successfully used in many marketed preparations. The recent advancement of this ASD approach is the design of ternary solid dispersions (TSD), where an additional component is added to further improve their performance in terms of solubility, stability, and processability. This review discusses the classification, mechanism of performance improvement, preparation techniques, and characterizations for TSD.

Development of Apremilast Solid Dispersion Using TPGS and PVPVA with Enhanced Solubility and Bioavailability

Apremilast (APST) is an effective inhibitor of phosphodieasterase 4 (PDE4) which is the first oral drug for the treatment of adult patients with active psoriatic arthritis. However, Apremilast^'s low solubility restricts its dissolution and bioavailability. In this study, APST solid dispersion with D-α-tocopherol polyethylene glycol 1000 succinate (TPGS) and Poly(1-vinylpyrrolidone-co-vinyl acetate) (PVPVA) was developed to improve the dissolution and bioavailability of APST by spray drying. A series of TPGS were synthesized to elucidate the effect of the ratio of monoester to diester on solubilizing capacity. X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC), and Fourier transform infrared spectrophotometry (FT-IR) were used to characterize the solid dispersion, and the results showed that APST was amorphous in solid dispersion. In vitro dissolution study showed that the dissolution rate of solid dispersion in phosphate buffered saline (pH 6.8) was remarkably increased, reaching a release of 90% within 10 min. Moreover, in vivo pharmacokinetics study revealed that the bioavailability of solid dispersion in rats had significant improvement. In particular, its C_max and AUC_last were nearly 22- and 12.9-fold greater as compared to APST form B, respectively. In conclusion, APST solid dispersion with TPGS and PVPVA is an alternative drug delivery system to improve the solubility and oral bioavailability of APST.

Investigating crystallization tendency, miscibility, and molecular interactions of drug-polymer systems for the development of amorphous solid dispersions

Crystallization tendencies, thermal analysis [i.e. glass transition temperature (T_g)], crystallinity, and melting point depression, along with theoretical calculations such as solubility parameter, of five different drugs [i.e. curcumin (CUR), indomethacin (IND), flutamide (FLU), dipyridamole (DIP), and griseofulvin (GRI)] in the absence and presence of four different polymers in various drug-polymer ratios were determined and analyzed. Physical states of the drug in the solid dispersions (SDs) and their stability were characterized by X-ray diffraction and modulated differential scanning calorimetry. Infrared (IR) and Raman were used in selected systems (i.e. CUR, DIP, and GRI systems) to explore the role of drug-polymer interactions in the amorphization of SDs. The crystallization tendencies of pure drugs were categorized as low (CUR, IND), moderate (FLU), and high (DIP, GRI). In the presence of selected polymers, the crystallization tendency of the drugs changed, though a high polymer concentration was required for high crystallization-tendency drugs [i.e. DIP and GRI (>50% w/w)]. Polymers showing a greater effect on the crystallization tendency of drugs were found to have higher drug-polymer miscibility and stronger molecular interactions. Drug-polymer systems selected from the investigation of physical mixtures formed stable amorphous solid dispersions (ASD). Furthermore, the rank order of the crystallization tendency of drug-polymer systems correlated well with those on miscibility and molecular interactions. Those rank orders also correlated well with the stability of prepared/reported SDs. Hence, the developed approach has significant potential to be a rational screening method for the development of amorphous SDs.

Enhanced Oral Bioavailability of Resveratrol by Using Neutralized Eudragit E Solid Dispersion Prepared via Spray Drying

In this study, we designed amorphous solid dispersions based on Eudragit E/HCl (neutralized Eudragit E using hydrochloric acid) to maximize the dissolution of trans-resveratrol. Solid-state characterization of amorphous solid dispersions of trans-resveratrol was performed using powder X-ray diffraction, scanning electron microscopy, and particle size measurements. In addition, an in vitro dissolution study and an in vivo pharmacokinetic study in rats were carried out. Among the tested polymers, Eudragit E/HCl was the most effective solid dispersion for the solubilization of trans-resveratrol. Eudragit E/HCl significantly inhibited the precipitation of trans-resveratrol in a pH 1.2 dissolution medium in a dose-dependent manner. The amorphous Eudragit E/HCl solid dispersion at a trans-resveratrol/polymer ratio of 10/90 exhibited a high degree of supersaturation without trans-resveratrol precipitation for at least 48 h by the formation of Eudragit E/HCl micelles. In rats, the absolute oral bioavailability (F%) of trans-resveratrol from Eudragit E/HCl solid dispersion (10/90) was estimated to be 40%. Therefore, trans-resveratrol-loaded Eudragit E/HCl solid dispersions prepared by spray drying offer a promising formulation strategy with high oral bioavailability for developing high-quality health supplements, nutraceutical, and pharmaceutical products.

Preparation and characterization of sorafenib-loaded microprecipitated bulk powder for enhancing oral bioavailability

The aim of this study was to prepare and evaluate Eudragit-based microprecipitated bulk powder (MBP) formulations to enhance the oral bioavailability of sorafenib. Cationic Eudragit E PO and anionic Eudragit S100 were selected for MBP preparation. Ursodeoxycholic acid (UDCA)-incorporated MBP was also prepared to study the synergistic effect of UDCA in enhancing the bioavailability of sorafenib. Sorafenib-loaded MBPs were successfully prepared by a pH-controlled precipitation method using an aqueous antisolvent. Submicron-sized particles of MBPs were observed by scanning electron microscopy, and the amorphous form of sorafenib in MBPs was confirmed by powder X-ray diffraction. MBPs of cationic and anionic Eudragits showed different in vitro dissolution and pharmacokinetic profiles in rats. Sorafenib in Eudragit E PO-based MBP (E PO-MBP) was rapidly dissolved at low pH conditions (pH 1.2 and 4.0), but was precipitated again at pH 4.0 within 4 h. Dissolution of sorafenib from Eudragit S100-based MBP (S100-MBP) was high at pH 7.4 and did not precipitate for up to 4 h. After oral administration to rats, all MBPs, compared with powder, improved the oral absorption of sorafenib, with S100-MBP showing 1.5-fold higher relative oral bioavailability than E PO-MBP. Moreover, incorporation of UDCA in S100-MBP (S100-UDCA-MBP) further increased the C_max and oral bioavailability of sorafenib, although the dissolution was not significantly different from that of S100-MBP. Taken together, Eudragit-based MBP formulations could be a promising strategy for enhancing the oral bioavailability of sorafenib.

Potential of solid dispersions to enhance solubility, bioavailability, and therapeutic efficacy of poorly water-soluble drugs: newer formulation techniques, current marketed scenario and patents

In the last few decades, solid dispersion (SD) technology had been studied as an approach to produce an amorphous carrier to enhance the solubility, dissolution rate, and bioavailability of poorly water-soluble drugs. The use of suitable carrier and methodology in the preparation of SDs play a significant role in the biological behavior of the SDs. SDs have been prepared using a variety of pharmaceutically acceptable polymers utilizing various novel technologies. In the recent years, much attention has been paid toward the use of novel carriers and methodologies in exploring novel types of SDs to enhance therapeutic efficacy and bioavailability. The use of novel carriers and methodologies would be very beneficial for formulation scientists to develop some SDs-based formulations for their commercial use and clinical applications. In the present review, current literature of novel methodologies for SD preparation to enhance the dissolution rate, solubility, therapeutic efficacy, and bioavailability of poorly water-soluble drugs has been summarized and analyzed. Further, the current status of SDs, patent status, and future prospects have also been discussed.

Preparation, Characterization and Prevention of Auto-oxidation of Amorphous Sirolimus by Encapsulation in Polymeric Films Using Hot Melt Extrusion

BACKGROUND

Sirolimus (SIR) is a macrocyclic lactone antibiotic and used therapeutically as a potent immunosuppressant for prophylaxis of kidney transplant rejection. The development of an oral dosage form is challenging because of very poor aqueous solubility (2.6µg/ml). The oral bioavailability of SIR is only 15-20 % and is affected by food and other drugs. The main reasons for low bioavailability are intestinal degradation by enzymes especially by cytochrome P4503A4, efflux by P-glycoprotein and hepatic first-pass metabolism.

OBJECTIVE

The main objective was to prepare a mouth dissolving film dosage form of amorphous SIR to improve dissolution.

METHODS

Crystalline SIR was transformed to its form amorphous by milling for 2 h at room temperature. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and powder x-ray diffraction (PXRD) were used for characterisation. The stability of amorphous SIR was studied at 4°C and 40°C/75% RH. Amorphous SIR was formulated as oral films by melt extrusion with polyvinylpyrrolidone- vinyl acetate (PVP-VA), Soluplus® and hydroxypropyl cellulose (HPC) as carriers. The films were characterized for drug content, physical state, dissolution profile and stability at 4°C and 40°C/75% RH.

RESULTS

The PRXD and DSC confirmed the conversion of crystalline SIR to amorphous form by milling. The solubility of amorphous SIR was several folds higher than its crystalline form, but amorphous SIR was highly unstable at all tested temperatures (4° and 40°C). The extruded films exhibited higher dissolution and stability compared to milled SIR powder alone, but the process of extrusion had some detrimental effect on the chemical stability of amorphous SIR.

CONCLUSION

The film formulations showed a significant improvement in the storage stability of the amorphous form of SIR and the solubility advantage of the amorphous form was evident in the dissolution testing. The oral films can potentially improve the bioavailability of SIR by absorption through the buccal mucosa.

Characterization, Molecular Docking, and In Vitro Dissolution Studies of Solid Dispersions of 20(S)-Protopanaxadiol

In this study, we prepared solid dispersions (SDs) of 20(S)-protopanaxadiol (PPD) using a melting-solvent method with different polymers, in order to improve the solubility and dissolution performance of drugs with poor water solubility. The SDs were characterized via differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and molecular docking and dynamics study. DSC and PXRD results indicated that PPD crystallinity in SDs was significantly reduced, and that the majority of PPD is amorphous. No interaction was observed between PPD and polymers on FTIR and NMR spectra. Molecular docking and dynamic calculations indicated that the PPD molecule localized to the interpolated charged surface, rather than within the amorphous polymer chain network, which might help prevent PPD crystallization, consequently enhancing the PPD dispersion in polymers. An in vitro dissolution study revealed that the SDs considerably improved the PPD dissolution performance in distilled water containing 0.35% Tween-80 (T-80). Furthermore, among three PPD-SDs formulations, Poloxamer188 (F68) was the most effective in improving the PPD solubility and was even superior to the mixed polymers. Therefore, the SD prepared with F68 as a hydrophilic polymer carrier might be a promising strategy for improving solubility and in vitro dissolution performance. F68-based SD, containing PPD with a melting-solvent preparation method, can be used as a promising, nontoxic, quick-release, and effective intermediate for other pharmaceutical formulations, in order to achieve a more effective drug delivery.

Amorphous solid dispersions: Rational selection of a manufacturing process

Amorphous products and particularly amorphous solid dispersions are currently one of the most exciting areas in the pharmaceutical field. This approach presents huge potential and advantageous features concerning the overall improvement of drug bioavailability. Currently, different manufacturing processes are being developed to produce amorphous solid dispersions with suitable robustness and reproducibility, ranging from solvent evaporation to melting processes. In the present paper, laboratorial and industrial scale processes were reviewed, and guidelines for a rationale selection of manufacturing processes were proposed. This would ensure an adequate development (laboratorial scale) and production according to the good manufacturing practices (GMP) (industrial scale) of amorphous solid dispersions, with further implications on the process validations and drug development pipeline.