Supersaturated self-nanoemulsifying drug delivery systems (Super-SNEDDS) enhance the bioavailability of the poorly water-soluble drug simvastatin in dogs

Drug solubilization in dog intestinal fluids with and without administration of lipid-based formulations

The use of animal experiments can be minimized with computational models capable of reflecting the simulated environments. One such environment is intestinal fluid and the colloids formed in it. In this study we used molecular dynamics simulations to investigate solubilization patterns for three model drugs (carvedilol, felodipine and probucol) in dog intestinal fluid, a lipid-based formulation, and a mixture of both. We observed morphological transformations that lipids undergo due to the digestion process in the intestinal environment. Further, we evaluated the effect of bile salt concentration and observed the importance of interindividual variability. We applied two methods of estimating solubility enhancement based on the simulated data, of which one was in good qualitative agreement with the experimentally observed solubility enhancement. In addition to the computational simulations, we also measured solubility in i) aspirated dog intestinal fluid samples and ii) simulated canine intestinal fluid in the fasted state, and found there was no statistical difference between the two. Hence, a simplified dissolution medium suitable for in vitro studies provided physiologically relevant data for the systems explored. The computational protocol used in this study, coupled with in vitro studies using simulated intestinal fluids, can serve as a useful prescreening tool in the process of drug delivery strategies development.

Functionalized calcium carbonate (FCC) as a novel carrier to solidify supersaturated self-nanoemulsifying drug delivery systems (super-SNEDDS)

Functionalized calcium carbonate (FCC), a novel pharmaceutical excipient, has shown promising properties in the field of oral drug delivery. The current study aimed at evaluating the feasibility of FCC as a carrier for the solidification of self-nanoemulsifying drug delivery systems (SNEDDS) containing the poorly water-soluble model drug carvedilol (CRV). Conventional, subsaturated SNEDDS (80 %-SNEDDSliquid) and supersaturated SNEDDS (200 %-SNEDDSliquid) were loaded onto FCC via physical adsorption at three ratios; 2.5:1, 3.0:1 and 3.5:1 (w/w) of FCC:SNEDDSliquid, respectively, generating free-flowing powders (SNEDDSFCC) with drug loading ranging from 0.8 % to 2.6 % (w/w) CRV. The emulsification of SNEDDSFCC in a USP II dissolution setup (in purified water) was characterized using dynamic light scattering, resulting in similar droplet sizes and PDIs as observed for their liquid counterparts. The morphology and physical state of the obtained SNEDDSFCC were characterized using scanning electron microscopy and differential scanning calorimetry. The physical stability and drug release upon dispersion were assessed as a function of storage time. The 200 %-SNEDDSliquid were physically stable for 6 days, however, solidification using FCC stabilized the supersaturated concentrations of CRV for a test period of up to 10 weeks (solidification ratios 3.0:1 and 3.5:1 (FCC:SNEDDSliquid)). SNEDDSFCC achieved an improved rate and extent of drug release upon dispersion compared to the crystalline CRV in tap water (pH 7.5), however, to a lesser extent than their liquid counterparts. After 8 weeks of storage (25 °C at dry conditions), FCC was still able to rapidly release the SNEDDSliquid and demonstrated the same rate and extent of drug release as freshly prepared samples. The solidification of 200 %-SNEDDSliquid in presence of FCC greatly improved the drug loading and showed an enhanced drug release profile compared to the conventional systems. In conclusion, FCC showed potential as a carrier for solidification of SNEDDS and for the development of novel supersaturated solid SNEDDS for the oral delivery of poorly water-soluble drugs.

Lipid based formulations as supersaturating oral delivery systems: From current to future industrial applications

Lipid-based formulations, in particular supersaturated lipid-based formulations, are important delivery approaches when formulating challenging compounds, as especially low water-soluble compounds profit from delivery in a pre-dissolved state. In this article, the classification of lipid-based formulation is described, followed by a detailed discussion of different supersaturated lipid-based formulations and the recent advances reported in the literature. The supersaturated lipid-based formulations discussed include both the in situ forming supersaturated systems as well as the thermally induced supersaturated lipid-based formulations. The in situ forming drug supersaturation by lipid-based formulations has been widely employed and numerous clinically available products are on the market. There are some scientific gaps in the field, but in general there is a good understanding of the mechanisms driving the success of these systems. For thermally induced supersaturation, the technology is not yet fully understood and developed, hence more research is required in this field to explore the formulations beyond preclinical studies and initial clinical trials.

In Situ Monitoring of Drug Precipitation from Digesting Lipid Formulations Using Low-Frequency Raman Scattering Spectroscopy

Low-frequency Raman spectroscopy (LFRS) is a valuable tool to detect the solid state of amorphous and crystalline drugs in solid dosage forms and the transformation of drugs between different polymorphic forms. It has also been applied to track the solubilisation of solid drugs as suspensions in milk and infant formula during in vitro digestion. This study reports the use of LFRS as an approach to probe drug precipitation from a lipid-based drug delivery system (medium-chain self-nanoemulsifying drug delivery system, MC-SNEDDS) during in vitro digestion. Upon lipolysis of the digestible components in MC-SNEDDS containing fenofibrate as a model drug, sharp phonon peaks appeared at the low-frequency Raman spectral region (<200 cm^-1), indicating the precipitation of fenofibrate in a crystalline form from the formulation. Two multivariate data analysis approaches (principal component analysis and partial least squares discriminant analysis) and one univariate analysis approach (band ratios) were explored to track these spectral changes over time. The low-frequency Raman data produces results in good agreement with in situ small angle X-ray scattering (SAXS) measurements with all data analysis approaches used, whereas the mid-frequency Raman requires the use of PLS-DA to gain similar results. This suggests that LFRS can be used as a complementary, and potentially more accessible, technique to SAXS to determine the kinetics of drug precipitation from lipid-based formulations.

Supersaturating lipid-based solid dispersion of atazanavir provides enhanced solubilization and supersaturation in the digestive aqueous phase

Understanding and controlling the drug solubilization in digestive environment is of great importance in the design of lipid based solid dispersion (LBSD) for oral delivery of poorly aqueous soluble drugs. In the current study we determined the extent of drug solubilization and supersaturation of supersaturating lipid based solid dispersion which is governed by formulation variables like drug payload, lipid composition, solid carrier properties and lipid to solid carrier ratio. Initially, the impact of lipid chain length and drug payload on drug solubilization in lipid preconcentrate and dispersibility were evaluated to design liquid LbF of the model antiretroviral drug, atazanavir. The temperature induced supersaturation method enhanced the drug payload in medium chain triglyceride formulation at 60 °C. Further, the selected liquid supersaturated LbF was transformed into solid state LbF by employing different solid carriers including silica (Neusilin® US2 and Aerosil® 200), clay (Montmorillonite and Bentonite) and polymer (HPMC-AS and Kollidon® CL-M). The fabricated LBSDs were evaluated for solid state characterization to identify the physical nature of drug. In vitro digestion studies were conducted using pH-stat lipolysis method to assess the supersaturation propensity in aqueous digestive phase. Results revealed that LBSDs with silica and polymer carriers showed maximum drug solubilization throughout experiment compared to liquid LbF. The ionic interaction between drug-clay particles significantly reduced the ATZ partitioning from clay based LBSDs. LBSDs with dual purpose solid carrier like HPMC-AS and Neusilin® US2 offers the potential to improve drug solubilization of ATZ for physiologically relevant time. Lastly, we conclude that evaluation of formulation variables is crucial to achieve optimal performance of supersaturating LBSD.

The Influence of Blonanserin Supersaturation in Liquid and Silica Stabilised Self-Nanoemulsifying Drug Delivery Systems on In Vitro Solubilisation

Reformulating poorly water-soluble drugs as supersaturated lipid-based formulations achieves higher drug loading and potentially improves solubilisation and bioavailability. However, for the weak base blonanserin, silica solidified supersaturated lipid-based formulations have demonstrated reduced in vitro solubilisation compared to their liquid-state counterparts. Therefore, this study aimed to understand the influence of supersaturated drug load on blonanserin solubilisation from liquid and silica solidified supersaturated self-nanoemulsifying drug delivery systems (super-SNEDDS) during in vitro lipolysis. Stable liquid super-SNEDDS with varying drug loads (90-300% of the equilibrium solubility) were solidified by imbibition into porous silica microparticles (1:1 lipid: silica ratio). In vitro lipolysis revealed greater blonanserin solubilisation from liquid super-SNEDDS compared to solid at equivalent drug saturation levels, owing to strong silica-BLON/lipid interactions, evidenced by a significant decrease in blonanserin solubilisation upon addition of silica to a digesting liquid super-SNEDDS. An increase in solid super-SNEDDS drug loading led to increased solubilisation, owing to the increased drug:silica and drug:lipid ratios. Solidifying SNEDDS with silica enables the fabrication of powdered formulations with higher blonanserin loading and greater stability than liquid super-SNEDDS, however at the expense of drug solubilisation. These competing parameters need careful consideration in designing optimal super-SNEDDS for pre-clinical and clinical application.

Combining lipid based drug delivery and amorphous solid dispersions for improved oral drug absorption of a poorly water-soluble drug

Two widely applied enabling drug delivery approaches, self-nanoemulsifying drug delivery systems (SNEDDS) and amorphous solid dispersions (ASD), were combined, with the aim of enhancing physical stability, solubilization and absorption of the model drug ritonavir. Ritonavir was loaded at a concentration above its saturation solubility (S_eq) in the SNEDDS (superSNEDDS, 250% of S_eq). An ASD of ritonavir with polyvinylpyrrolidone-vinyl acetate copolymers (Kollidon® VA64) was prepared by ball milling. Relevant control formulations, which include conventional SNEDDS (90% of S_eq), superSNEDDS with a physical mix of Kollidon® VA64 and ritonavir (superSNEDDS+PM) and an aqueous suspension of ritonavir were used. A pharmacokinetic (PK) study in rats was performed to assess the relative bioavailability of ritonavir after oral administration. This was followed by evaluating the formulations in a novel two-step in vitro lipolysis model simulating rat gastric and intestinal conditions. The addition of a ritonavir containing ASD to superSNEDDS increased the degree of supersaturation from 250% to 275% S_eq in the superSNEDDS and the physical stability (absence of drug recrystallization) of the system from 48 h to 1 month under ambient conditions. The PK study in rats displayed significantly higher C_max and AUC_0-7h (3-fold increase) and faster T_max for superSNEDDS+ASD compared to the conventional SNEDDS whilst containing 3 times less lipid than the latter. Furthermore, superSNEDDS+ASD were able to keep the drug solubilised during in vitro lipolysis to the same degree as the conventional SNEDDS. These findings suggest that dissolving an ASD in a superSNEDDS can contribute to the development of novel oral delivery systems with increased bioavailability for poorly water-soluble drugs.

Multi-strategic approaches for enhancing active transportation using self-emulsifying drug delivery system

Oral delivery is the most desired route of drug administration and it can be more beneficial for patients suffering from chronic diseases wherein frequent parenteral administration of proteins such as insulin and calcitonin is required. The BCS class II drugs show low aqueous solubility and high permeability whereas BCS class IV drugs suffer from low aqueous solubility and low permeability. Additionally, biologic drugs are highly sensitive to presence of bioenzymes and bile salts when administered orally. Self-emulsifying drug delivery system (SEDDS) is a thermodynamically stable lipid formulation that enhances oral absorption of active ingredients via the opening of tight junctions, increasing the membrane fluidity, and thus overcomes the physiological barriers like viscous mucus layer, strong acid conditions and enzymatic degradation. An understanding of different theories that govern SEDDS formation and drug release can help in formulating a highly stable and effective drug delivery system. Poorly permeable drugs such as chlorpromazine require modification using methods like hydrophobic ion pairing, complexation with phospholipids, etc. to enable high entrapment efficiency which is discussed in the article. Additionally, the article gives an overview of the influence of polymers, length of fatty acids chain and zeta potential in enhancing permeation across the intestinal membrane.

Study and Computational Modeling of Fatty Acid Effects on Drug Solubility in Lipid-Based Systems

Lipid-based systems have many advantages in formulation of poorly water-soluble drugs but issues of a limited solvent capacity are often encountered in development. One of the possible solubilization approaches of especially basic drugs could be the addition of fatty acids to oils but currently, a systematic study is lacking. Therefore, the present work investigated apparently neutral and basic drugs in medium chain triglycerides (MCT) alone and with added either caproic acid (C6), caprylic acid (C8), capric acid (C10) or oleic acid (C18:1) at different levels (5 - 20%, w/w). A miniaturized solubility assay was used together with X-ray diffraction to analyze the residual solid and finally, solubility data were modeled using the conductor-like screening model for real solvents (COSMO-RS). Some drug bases had an MCT solubility of only a few mg/ml or less but addition of fatty acids provided in some formulations exceptional drug loading of up to about 20% (w/w). The solubility changes were in general more pronounced the shorter the chain length was and the longest oleic acid even displayed a negative effect in mixtures of celecoxib and fenofibrate. The COSMO-RS prediction accuracy was highly specific for the given compounds with root mean square errors (RMSE) ranging from an excellent 0.07 to a highest value of 1.12. The latter was obtained with the strongest model base pimozide for which a new solid form was found in some samples. In conclusion, targeting specific molecular interactions with the solute combined with mechanistic modeling provides new tools to advance lipid-based drug delivery.

Lipophilic Salts and Lipid-Based Formulations for Bridging the Food Effect Gap of Venetoclax

Lipid based formulations (LBF) have shown to overcome food dependent bioavailability for some poorly water-soluble drugs. However, the utility of LBFs can be limited by low dose loading due to a low drug solubility in LBF vehicles. This study investigated the solubility and drug loading increases in LBFs using lipophilic counterions to form lipophilic salts of venetoclax. Venetoclax docusate was formed from venetoclax free base and verified by ¹H NMR. Formation of stable venetoclax-fatty acid associations with either oleic acid or decanoic acid were attempted, however, the molecular associations were less consistent based on ¹H NMR. Venetoclax docusate displayed a up to 6.2-fold higher solubility in self-emulsifying drug delivery systems (SEDDS) when compared to the venetoclax free base solubility resulting in a higher dose loading. A subsequent bioavailability study in landrace pigs demonstrated a 2.5-fold higher bioavailability for the lipophilic salt containing long chain SEDDS compared to the commercially available solid dispersion Venclyxto® in the fasted state. The bioavailability of all lipophilic salt SEDDS in the fasted state was similar to Venclyxto® in the fed state. This study confirmed that lipophilic drug salts increase the dose loading in LBFs and showed that lipophilic salt-SEDDS combinations may be able to overcome bioavailability limitations of drugs with low inherent dose loading in lipid vehicles. Furthermore, the present study demonstrated the utility of a LBF approach, in combination with lipophilic salts, to overcome food dependent variable oral bioavailability of drugs.

Artificial Neural Networks to Predict the Apparent Degree of Supersaturation in Supersaturated Lipid-Based Formulations: A Pilot Study

In response to the increasing application of machine learning (ML) across many facets of pharmaceutical development, this pilot study investigated if ML, using artificial neural networks (ANNs), could predict the apparent degree of supersaturation (aDS) from two supersaturated LBFs (sLBFs). Accuracy was compared to partial least squares (PLS) regression models. Equilibrium solubility in Capmul MCM and Maisine CC was obtained for 21 poorly water-soluble drugs at ambient temperature and 60 °C to calculate the aDS ratio. These aDS ratios and drug descriptors were used to train the ML models. When compared, the ANNs outperformed PLS for both sLBF_Capmul^MC (r² 0.90 vs. 0.56) and sLBF_Maisine^LC (r² 0.83 vs. 0.62), displaying smaller root mean square errors (RMSEs) and residuals upon training and testing. Across all the models, the descriptors involving reactivity and electron density were most important for prediction. This pilot study showed that ML can be employed to predict the propensity for supersaturation in LBFs, but even larger datasets need to be evaluated to draw final conclusions.

Supersaturation and Solubilization upon In Vitro Digestion of Fenofibrate Type I Lipid Formulations: Effect of Droplet Size, Surfactant Concentration and Lipid Type

Lipid-based formulations (LBF) enhance oral drug absorption by promoting drug solubilization and supersaturation. The aim of the study was to determine the effect of the lipid carrier type, drop size and surfactant concentration on the rate of fenofibrate release in a bicarbonate-based in vitro digestion model. The effect of the lipid carrier was studied by preparing type I LBF with drop size ≈ 2 µm, based on medium-chain triglycerides (MCT), sunflower oil (SFO), coconut oil (CNO) and cocoa butter (CB). The drop size and surfactant concentration effects were assessed by studying MCT and SFO-based formulations with a drop size between 400 nm and 14 µm and surfactant concentrations of 1 or 10%. A filtration through a 200 nm filter followed by HPLC analysis was used to determine the aqueous fenofibrate, whereas lipid digestion was followed by gas chromatography. Shorter-chain triglycerides were key in promoting a faster drug release. The fenofibrate release from long-chain triglyceride formulations (SFO, CNO and CB) was governed by solubilization and was enhanced at a smaller droplet size and higher surfactant concentration. In contrast, supersaturation was observed after the digestion of MCT emulsions. In this case, a smaller drop size and higher surfactant had negative effects: lower peak fenofibrate concentrations and a faster onset of precipitation were observed. The study provides new mechanistic insights on drug solubilization and supersaturation after LBF digestion, and may support the development of new in silico prediction models.

Supersaturated LFCS type III self-emulsifying delivery systems of sorafenib tosylate with improved biopharmaceutical performance: QbD-enabled development and evaluation

The current studies investigate the application of quality by design-enabled type III self-emulsifying delivery system (Type III-SEDDS) of sorafenib tosylate (SFN) in improving its biopharmaceutical attributes. Initially, lipidic and emulsifying excipients were selected by carrying out solubility and phase titration experiments. After screening studies using Taguchi OA design, Type III-SEDDS were further optimised using D-optimal mixture design. The prepared formulations were assessed for globule size, zeta potential and percent of drug release. Following graphical optimisation, the optimum formulation was earmarked and further supersaturated to form saturated Type III-SEDDS (Sat-Type III-SEDDS) using a combination of HPMC and PVP to improve the stability of the formulation for a prolonged period. In vitro drug release of Type III-SEDDS study indicated approximately 8-fold improvement in dissolution rate over the pure powder drug. Cell uptake studies demonstrated higher uptake of dye-loaded Type III-SEDDS formulations in Caco-2 cells vis-à-vis plain dye. Cytotoxicity assay on Hep G2 cells revealed significant reduction in cell growth with Type III- and Sat-Type III-SEDDS vis-à-vis the pure drug. Furthermore, in situ permeation studies carried out using Wistar rats exhibited nearly 8.3- to 10.2-fold augmentation in permeation and absorption parameters of the drug from the Type III- and Sat-Type III-SEDDS, respectively, vis-à-vis the pure drug. Pharmacokinetic studies indicated nearly 3.98- and 3.62-fold improvement in AUC_0-72, and 8.01- and 5.42-fold in C_max, along with 0.25-fold decrease in T_max of the drug from Type III- and Sat-Type III-SEDDS, respectively, in comparison with the SFN suspension. Furthermore, high degree of level A linear correlation was established between fractions of drug dissolved (in vitro) and of drug absorbed (in vivo) at the corresponding time points for Sat-Type III-SEDDS and pure drug, whereas the Type III-SEDDS exhibited a nonlinear relationship. Stability studies indicated the robustness of Sat-Type III-SEDDS, when stored at 25 °C for 3 months. Overall, the manuscript documents the successful systematic development of SFN-loaded Sat-Type III-SEDDS with distinctly improved biopharmaceutical performance. Graphical abstract.

In Silico, In Vitro, and In Vivo Evaluation of Precipitation Inhibitors in Supersaturated Lipid-Based Formulations of Venetoclax

The concept of using precipitation inhibitors (PIs) to sustain supersaturation is well established for amorphous formulations but less in the case of lipid-based formulations (LBF). This study applied a systematic in silico–in vitro–in vivo approach to assess the merits of incorporating PIs in supersaturated LBFs (sLBF) using the model drug venetoclax. sLBFs containing hydroxypropyl methylcellulose (HPMC), hydroxypropyl methylcellulose acetate succinate (HPMCAS), polyvinylpyrrolidone (PVP), PVP-co-vinyl acetate (PVP/VA), Pluronic F108, and Eudragit EPO were assessed in silico calculating a drug–excipient mixing enthalpy, in vitro using a PI solvent shift test, and finally, bioavailability was assessed in vivo in landrace pigs. The estimation of pure interaction enthalpies of the drug and the excipient was deemed useful in determining the most promising PIs for venetoclax. The sLBF alone (i.e., no PI present) displayed a high initial drug concentration in the aqueous phase during in vitro screening. sLBF with Pluronic F108 displayed the highest venetoclax concentration in the aqueous phase and sLBF with Eudragit EPO the lowest. In vivo, the sLBF alone showed the highest bioavailability of 26.3 ± 14.2%. Interestingly, a trend toward a decreasing bioavailability was observed for sLBF containing PIs, with PVP/VA being significantly lower compared to sLBF alone. In conclusion, the ability of a sLBF to generate supersaturated concentrations of venetoclax in vitro was translated into increased absorption in vivo. While in silico and in vitro PI screening suggested benefits in terms of prolonged supersaturation, the addition of a PI did not increase in vivo bioavailability. The findings of this study are of particular relevance to pre-clinical drug development, where the high in vivo exposure of venetoclax was achieved using a sLBF approach, and despite the perceived risk of drug precipitation from a sLBF, including a PI may not be merited in all cases.

Exploring precipitation inhibitors to improve in vivo absorption of cinnarizine from supersaturated lipid-based drug delivery systems

Supersaturated lipid-based drug delivery systems are increasingly being explored as a bio-enabling formulation approach, particularly in preclinical evaluation of poorlywater-soluble drugs. While increasing the drug load through thermally-induced supersaturation resulted in enhanced in vivo exposure for some drugs, for others, such as cinnarizine, supersaturated lipid-based systems have not been found beneficial to increase the in vivo bioavailability. We hypothesized that incorporation of precipitation inhibitors to reduce drug precipitation may address this limitation. Therefore, pharmacokinetic profiles of cinnarizine supersaturated lipid-based drug delivery systems with or without precipitation inhibitors were compared. Five precipitation inhibitors were selected for investigation based on a high throughput screening of twenty-one excipients. In vivo results showed that addition of 5% precipitation inhibitors to long chain monoglyceride (LCM) or medium chain monoglyceride (MCM) formulations showed a general trend of increases in cinnarizine bioavailability, albeit only statistically significantly increased for Poloxamer 407 + LCM system (i.e. 2.7-fold increase in AUC_0-24h compared to LCM without precipitation inhibitors). It appeared that precipitation inhibitors mitigated the risk of in vivo precipitation of cinnarizine from sLBDDS and overall, bioavailability was comparable to that previously reported for cinnarizine after dosing of non-supersaturated lipid systems. In summary, for drugs which are prone to precipitation from supersaturated lipid-based drug delivery systems, such as cinnarizine, inclusion of precipitation inhibitors mitigates this risk and provides the opportunity to maximize exposure which is ideally suited in early efficacy and toxicology evaluation.

Improved Pharmacodynamic Potential of Rosuvastatin by Self-Nanoemulsifying Drug Delivery System: An in vitro and in vivo Evaluation

PURPOSE

The purpose of this proposed research was to investigate a nano-formulation developed using self-nanoemulsifying drug delivery system (SNEDDS) to improve the pharmacodynamic potential of rosuvastatin by assisting its transportation through lymphatic circulation.

METHODS

The utilized lipids, surfactants, and co-surfactants for SNEDDS were selected on the basis of solubility studies. The SNEDDS formulation was optimized by implementing a D-optimal mixture design, wherein the effect of concentration of Capmul MCM EP (X1), Tween 20 (X2) and Transcutol P (X3) as independent variables was studied on droplet size (Y1), % cumulative drug release (Y2) and self-emulsification time (Y3) as dependent variables. The optimized formulation was evaluated via in vitro parameters and in vivo pharmacodynamic potential in Wistar rats.

RESULTS

The D-optimal mixture design and subsequent ANOVA application resulted in the assortment of the optimized SNEDDS formulation that exhibited a droplet size of nano range (14.91nm), in vitro drug release of >90% within 30 minutes, and self-emulsification time of 16 seconds. The in vivo pharmacodynamic study carried out using Wistar rats confirmed the better antihyperlipidemic potential of developed formulation in normalizing the lipidic level of serum in contrast to pure drug and marketed tablets.

CONCLUSION

This research reports the application of D-optimal mixture design for successful and systematic development of rosuvastatin-loaded SNEDDS with distinctly enhanced in vitro and in vivo performance in comparison to marketed formulation. Eventually, improved anti-hyperlipidemic efficacy was envisaged which might be attributed to increased drug solubility and absorption. Overall, this study shows the utility of SNEDDS for improving the dissolution rate and bioavailability of poor aqueous-soluble drugs. The present SNEDDS formulation could be a promising approach and alternative to conventional dosage form.

The Influence of Solidification on the in vitro Solubilisation of Blonanserin Loaded Supersaturated Lipid-Based Oral Formulations

Supersaturated silica-lipid hybrids have previously demonstrated improved in vitro solubilisation and in vivo oral bioavailability of poorly water-soluble drugs, however were only fabricated using a single lipid (LFCS type I formulations) and were not compared to their liquid precursors. This study investigated the influence of lipid formulation classification (type I vs. type II vs. type IIIA/SNEDDS) and physical state (liquid LBF vs. solidified with silica) on the in vitro solubilisation of the poorly soluble, weak base, anti-psychotic drug, blonanserin (BLON), from a supersaturated lipid-based formulation (LBF). Stable liquid supersaturated LBF were fabricated using BLON (loaded at 150% of its equilibrium solubility), and solidified through encapsulation within porous silica microparticles at a 1:1 ratio. Their physicochemical properties and in vitro solubilisation during lipolysis were compared. Supersaturated BLON was encapsulated in the non-crystalline form. All supersaturated LBF improved the solubilisation of pure BLON during lipolysis regardless of their lipid formulation type or their physical state (1.7- to 13.4-fold). SNEDDS achieved greater solubilisation than the type II formulations (1.4- to 1.7-fold). Furthermore, the liquid precursors achieved greater solubilisation than the silica solidified formulations (4.5- to 5.7-fold). Additionally, in an attempt to increase BLON solubilisation, a spray-dried SNEDDS and dual-loaded solidified super-SNEDDS solidified with silica pre-loaded with BLON was developed, however did not significantly improve solubilisation. Liquid SNEDDS were identified as the optimal oral supersaturated LBF strategy for BLON based on in vitro lipolysis studies. Solidification of LBF using silica is a viable strategy for improving stability, however for drugs such as BLON, solidification may impede in vitro release and solubilisation.

Self-Nano-Emulsifying Drug-Delivery Systems: From the Development to the Current Applications and Challenges in Oral Drug Delivery

Approximately one third of newly discovered drug molecules show insufficient water solubility and therefore low oral bio-availability. Self-nano-emulsifying drug-delivery systems (SNEDDSs) are one of the emerging strategies developed to tackle the issues associated with their oral delivery. SNEDDSs are composed of an oil phase, surfactant, and cosurfactant or cosolvent. SNEDDSs characteristics, their ability to dissolve a drug, and in vivo considerations are determinant factors in the choice of SNEDDSs excipients. A SNEDDS formulation can be optimized through phase diagram approach or statistical design of experiments. The characterization of SNEDDSs includes multiple orthogonal methods required to fully control SNEDDS manufacture, stability, and biological fate. Encapsulating a drug in SNEDDSs can lead to increased solubilization, stability in the gastro-intestinal tract, and absorption, resulting in enhanced bio-availability. The transformation of liquid SNEDDSs into solid dosage forms has been shown to increase the stability and patient compliance. Supersaturated, mucus-permeating, and targeted SNEDDSs can be developed to increase efficacy and patient compliance. Self-emulsification approach has been successful in oral drug delivery. The present review gives an insight of SNEDDSs for the oral administration of both lipophilic and hydrophilic compounds from the experimental bench to marketed products.

Design and optimization of candesartan loaded self-nanoemulsifying drug delivery system for improving its dissolution rate and pharmacodynamic potential

During the last decades, much attention has been focused on SNEDDS approach to resolve concerns of BCS II class drugs with accentuation on upgrading the solubility and bioavailability. The present hypothesis confirms the theory that SNEDDS can reduce the impact of food on Candesartan solubilization, thereby offering the potential for improved oral delivery without co-administration with meals. The present studies describe quality-by-design-based development and characterization of Candesartan loaded SNEDDS for improving its pharmacodynamic potential. D-optimal mixture design was used for systematic optimization of SNEDDS, which showed globule size of 13.91 nm, more rapid drug release rate of >90% in 30 min and 16 s for self-emulsification. The optimized formulations were extensively evaluated, where an in vitro drug release study indicated up to 1.99- and 1.10-fold enhancement in dissolution rate from SNEDDS over pure drug and marketed tablet. In vivo pharmacodynamic investigation also showed superior antihypertensive potential of SNEDDS in normalizing serum lipid levels as compared to pure drug and marketed tablet that was executed on male Wistar rats. Overall, this paper reports successful systematic development of candesartan-loaded SNEDDS with distinctly improved biopharmaceutical performance. This research work interpreted a major role of SNEDDS for enhancing the rate of dissolution and bioavailability of poorly water soluble drugs.

Enhanced oral bioavailability of Bisdemethoxycurcumin-loaded self-microemulsifying drug delivery system: Formulation design, in vitro and in vivo evaluation

In this study, we sought to overcome the poor solubility and bioavailability of bismethoxycurcumin (BDMC) by fabricating a BDMC-loaded self micro-emulsifying system (BDMC-SMEDDS). Solubility and compatibility tests, pseudo-ternary phase diagrams (PTPDs) as well as d-optimal concept was applied to design the formulation. The assessment of the prepared BDMC-SMEDDS in-vitro mainly included droplet size (DS) and entrapment efficiency (EE) determination, morphology, drug release and stability testing. Besides, the in vivo behavior was also evaluated after oral administration of BDMC-SMEDDS to rats. The optimal formulation was found to compose of Kolliphor EL (K-EL, emulsifier, 645.3 mg), PEG 400 (co-emulsifier, 147.2 mg), ethyl oleate (EO, oil, 207.5 mg) and BDMC (50 mg). The BDMC-SMEDDS with satisfactory stability had a mean size of 21.25 ± 3.23 nm and EE of 98.31 ± 0.32%. Roughly 70% of BDMC was released from BDMC-SMEDDS within 84 h compared with <20% from the free BDMC. More importantly, the in-vivo behavior of BDMC-SMEDDS showed that the AUC_(0-12h) and plasma concentration of BDMC increased substantially as compared to the free BDMC. Altogether, BDMC-SMEDDS has the potential to enhance the solubility and bioavailability of BDMC and could be applied in the clinics.

A safety, tolerability, and pharmacokinetic study of a novel simvastatin silica-lipid hybrid formulation in healthy male participants

Simvastatin (SIM) is a commonly used cholesterol-lowering drug that can reduce the risk of major cardiovascular events. However, due to its poor intrinsic water solubility, the drug is poorly absorbed from the gastrointestinal tract and exhibits a low oral bioavailability of approximately 5%. The aim of this study was to fabricate and optimize SIM encapsulated silica-lipid hybrids (SLH) as a solid-state lipid-based formulation to enhance absorption and bioavailability during a human in vivo pharmacokinetic study. SLH formulations were formulated by spray drying a submicron emulsion with either Aerosil® 300 fumed silica nanoparticles (SLH-A) or Syloid® 244 amorphous micronized silica (SLH-B). A cross-over, double-blinded study design was implemented to evaluate the performance of SLH formulations compared with a commercially available formulation in 12 healthy male participants after oral administration under fasting conditions. SLH formulations enhanced the bioavailability of SIM up to 1.6-fold and more importantly the active simvastatin acid (SIMA), 3.5-fold when compared with an equivalent dose of commercial formulation. The results demonstrate that the porous nanostructure of SLH impact systemic SIM and SIMA concentrations and may serve as a novel approach to enhance the bioavailability of specifically the parent or metabolite. No significant difference was observed in exposure when SLH formulations were administered at 10 mg in comparison with 20 mg of the commercial formulation, suggesting the potential for dose reduction. The study indicated that SLH formulations were safe and well-tolerated when administered to healthy males, confirming the commercial potential of SLH to enhance the bioavailability of poorly water-soluble drugs. Graphical abstract.

Exploring impact of supersaturated lipid-based drug delivery systems of celecoxib on in vitro permeation across PermeapadⓇ membrane and in vivo absorption

Supersaturated lipid-based drug delivery systems have recently been investigated for oral administration for a variety of lipophilic drugs and have shown either equivalent or superior oral bioavailability compared to conventional non-supersaturated lipid-based drug delivery systems. The aim of the present work was to explore supersaturated versus non-supersaturated lipid-based systems at equivalent lipid doses, on in vivo bioavailability in rats and on in vitro permeation across a biomimetic Permeapad^Ⓡ membrane to establish a potential in vivo - in vitro correlation. A secondary objective was to investigate the influence of lipid composition on in vitro and in vivo performance of lipid systems. Results obtained indicated that increasing the celecoxib load in the lipid-based formulations by thermally-induced supersaturation resulted in increased bioavailability for medium and long chain mono-/di-glycerides systems relative to their non-supersaturated (i.e. 85%) reference formulations, albeit only significant for the medium chain systems. Long chain systems displayed higher celecoxib bioavailability than equivalent medium chain systems, both at supersaturated and non-supersaturated drug loads. In vitro passive permeation of celecoxib was studied using both steady-state and dynamic conditions and correlated well with in vivo pharmacokinetic results with respect to compositional effects. In contrast, permeation studies indicated that flux and percentage permeated of supersaturated systems, either at steady-state or under dynamic conditions, decreased or were unchanged relative to non-supersaturated systems. This study has shown that by using two cell-free Permeapad^Ⓡ permeation models coupled with rat-adapted gastro-intestinal conditions, bio-predictive in vitro tools can be developed to be reflective of in vivo scenarios. With further optimization, such models could be successfully used in pharmaceutical industry settings to rapidly screen various prototype formulations prior to animal studies.

Supersaturated Lipid-Based Formulations to Enhance the Oral Bioavailability of Venetoclax

Increasing numbers of beyond Rule-of-Five drugs are emerging from discovery pipelines, generating a need for bio-enabling formulation approaches, such as lipid-based formulations (LBF), to ensure maximal in vivo exposure. However, many drug candidates display insufficient lipid solubility, leading to dose-loading limitations in LBFs. The aim of this study was to explore the potential of supersaturated LBFs (sLBF) for the beyond Rule-of-Five drug venetoclax. Temperature-induced sLBFs of venetoclax were obtained in olive oil, Captex^® 1000, Peceol^® and Capmul MCM^®, respectively. A Peceol^®-based sLBF displayed the highest drug loading and was therefore evaluated further. In vitro lipolysis demonstrated that the Peceol^®-based sLBF was able to generate higher venetoclax concentrations in the aqueous phase compared to a Peceol^®-based suspension and an aqueous suspension. A subsequent bioavailability study in pigs demonstrated for sLBF a 3.8-fold and 2.1-fold higher bioavailability compared to the drug powder and Peceol^®-based suspension, respectively. In conclusion, sLBF is a promising bio-enabling formulation approach to enhance in vivo exposure of beyond Rule-of-Five drugs, such as venetoclax. The in vitro lipolysis results correctly predicted a higher exposure of the sLBF in vivo. The findings of this study are of particular relevance to pre-clinical drug development, where maximum exposure is required.

Chase Dosing of Lipid Formulations to Enhance Oral Bioavailability of Nilotinib in Rats

PURPOSE

Lipid-based formulations (LBF) have shown oral bioavailability enhancement of lipophilic drugs, but not necessarily in the case of hydrophobic drugs. This study explored the potential of lipid vehicles to improve the bioavailability of the hydrophobic drug nilotinib comparing a chase dosing approach and lipid suspensions.

METHODS

Nilotinib in vivo bioavailability in rats was determined after administering an aqueous suspension chase dosed with blank olive oil, Captex 1000, Peceol or Capmul MCM, respectively. Absolute bioavailability was determined (relative to an intravenous formulation). Pharmacokinetic parameters were compared to lipid suspensions.

RESULTS

Compared to the lipid suspensions, the chase dosed lipids showed a 2- to 7-fold higher bioavailability. Both long chain chase dosed excipients also significantly increased the bioavailability up to 2-fold compared to the aqueous suspension. Deconvolution of the pharmacokinetic data indicated that chase dosing of nilotinib resulted in prolonged absorption compared to the aqueous suspension.

CONCLUSION

Chase dosed LBF enhanced the in vivo bioavailability of nilotinib. Long chain lipids showed superior performance compared to medium chain lipids. Chase dosing appeared to prolong the absorption phase of the drug. Therefore, chase dosing of LBF is favourable compared to lipid suspensions for 'brick dust' molecules such as nilotinib. Graphical Abstract The potential of bio-enabling lipid vehicles, administered via chase dosing and lipid suspensions, has been evaluated as an approach to enhance oral bioavailability of nilotinib.

Nanotechnology: A Promising Approach for Delivery of Neuroprotective Drugs

Central nervous system (CNS) disorders especially neurodegenerative disorders are the major challenge for public health and demand the great attention of researchers to protect people against them. In past few decades, different treatment strategies have been adopted, but their therapeutic efficacy are not enough and have only shown partial mitigation of symptoms. Blood-brain barrier (BBB) and blood-cerebrospinal fluid barrier (BSCFB) guard the CNS from harmful substances and pose as the major challenges in delivering drugs into CNS for treatment of CNS complications such as Alzheimer’s disease (AD), Parkinson’s disease (PD), Huntington’s disease (HD), stroke, epilepsy, brain tumors, multiple sclerosis (MS), and encephalitis, etc. Nanotechnology has come out as an exciting and promising new platform of treating neurological disorders and has shown great potential to overcome problems related to the conventional treatment approaches. Molecules can be nanoengineered to carry out multiple specific functions such as to cross the BBB, target specific cell or signaling pathway, respond to endogenous stimuli, and act as a vehicle for gene delivery, support nerve regeneration and cell survival. In present review, the role of nanocarrier systems such as liposomes, micelles, solid lipid nanoparticles (SLNPs), dendrimers, and nanoemulsions for delivery of various neurotherapeutic agents has been discussed, besides this, their mechanism of action, and nanoformulation of different neuroprotective agents like curcumin, edaravone, nerve growth factors in CNS disorders like Alzheimer’s, Parkinsonism, epilepsy, stroke, and brain tumors has been reviewed.

Development of a Self-Emulsifying Drug Delivery System for Optimized Topical Delivery of Clofazimine

A quality-by-design and characterization approach was followed to ensure development of self-emulsifying drug delivery systems (SEDDSs) destined for topical delivery of the highly lipophilic clofazimine. Solubility and water-titration experiments identified spontaneous emulsification capacity of different excipient combinations and clofazimine. After identifying self-emulsification regions, check-point formulations were selected within the self-emulsification region by considering characteristics required to achieve optimized topical drug delivery. Check-point formulations, able to withstand phase separation after 24 h at an ambient temperature, were subjected to characterization studies. Experiments involved droplet size evaluation; size distribution; zeta-potential; self-emulsification time and efficacy; viscosity and pH measurement; cloud point assessment; and thermodynamic stability studies. SEDDSs with favorable properties, i.e., topical drug delivery, were subjected to dermal diffusion studies. Successful in vitro topical clofazimine delivery was observed. Olive oil facilitated the highest topical delivery of clofazimine probably due to increased oleic acid levels that enhanced stratum corneum lipid disruption, followed by improved dermal clofazimine delivery. Finally, isothermal microcalometric experiments studied the compatibility of excipients. Potential interactions were depicted between argan oil and clofazimine as well as between Span®60 and argan-, macadamia- and olive oil, respectively. However, despite some mundane incompatibilities, successful development of topical SEDDSs achieved enhanced topical clofazimine delivery.

Enhancement of abiraterone acetate oral bioavailability by supersaturated-silica lipid hybrids

Abiraterone acetate (AbA) has an oral bioavailability of <10% due to its poor water solubility. Here we investigate the performance of silica-lipid hybrids (SLH) and supersaturated SLH (super-SLH) in improving oral bioavailability of AbA. Specifically, we investigate the influence of lipid type and AbA saturation level of the equilibrium solubility in the lipid (S_eq), and explore in vitro-in vivo correlation (IVIVC). An oral pharmacokinetic study was conducted in fasted Sprague-Dawley rats. Suspensions of the formulations were administered via oral gavage at an AbA dose of 25 mg/kg. Plasma samples were collected and analyzed for drug content. SLH with a saturation level of 90% S_eq enhanced the oral bioavailability of unformulated AbA by 31-fold, and super-SLH with saturation levels of 150, 200 and 250% S_eq, enhanced the bioavailability by 11, 10 and 7-fold, respectively. In comparison with the commercial product Zytiga, SLH (90% S_eq) increased the oral bioavailability 1.43-fold whereas super-SLH showed no improvement. A reasonable IVIVC existed between the performance of unformulated AbA, SLH and super-SLH, in the in vitro lipolysis and in vivo oral pharmacokinetic studies. SLH and super-SLH significantly enhanced the oral bioavailability of AbA. Additionally, supersaturation of SLH improved drug loading but did not correlate with enhanced AbA bioavailability.

Enhancing the oral bioavailability of simvastatin with silica-lipid hybrid particles: The effect of supersaturation and silica geometry

Silica-lipid hybrid (SLH) microparticles are a solidified lipid-based drug delivery system under investigation for their aptitude to enhance the oral bioavailability of poorly water-soluble drugs. The cholesterol-lowering agent, simvastatin (SIM), is poorly water-soluble and undergoes extensive first pass metabolism, resulting in a low oral bioavailability of approximately 5%. Hence, the current pre-clinical studies investigated the application of SLH technology to SIM with a supersaturation approach, aiming to enhance bioavailability and drug loading capacity. Additionally, the effect of silica was explored by evaluating the performance of SLH fabricated with silica of different particle geometries. SLH microparticles with supersaturated SIM loading levels ranging from 100% to 400% above the equilibrium solubility were successfully fabricated using either Aerosil® 300 or Syloid® 244 silica. All SLH formulations existed as white free-flowing powders, consisting of spherical porous microparticles for Aerosil® 300, and aggregated irregular microparticles for Syloid® 244. During in vitro dissolution in pH 7.0 media, the SLH formulations performed up to 4.4-fold greater than pure SIM powder. Furthermore, in vivo oral pharmacokinetics in male Sprague-Dawley rats revealed that the SLH formulations enhanced the oral bioavailability of SIM up to 6.1-fold and 2.9-fold, in comparison to pure SIM powder and a commercially available formulation (Simvastatin Sandoz®), respectively. The greatest in vivo performance enhancement was observed for the SLH formulation manufactured with Syloid® 244 silica with a supersaturation level of 200%. SLH technology demonstrated to be a successful formulation strategy to significantly improve the oral bioavailability of SIM in rodents and therefore, has a strong potential to also improve the oral bioavailability of SIM in humans.

Current Status of Supersaturable Self-Emulsifying Drug Delivery Systems

Self-emulsifying drug delivery systems (SEDDSs) are a vital strategy to enhance the bioavailability (BA) of formulations of poorly water-soluble compounds. However, these formulations have certain limitations, including in vivo drug precipitation, poor in vitro in vivo correlation due to a lack of predictive in vitro tests, issues in handling of liquid formulation, and physico-chemical instability of drug and/or vehicle components. To overcome these limitations, which restrict the potential usage of such systems, the supersaturable SEDDSs (su-SEDDSs) have gained attention based on the fact that the inclusion of precipitation inhibitors (PIs) within SEDDSs helps maintain drug supersaturation after dispersion and digestion in the gastrointestinal tract. This improves the BA of drugs and reduces the variability of exposure. In addition, the formulation of solid su-SEDDSs has helped to overcome disadvantages of liquid or capsule dosage form. This review article discusses, in detail, the current status of su-SEDDSs that overcome the limitations of conventional SEDDSs. It discusses the definition and range of su-SEDDSs, the principle mechanisms underlying precipitation inhibition and enhanced in vivo absorption, drug application cases, biorelevance in vitro digestion models, and the development of liquid su-SEDDSs to solid dosage forms. This review also describes the effects of various physiological factors and the potential interactions between PIs and lipid, lipase or lipid digested products on the in vivo performance of su-SEDDSs. In particular, several considerations relating to the properties of PIs are discussed from various perspectives.

Oral formulation strategies to improve the bioavailability and mitigate the food effect of abiraterone acetate

Abiraterone acetate, marketed as Zytiga®, is an antiandrogen medication used in the treatment of prostate cancer. Abiraterone acetate is a BCS Class IV compound associated with several oral delivery challenges. Its low solubility and high lipophilicity lead to poor oral bioavailability (<10%) and a dramatic positive food effect (5-10-fold). Hence, a large dose of abiraterone acetate (1000 mg per day) is prescribed to patients who must fast for at least 1 h before and 2 h after administration. The recent expiry of Zytiga®s' patent has led to the emergence of publications describing improved oral formulation strategies for abiraterone acetate. This review aims to discuss the characteristics of abiraterone acetate that lead to its unfavorable oral delivery, examine the oral formulation strategies that have been applied, and to describe potential alternative oral formulation strategies that have been used for other BCS Class IV drugs, to determine the most valuable strategies to develop novel and improved alternatives to the current commercial product. Specific emphasis of this review is placed on enabling oral formulation strategies that can improve solubilization and bioavailability, reduce the clinical dose and remove the pharmaceutical food effect to ultimately provide prostate cancer patients with a more efficient formulation with greater patient compliance.

Improving the drug load and in vitro performance of supersaturated self-nanoemulsifying drug delivery systems (super-SNEDDS) using polymeric precipitation inhibitors

In this study, the influence of the polymeric precipitation inhibitor (PPI) PVP/VA 64 (polyvinylpyrrolidone-co-vinyl acetate) on the physical stability and in vitro performance of supersaturated self-nanoemulsifying drug delivery systems (super-SNEDDS) containing the model drug simvastatin (SIM) was investigated. A heating-cooling cycle was employed to dissolve (i) the drug in the SNEDDS preconcentrate, generating super-SNEDDS, or (ii) the drug and PPI generating PPI super-SNEDDS, both containing drug loads of 200% and 250% (with regard to the equilibrium solubility of SIM in the blank SNEDDS). PPI super-SNEDDS were prepared at PPI concentrations of 1%, 10% and 20% (w/w), respectively. The formulations were characterized using polarized light microscopy, dynamic light scattering, rheological profiling and dynamic in vitro lipolysis. The physical stability of PPI super-SNEDDS correlated with an increase in viscosity due to the additionally dissolved PVP/VA 64. PPI super-SNEDDS with drug loads of 200% and 250% containing 20% (w/w) PPI showed no drug recrystallization after more than 6 months of storage at room temperature, whereas PPI-free super-SNEDDS (250% drug load) recrystallized within two hours after equilibration to room temperature. All formulations formed nanosized droplets after emulsification in Milli-Q water. The droplet size was not affected by the PPI, but increased slightly with increasing drug load (z-average of 47.3 ± 0.4 nm for SNEDDS with 200% drug load and 55.6 ± 1.3 nm for SNEDDS with 250% drug load). PPI super-SNEDDS with a drug load of 200% containing 20% (w/w) PVP/VA 64 showed an improved performance during dynamic in vitro lipolysis, maintaining a 2.5-fold higher degree of supersaturation after 15 min of digestion compared to PPI-free super-SNEDDS of the same drug load. In conclusion, the study demonstrated the feasibility of stabilizing higher drug loads and improving the in vitro performance of super-SNEDDS by incorporating PVP/VA 64 into the preconcentrate.

Mathematical Modeling of Release Kinetics from Supramolecular Drug Delivery Systems

Embedding of active substances in supramolecular systems has as the main goal to ensure the controlled release of the active ingredients. Whatever the final architecture or entrapment mechanism, modeling of release is challenging due to the moving boundary conditions and complex initial conditions. Despite huge diversity of formulations, diffusion phenomena are involved in practically all release processes. The approach in this paper starts, therefore, from mathematical methods for solving the diffusion equation in initial and boundary conditions, which are further connected with phenomenological conditions, simplified and idealized in order to lead to problems which can be analytically solved. Consequently, the release models are classified starting from the geometry of diffusion domain, initial conditions, and conditions on frontiers. Taking into account that practically all solutions of the models use the separation of variables method and integral transformation method, two specific applications of these methods are included. This paper suggests that "good modeling practice" of release kinetics consists essentially of identifying the most appropriate mathematical conditions corresponding to implied physicochemical phenomena. However, in most of the cases, models can be written but analytical solutions for these models cannot be obtained. Consequently, empiric models remain the first choice, and they receive an important place in the review.

Solidification to improve the biopharmaceutical performance of SEDDS: Opportunities and challenges

Self-emulsifying drug delivery systems (SEDDS) offer potential for overcoming the inherent slow dissolution and poor oral absorption of hydrophobic drugs by retaining them in a solubilised state during gastrointestinal transit. However, the promising biopharmaceutical benefits of liquid lipid formulations has not translated into widespread commercial success, due to their susceptibility to long term storage and in vivo precipitation issues. One strategy that has emerged to overcome such limitations, is to combine the solubilisation and dissolution enhancing properties of lipids with the stabilising effects of solid carrier materials. The development of intelligent hybrid drug formulations has presented new opportunities to harness the potential of emulsified lipids in optimising oral bioavailability for lipophilic therapeutics. Specific emphasis of this review is placed on the impact of solidification approaches and excipients on the biopharmaceutical performance of self-emulsifying lipids, with findings highlighting the key design considerations that should be implemented when developing hybrid lipid-based formulations.

In vitro digestion models to evaluate lipid based drug delivery systems; present status and current trends

During the past two decades, a range of in vitro models simulating the digestion processes occurring in the stomach and small intestine have been developed to characterize lipid based drug delivery systems (LbDDSs). This review describes the presently existing range of in vitro digestion models and their use in the field of oral drug delivery. The models are evaluated in terms of their suitability to assess LbDDSs, and their ability to produce in vitro - in vivo correlations (IVIVCs). While the pH-stat lipolysis model is by far the most commonly utilized in vitro digestion model in relation to characterizing LbDDSs, a series of recent studies have shown a lack of IVIVCs limiting its future use. Presently, no single in vitro digestion model exists which is able to predict the in vivo performance of various LbDDSs. However, recent research has shown the potential of combined digestion-permeation models as well as species specific digestion models.

Bridging the gaps between academic research and industrial product developments of lipid-based formulations

Lipid-based formulations, including self-emulsifying drug delivery systems (SEDDS), are an interesting formulation technology that enables the clinical use of compounds for which a low aqueous solubility may be a limitation. From an academic perspective, the technology is interesting on several levels: what drives solubility, what determines bioperformance, what is the potential for solidification etc. From an industrial perspective, >35 lipid-based formulations are available and there is an unknown number of projects in the pipeline. Hence, while there is scientific interest from both academic and industrial perspectives, the agendas/needs in the two settings are different. From an industrial perspective, risks are associated with uncertainty; hence the more that is known about a technology the better - knowledge that in principle can be generated in both the academia and industry. This focuses on the development of lipid-based formulations and the knowledge gaps that could be investigated -with the hope that all stakeholders in the field of lipid-based formulations, including academia, industry, CRO's, lipid excipient manufacturers etc., would share their insight, so that this technology can be even further developed. Some of the gaps discussed include the selection of compounds suited for lipid-based formulations, which potential modifications that could be investigated, e.g., lipophilic salts, what is a relevant definition of accelerated stability studies, how best to construct an industrial development program of a lipid-based formulation, etc.

Self-emulsifying drug delivery system: Mucus permeation and innovative quantification technologies

Mucus is a dynamic barrier which covers and protects the underlying mucosal epithelial membrane against bacteria and foreign particles. This protection mechanism extends to include therapeutic macromolecules and nanoparticles (NPs) through trapping of these particles. Mucus is not only a physical barrier that limiting particles movements based on their sizes but it selectively binds with particles through both hydrophilic and lipophilic interactions. Therefore, nano-carriers for mucosal delivery should be designed to eliminate entrapment by the mucus barrier. For this reason, different strategies have been approached for both solid nano-carriers and liquid core nano-carriers to synthesise muco-diffusive nano-carrier. Among these nano-strategies, Self-Emulsifying Drug Delivery System (SEDDS) was recognised as very promising nano-carrier for mucus delivery. The system was introduced to enhance the dissolution and bioavailability of orally administered insoluble drugs. SEDDS has shown high stability against intestinal enzymatic activity and more importantly, relatively rapid permeation characteristics across mucus barrier. The high diffusivity of SEDDS has been tested using various in vitro measurement techniques including both bulk and individual measurement of droplets diffusion within mucus. The selection and processing of an optimum in vitro technique is of great importance to avoid misinterpretation of the diffusivity of SEDDS through mucus barrier. In conclusion, SEDDS is a system with high capacity to diffuse through intestinal mucus even though this system has not been studied to the same extent as solid nano-carriers.

New Insights into Using Lipid Based Suspensions for 'Brick Dust' Molecules: Case Study of Nilotinib

PURPOSE

Lipid suspensions have been shown to be a suitable bio-enabling formulation approach for highly lipophilic or 'grease ball' drug molecules, but studies on 'brick dust' drugs are lacking. This study explored the utility of lipid suspensions for enhancing oral bioavailability of the rather hydrophobic drug nilotinib in vivo in rats.

METHODS

Four lipid suspensions were developed containing long chain triglycerides, medium chain triglyceride, long chain monoglycerides and medium chain monoglycerides and in vivo bioavailability was compared to an aqueous suspension. Additionally, in vitro lipolysis and wettability tests were conducted.

RESULTS

Nilotinib lipid suspensions did not show a bioavailability increase compared to an aqueous suspension. The bioavailability was lower for triglyceride suspensions, relative to both monoglyceride and an aqueous suspension. The long chain monoglyceride displayed a significantly higher bioavailability relative to triglycerides. In vitro lipolysis results suggested entrapment of nilotinib crystals within poorly dispersible triglycerides, leading to slower nilotinib release and absorption. This was further supported by higher wettability of nilotinib by lipids.

CONCLUSION

Monoglycerides improved oral bioavailability of nilotinib in rats, relative to triglycerides. For 'brick dust' drugs formulated as lipid suspensions, poorly dispersible formulations may delay the release of drug crystals from the formulation leading to reduced absorption. Graphical Abstract An aqueous and four lipid suspensions have been evaluated in in vitro and in vivo to gain insights into the potential benefits and limitations of lipid suspensions.

Physical Characterization of Halofantrine-Encapsulated Fat Nanoemulsions

We report the colloidal characterization of halofantrine (Hf)-laden soybean oil fat emulsions. Hf increased the zeta potential, at all pH values, of the fat emulsions. Concomitant with this, the isoelectric point (i.e.p.) of the emulsion increased to higher pH values. The emulsion was destabilized by a small amount of Hf; interestingly, however, this was ameliorated by increasing the amount of Hf. The particle size and polydispersity of the fat emulsion reflected this with a small Hf concentration resulting in a significant increase in both particle size and polydispersity, but less so as the Hf concentration was increased. Emulsions lost stability as the pH approached the i.e.p. and this effect was greatest for the small Hf concentration emulsions. Cryogenic transmission electron microscopy showed the presence of beading or string-like behavior leading to gross distortions of the spherical shape for highly unstable emulsions. We conclude that to maintain good stability for Hf-laden soybean oil emulsions, the pH of the emulsion should be kept away from its i.e.p, and also that the drug concentration should be maintained at a relatively high value.