50years of oral lipid-based formulations: Provenance, progress and future perspectives

Computational and Experimental Models of Type III Lipid-Based Formulations of Loratadine Containing Complex Nonionic Surfactants

Type III lipid-based formulations (LBFs) combine poorly water-soluble drugs with oils, surfactants, and cosolvents to deliver the drugs into the systemic circulation. However, the solubility of the drug can be influenced by the colloidal phases formed in the gastrointestinal tract as the formulation is dispersed and makes contact with bile and other materials present within the GI tract. Thus, an understanding of the phase behavior of LBFs in the gut is critical for designing efficient LBFs. Molecular dynamics (MD) simulation is a powerful tool for the study of colloidal systems. In this study, we modeled the internal structures of five type III LBFs of loratadine containing poly(ethylene oxide) nonionic surfactants polysorbate 80 and polyoxyl hydrogenated castor oil (Kolliphor RH40) using long-timescale MD simulations (0.4-1.7 μs). We also conducted experimental investigations (dilution of formulations with water) including commercial Claritin liquid softgel capsules. The simulations show that LBFs form continuous phase, water-swollen reverse micelles, and bicontinuous and phase-separated systems at different dilutions, which correlate with the experimental observations. This study supports the use of MD simulation as a predictive tool to determine the fate of LBFs composed of medium-chain lipids, polyethylene oxide surfactants, and polymers.

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.

Lipid-based formulations to increase cannabidiol bioavailability: In vitro digestion tests, pre-clinical assessment and clinical trial

Herein, medium-chain triglycerides (MCT), glyceryl monolinoleate (GML), and a self-emulsifying drug delivery system (SEDDS) for cannabidiol (CBD) delivery were compared using in vitro and in vivo (mouse and human) studies. In vitro digestion tests showed that SEDDS yielded the highest CBD recovery in the aqueous phase (86 ± 2%), followed by GML (13 ± 2%) and MCT (5.6% ± 0.8%). In vivo tests (mouse) revealed that SEDDS promoted the highest CBD exposure, exhibiting an area under the plasma concentration-time curve (AUC_0-6h) 1.48 times greater than GML and 3.97 times greater than that of the MCT formulation. A single-dose, open-label, crossover study performed in 11 volunteers showed that SEDDS increased CBD AUC_0-12h by 1.12 and 1.48 times in relation to GML and MCT, respectively. The in vitro-in vivo correlation was r² 0.75 for mice and r² 0.66 for humans. The AUC correlation between mice and humans was 0.98. Collectively, these results indicate that the lipid profile substantially influences CBD delivery and highlights the potential of the SEDDS and GML formulations as candidate solutions for increasing CBD AUC and bioavailability.

Formulation and In Vivo Evaluation of a Solid Self-Emulsifying Drug Delivery System Using Oily Liquid Tocotrienols as Model Active Substance

Self-emulsifying drug delivery systems (SEDDS) can improve the oral bioavailability of poorly water-soluble drugs. Solid self-emulsifying drug delivery systems (s-SEDDS) offer several advantages including improved drug stability, ease of administration, and production. Most compounds employed in developing s-SEDDS are solid in nature, with a high amount of surfactants added. The aim of this study was to develop an s-SEDDS using a tocotrienol-rich fraction (TRF) as the model liquid active substance via a simple adsorption method. The solid formulation was developed using magnesium aluminosilicate as the carrier with 70% TRF and 30% surfactants (poloxamer and Labrasol^®). The formulation showed good self-emulsification efficiency with stable emulsion formed, excellent powder flowability, and small emulsion droplet size of 210–277 nm. The s-SEDDS with combined surfactants (poloxamer and Labrasol^®) showed a faster absorption rate compared to preparations with only a single surfactant and enhanced oral bioavailability (3.4–3.8 times higher) compared to the non-self-emulsifying oily preparation when administered at a fasted state in rats. In conclusion, an s-SEDDS containing a high amount of TRF was successfully developed. It may serve as a useful alternative to a liquid product with enhanced oral bioavailability and the added advantage of being a solid dosage form.

Harnessing the potential of nanostructured formulations to mimic the food effect of lurasidone

Lurasidone is an important antipsychotic drug indicated for the treatment of schizophrenia and bipolar disorder, with an oral bioavailability of 9-19% owing to its poor aqueous solubility. Additionally, lurasidone exhibits a 2-fold positive food effect, such that patients must administer their medication with a meal, leading to significant non-compliance. The aim of this research was to evaluate the in vitro and in vivo performance of lurasidone when engineered as nanostructured systems. Specifically, a nanosuspension, nano-emulsion and silica-lipid hybrid (SLH) microparticles were formulated and the influence of composition and nanostructure on the mechanism of solubilisation was compared. Formulations were shown to enhance fasted state solubilisation levels in vitro by up to 5.9-fold, compared to pure drug. Fed- and fasted-state solubilisation profiles revealed that in contrast to the nanosuspension and nano-emulsion, lurasidone SLH mitigated the positive pharmaceutical effect of lurasidone. In vivo pharmacokinetic evaluations revealed that the nanosuspension, nano-emulsion and SLH enhanced the bioavailability of lurasidone by 3-fold, 2.4-fold and 8.8-fold, respectively, compared to pure drug after oral administration. For lurasidone, the combination of lipid-based nanostructure and porous silica nanostructure (SLH) led to optimal fasted state bioavailability which can ultimately result in enhanced treatment efficacy, easier dosing regimens and improved patient outcomes.

Lipid-based emulsion drug delivery systems - a comprehensive review

Lipid-based emulsion system - a subcategory of emulsion technology, has emerged as an enticing option to improve the solubility of the steadily rising water-insoluble candidates. Along with enhancing solubility, additional advantages such as improvement in permeability, protection against pre-systemic metabolism, ease of manufacturing, and easy to scale-up have made lipid-based emulsion technology very popular among academicians and manufacturers. The present article provides a comprehensive review regarding various critical properties of lipid-based emulsion systems, such as microemulsion, nanoemulsion, SMEDDS (self microemulsifying drug delivery system), and SNEDDS (self nanoemulsifying drug delivery system). The present article also explains in detail the similarities and differences between them, the stabilization mechanism, methods of preparation, excipients used to prepare them, and evaluation techniques. Subtle differences between nearly related terminologies such as microemulsion and nanoemulsion, SMEDDS, and SNEDDS are also explained in detail to clarify the basic differences. The present article also gives in-depth information regarding the chemical structure of various lipidic excipients, various possible chemical modifications to modify their inherent properties, and their regulatory status for rational selection.

Formulation strategies to improve the efficacy of intestinal permeation enhancers. Adv Drug Deliv Rev 2021;177:113925. [PMID: 34418495 DOI: 10.1016/j.addr.2021.113925]

The use of chemical permeation enhancers (PEs) is the most widely tested approach to improve oral absorption of low permeability active agents, as represented by peptides. Several hundred PEs increase intestinal permeability in preclinical bioassays, yet few have progressed to clinical testing and, of those, only incremental increases in oral bioavailability (BA) have been observed. Still, average BA values of ~1% were sufficient for two recent FDA approvals of semaglutide and octreotide oral formulations. PEs are typically screened in static in vitro and ex-vivo models where co-presentation of active agent and PE in high concentrations allows the PE to alter barrier integrity with sufficient contact time to promote flux across the intestinal epithelium. The capacity to maintain high concentrations of co-presented agents at the epithelium is not reached by standard oral dosage forms in the upper GI tract in vivo due to dilution, interference from luminal components, fast intestinal transit, and possible absorption of the PE per se. The PE-based formulations that have been assessed in clinical trials in either immediate-release or enteric-coated solid dosage forms produce low and variable oral BA due to these uncontrollable physiological factors. For PEs to appreciably increase intestinal permeability from oral dosage forms in vivo, strategies must facilitate co-presentation of PE and active agent at the epithelium for a sustained period at the required concentrations. Focusing on peptides as examples of a macromolecule class, we review physiological impediments to optimal luminal presentation, discuss the efficacy of current PE-based oral dosage forms, and suggest strategies that might be used to improve them.

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.

Comparison of Cellular Monolayers and an Artificial Membrane as Absorptive Membranes in the in vitro Lipolysis-permeation Assay

Permeation across Caco-2 cells in lipolysis-permeation setups can predict the rank order of in vivo drug exposure obtained with lipid-based formulations (LBFs). However, Caco-2 cells require a long differentiation period and do not capture all characteristics of the human small intestine. We therefore evaluated two in vitro assays with artificial lecithin-in-dodecane (LiDo) membranes and MDCK cells as absorptive membranes in the lipolysis-permeation setup. Fenofibrate-loaded LBFs were used and the results from the two assays compared to literature plasma concentrations in landrace pigs administered orally with the same formulations. Aqueous drug concentrations, supersaturation, and precipitation were determined in the digestion chamber and drug permeation in the receiver chamber. Auxiliary in vitro parameters were assessed, such as permeation of the taurocholate, present in the simulated intestinal fluid used in the assay, and size of colloidal structures in the digestion medium over time. The LiDo membrane gave a similar drug distribution as the Caco-2 cells and accurately reproduced the equivalent rank-order of fenofibrate exposure in plasma. Permeation of fenofibrate across MDCK monolayers did not, however, reflect the in vivo exposure rankings. Taurocholate flux was negligible through either membrane. This process was therefore not considered to significantly affect the in vitro distribution of fenofibrate. We conclude that the artificial LiDo membrane is a promising tool for lipolysis-permeation assays to evaluate LBF performance.

From influenza to COVID-19: Lipid nanoparticle mRNA vaccines at the frontiers of infectious diseases

Vaccination represents the best line of defense against infectious diseases and is crucial in curtailing pandemic spread of emerging pathogens to which a population has limited immunity. In recent years, mRNA vaccines have been proposed as the new frontier in vaccination, owing to their facile and rapid development while providing a safer alternative to traditional vaccine technologies such as live or attenuated viruses. Recent breakthroughs in mRNA vaccination have been through formulation with lipid nanoparticles (LNPs), which provide both protection and enhanced delivery of mRNA vaccines in vivo. In this review, current paradigms and state-of-the-art in mRNA-LNP vaccine development are explored through first highlighting advantages posed by mRNA vaccines, establishing LNPs as a biocompatible delivery system, and finally exploring the use of mRNA-LNP vaccines in vivo against infectious disease towards translation to the clinic. Furthermore, we highlight the progress of mRNA-LNP vaccine candidates against COVID-19 currently in clinical trials, with the current status and approval timelines, before discussing their future outlook and challenges that need to be overcome towards establishing mRNA-LNPs as next-generation vaccines. STATEMENT OF SIGNIFICANCE: With the recent success of mRNA vaccines developed by Moderna and BioNTech/Pfizer against COVID-19, mRNA technology and lipid nanoparticles (LNP) have never received more attention. This manuscript timely reviews the most advanced mRNA-LNP vaccines that have just been approved for emergency use and are in clinical trials, with a focus on the remarkable development of several COVID-19 vaccines, faster than any other vaccine in history. We aim to give a comprehensive introduction of mRNA and LNP technology to the field of biomaterials science and increase accessibility to readers with a new interest in mRNA-LNP vaccines. We also highlight current limitations and future outlook of the mRNA vaccine technology that need further efforts of biomaterials scientists to address.

Investigation of Self-Emulsifying Drug-Delivery System Interaction with a Biomimetic Membrane under Conditions Relevant to the Small Intestine

Self-emulsifying drug-delivery systems (SEDDS) have been extensively shown to increase oral absorption of solvation-limited compounds. However, there has been little clinical and commercial use of these formulations, in large part because the demonstrated advantages of SEDDS have been outweighed by our inability to precisely predict drug absorption from SEDDS using current in vitro assays. To overcome this limitation and increase the biological relevancy of in vitro assays, an absorption function can be incorporated using biomimetic membranes. However, the effects that SEDDS have on the integrity of a biomimetic membrane are not known. In this study, a quartz crystal microbalance with dissipation monitoring and total internal reflection fluorescence microscopy were employed as complementary methods to in vitro lipolysis-permeation assays to characterize the interaction of various actively digested SEDDS with a liquescent artificial membrane comprising lecithin in dodecane (LiDo). Observations from surface analysis showed that interactions between the digesting SEDDS and LiDo membrane coincided with inflection points in the digestion profiles. Importantly, no indications of membrane damage could be observed, which was supported by flux profiles of the lipophilic model drug felodipine (FEL) and impermeable marker Lucifer yellow on the basal side of the membrane. There was a correlation between the digestion kinetics of the SEDDS and the flux of FEL, but no clear correlation between solubilization and absorption profiles. Membrane interactions were dependent on the composition of lipids within each SEDDS, with the more digestible lipids leading to more pronounced interactions, but in all cases, the integrity of the membrane was maintained. These insights demonstrate that LiDo membranes are compatible with in vitro lipolysis assays for improving predictions of drug absorption from lipid-based formulations.

Solid self emulsifying drug delivery system: Superior mode for oral delivery of hydrophobic cargos

A significant proportion of recently approved drug molecules possess poor aqueous solubility which further restrains their desired bioavailability. Poor aqueous solubility of these drugs poses significant hurdles in development of novel drug delivery systems and achieving target response. Self-emulsifying drug delivery systems (SEDDS) emerged as an insightful approach for delivering highly hydrophobic entities to enhance their bioavailability. Conventional SEDDS were developed in a liquid form which owned numerous shortcomings like low stability and drug loading efficiency, fewer choices of dosage forms and irreversible precipitation of drug or excipients. To address these curbs solid-SEDDS (S-SEDDS) was introduced as an efficient strategy that combined advantages of solid dosage forms such as increased stability, portability and patient compliance along with substantial improvement in the bioavailability. S-SEDDS are isotropic mixtures of oil, surfactant, solvent and co-solvents generated by solidification of liquid or semisolid self-emulsifying ingredients onto powders. The present review highlights components of S-SEDDS, their peculiarities to be considered while designing solid dosage forms and various methods of fabrication. Lastly, key challenges faced during development, applications and future directions for the research in this area are thoroughly summarized.

Maximizing the Oral Bioavailability of Poorly Water-Soluble Drugs Using Novel Oil-Like Materials in Lipid-Based Formulations

Lipid-based formulations, such as self-microemulsifying drug-delivery systems (SMEDDSs), are promising tools for the oral delivery of poorly water-soluble drugs. However, failure to maintain adequate aqueous solubility after coming into contact with gastrointestinal fluids is a major drawback. In this study, we examined the use of a novel cinnamic acid-derived oil-like material (CAOM) that binds drugs with a high affinity through π-π stacking and hydrophobic interactions, as an oil core in a SMEDDS for the oral delivery of fenofibrate in rats. The use of the CAOM in the SMEDDS resulted in an unprecedented enhancement in fenofibrate bioavailability, which exceeded the bioavailability values obtained using SMEDDSs based on corn oil, a conventional triglyceride oil, or Labrasol, an enhancer of intestinal permeation. Further characterization revealed that the CAOM SMEDDS does not alter the intestinal permeability and has no inhibitory activity on P-glycoprotein-mediated drug efflux. The results reported herein demonstrate the strong potential of CAOM formulations as new solubilizers for the efficient and safe oral delivery of drugs that have limited water solubility.

In vitro and in vivo correlation for lipid-based formulations: Current status and future perspectives

Lipid-based formulations (LBFs) have demonstrated a great potential in enhancing the oral absorption of poorly water-soluble drugs. However, construction of in vitro and in vivo correlations (IVIVCs) for LBFs is quite challenging, owing to a complex in vivo processing of these formulations. In this paper, we start with a brief introduction on the gastrointestinal digestion of lipid/LBFs and its relation to enhanced oral drug absorption; based on the concept of IVIVCs, the current status of in vitro models to establish IVIVCs for LBFs is reviewed, while future perspectives in this field are discussed. In vitro tests, which facilitate the understanding and prediction of the in vivo performance of solid dosage forms, frequently fail to mimic the in vivo processing of LBFs, leading to inconsistent results. In vitro digestion models, which more closely simulate gastrointestinal physiology, are a more promising option. Despite some successes in IVIVC modeling, the accuracy and consistency of these models are yet to be validated, particularly for human data. A reliable IVIVC model can not only reduce the risk, time, and cost of formulation development but can also contribute to the formulation design and optimization, thus promoting the clinical translation of LBFs.

An update on oral drug delivery via intestinal lymphatic transport

Orally administered drug entities have to survive the harsh gastrointestinal environment, penetrate the enteric epithelia and circumvent hepatic metabolism before reaching the systemic circulation. Whereas the gastrointestinal stability can be well maintained by taking proper measures, hepatic metabolism presents as a formidable barrier to drugs suffering from first-pass metabolism. The pharmaceutical academia and industries are seeking alternative pathways for drug transport to circumvent problems associated with the portal pathway. Intestinal lymphatic transport is emerging as a promising pathway to this end. In this review, we intend to provide an updated overview on the rationale, strategies, factors and applications involved in intestinal lymphatic transport. There are mainly two pathways for peroral lymphatic transport-the chylomicron and the microfold cell pathways. The underlying mechanisms are being unraveled gradually and nowadays witness increasing research input and applications.

Development of self-microemulsifying lipid-based formulations of trans-resveratrol by systematically constructing lipid-surfactant-water phase diagrams using long-chain lipids

The aim of this work was to develop self-microemulsifying lipid-based formulations of trans-resveratrol in cod liver oil, a long chain lipid, to increase its solubility, dissolution rate and oral bioavailability. Ternary phase diagrams of cod liver oil with surfactant and water as well as pseudo-ternary phase diagrams of the same by mixing cod liver oil (triglyceride) with glycerol monooleate (monoglyeride) were constructed to identify regions where microemulsions were formed. Kolliphor RH 40, Tween 80 and their 1:1-mixtures were evaluated as surfactants. No organic cosolvents were added. It was observed that cod liver oil alone did not form microemulsion with any of the surfactants used, and a 1:1 mixture of cod liver oil and glycerol monooleate was necessary to enable the formation of microemulsion. Among the surfactants, Kolliphor RH 40 provided the maximum microemulsification effect. Several formulations containing 6:4, 1:1, and 4:6 w/w ratios of lipid to surfactant using the 1:1 mixture of cod liver oil and glycerol monooleate as lipid components and Kolliphor RH 40 or its mixture with Tween 80 as surfactants were identified, and trans-resveratrol solubility in these formulations were determined. Drug concentrations used in the formulations were 80% of saturation solubility, and no organic cosolvents were used in any formulations to increase drug solubility or enable emulsification. In vitro dispersion testing in 250 mL of 0.01 N HCl (pH 2) according to the USP method 2 at 50 RPM showed that the formulations rapidly dispersed in aqueous media forming microemulsions and there was no drug precipitation.

Novel amorphous solid dispersion based on natural deep eutectic solvent for enhancing delivery of anti-tumor RA-XII by oral administration in rats

At present, oral chemotherapy showing the advantages of non-invasiveness, convenience, and high patient compliance, is gradually replacing traditional intravenous chemotherapy to treat patients with cancer. RA-XII, a unique natural cyclopeptide, exhibits various biological activities, such as anti-tumor, anti-angiogenic, and anti-metastatic activities. Designing an orally available formulation of RA-XII is of great importance in the development of clinically useful anticancer agents. However, RA-XII shows low oral bioavailability in rats due to its poor solubility and low permeability. To overcome these limitations, in this work, a natural deep eutectic solvent (NADES) was designed to efficiently deliver RA-XII by oral administration. A novel NADES composed of betaine and mandelic acid in the molar ratio of 1:1 (Bet-Man NADES) was successfully prepared based on a binary phase diagram of Bet and Man. Acute toxicity studies indicated that Bet-Man NADES was well tolerated with acceptable toxicity. In Bet-Man NADES solutions, the solubility of RA-XII was increased by up to 17.54-fold, and the diffusion and permeability of RA-XII carried out in a Franz cell was also significantly improved 10.35 times. In terms of biopharmaceutical classification this is translated into a change for RA-XII from class IV to class II systems. More importantly, Bet-Man NADES was transferred into the solid formulation by the inclusion of a polymer, and amorphous solid dispersions based on Bet-Man NADES (PVP K30/NADES/RA-XII, ASDs) were successfully prepared to improve uniformity, apparent solubility, dissolution, and cytotoxicity in vitro. Consequently, the oral bioavailability of RA-XII in NADES solutions and ASDs was enhanced by approximately 11.58 and 7.56 times compared with that of pure RA-XII in 0.5% CMCNa. Thus, it can be seen that a natural deep eutectic solvent and its modified amorphous solid dispersions are appropriate novel strategies for improving dissolution rate and bioavailability of poor soluble natural products such as RA-XII.

Structured edible lipid-based particle systems for oral drug-delivery

Oral administration is the most popular and patient-compliant route for drug delivery, though it raises great challenges due to the involvement of the gastro-intestine (GI) system and the drug bioavailability. Drug bioavailability is directly related to its ability to dissolve, transport and/or absorb through the physiological environment. A great number of drugs are characterized with low water solubility due to their hydrophobic nature, thus limiting their oral bioavailability and clinical use. Therefore, new strategies aiming to provide a protective shell through the GI system and improve drug solubility and permeability in the intestine were developed to overcome this limitation. Lipid-based systems have been proposed as good candidates for such a task owing to their hydrophobic nature which allows high drug loading, drug micellization ability during intestinal digestion due to the lipid content, and the vehicle physical protective environment. The use of edible lipids with high biocompatibility paves the bench-to-bedside translation. Four main types of structured lipid-based drug delivery systems differing in the physical state of the lipid phase have been described in the literature, namely emulsions, solid lipid nanoparticles, nanostructured lipid carriers, and oleogel-based particles. The current review provides a comprehensive overview of the different structured edible lipid-based oral delivery systems investigated up to date and emphasizes the contribution of each system component to the delivery performance, and the oral delivery path of lipids.

Investigating In Vitro and Ex Vivo Properties of Artemether/Lumefantrine Double-Fixed Dose Combination Lipid Matrix Tablets Prepared by Hot Fusion

Highly lipophilic antimalarial drugs, artemether and lumefantrine, whilst an effective fixed-dose combination treatment to lower the malarial disease burden, are therapeutically hindered by low aqueous solubility and varied bioavailability. This work investigates the plausibility of directly compressed lipid matrix tablets, their role as lipid-based formulations and their future standing as drug delivery systems. Lipid matrix tablets were manufactured from solid lipid dispersions in various lipid:drug ratios employing hot fusion—the melt mixing of highly lipophilic drugs with polymer(s). Sequential biorelevant dissolution media, multiple mathematical models and ex vivo analysis utilizing porcine tissue samples were employed to assess drug release kinetics and more accurately predict in vitro performance. Directly compressed stearic acid tablets in a 0.5:1 lipid:drug ratio were deemed optimal within investigated parameters. Biorelevant media was of immense value for artemether release analysis, with formulation SA0.5C1 (Stearic Acid:double fixed dose in a 0.5:1 ratio (i.e., Stearic acid 70 mg + Lumefantrine 120 mg + Artemether 20 mg); CombiLac^® as filler (q.s.); and 1% w/w magnesium stearate) yielding a higher percentage of artemether release (97.21%) than the commercially available product, Coartem^® (86.12%). However, dissolution media lacked the specificity to detect lumefantrine. Nonetheless, stearic acid lipid:drug ratios governed drug release mechanisms. This work demonstrates the successful utilization of lipids as pharmaceutical excipients, particularly in the formulation of lipid matrix tablets to augment the dissolution of highly lipophilic drugs, and could thus potentially improve current malarial treatment regimens.

Formation of Self-Assembled Mesophases During Lipid Digestion

Lipids play an important role in regulating bodily functions and providing a source of energy. Lipids enter the body primarily in the form of triglycerides in our diet. The gastrointestinal digestion of certain types of lipids has been shown to promote the self-assembly of lipid digestion products into highly ordered colloidal structures. The formation of these ordered colloidal structures, which often possess well-recognized liquid crystalline morphologies (or “mesophases”), is currently understood to impact the way nutrients are transported in the gut and absorbed. The formation of these liquid crystalline structures has also been of interest within the field of drug delivery, as it enables the encapsulation or solubilization of poorly water-soluble drugs in the aqueous environment of the gut enabling a means of absorption. This review summarizes the evidence for structure formation during the digestion of different lipid systems associated with foods, the techniques used to characterize them and provides areas of focus for advancing our understanding of this emerging field.

Formulation of ionic liquid APIs via spray drying processes to enable conversion into single and two-phase solid forms

Ionic liquid (IL) forms of drugs are increasingly being explored to address problems presented by poorly water-soluble drugs and solid-state stability. However, before ILs of active pharmaceutical ingredients (APIs) can be routinely incorporated into oral solid dosage forms (OSDs), challenges surrounding their ease of handling and manufacture must be addressed. To this end a framework for transforming API-ILs into solid forms at high loadings based on spray encapsulation using an immiscible polymer has recently been demonstrated. The current work demonstrates that this framework can be applied to a broad range of newly synthesized low glass transition temperature (T_g) API-ILs. Furthermore, the work explores a second novel approach to solidification of API-ILs based on polymer-API-IL miscibility that, to the best of our knowledge, has not been previously demonstrated. Modulated differential scanning calorimetry (mDSC) and attenuated total reflectance Fourier transform infrared spectroscopy showed that it was possible to produce spray dried solid materials, at acceptable loadings and yields for OSD applications in the form of both two-phase phase encapsulated systems and single phase amorphous solid dispersions (ASDs). This was achieved by the appropriate selection of an API-IL insoluble polymer (ethyl cellulose) for phase separated systems, or a miscible polymer with an exceptionally high T_g (the polysaccharide, maltodextrin) for the ASDs. Both approaches successfully overcame the T_g suppression associated with room temperature ILs. This work represents the first step to understanding the fundamental critical physical attributes of these systems to facilitate a more mechanistic methodology for their design.

Natural sesame oil is superior to pre-digested lipid formulations and purified triglycerides in promoting the intestinal lymphatic transport and systemic bioavailability of cannabidiol

Lipid-based formulations play a significant role in oral delivery of lipophilic drugs. Previous studies have shown that natural sesame oil promotes the intestinal lymphatic transport and oral bioavailability of the highly lipophilic drug cannabidiol (CBD). However, both lymphatic transport and systemic bioavailability were also associated with considerable variability. The aim of this study was to test the hypothesis that pre-digested lipid formulations (oleic acid, linoleic acid, oleic acid with 2-oleoylglycerol, oleic acid with 2-oleoylglycerol and oleic acid with glycerol) could reduce variability and increase the extent of the intestinal lymphatic transport and oral bioavailability of CBD. The in vivo studies in rats showed that pre-digested or purified triglyceride did not improve the lymphatic transport and bioavailability of CBD in comparison to sesame oil. Moreover, the results suggest that both the absorption of lipids and the absorption of co-administered CBD were more efficient following administration of natural sesame oil vehicle compared with pre-digested lipids or purified trioleate. Although multiple small molecule constituents and unique fatty acid compositions could potentially contribute to a better performance of sesame oil in oral absorption of lipids or CBD, further investigation will be needed to identify the mechanisms involved.

Estimating the Oral Absorption from Self-Nanoemulsifying Drug Delivery Systems Using an In Vitro Lipolysis-Permeation Method

The aim of this study was to design an in vitro lipolysis-permeation method to estimate drug absorption following the oral administration of self-nanoemulsifying drug delivery systems (SNEDDSs). The method was evaluated by testing five oral formulations containing cinnarizine (four SNEDDSs and one aqueous suspension) from a previously published pharmacokinetic study in rats. In that study, the pharmacokinetic profiles of the five formulations did not correlate with the drug solubilization profiles obtained during in vitro intestinal lipolysis. Using the designed lipolysis-permeation method, in vitro lipolysis of the five formulations was followed by in vitro drug permeation in Franz diffusion cells equipped with PermeaPad^® barriers. A linear in vivo–in vitro correlation was obtained when comparing the area under the in vitro drug permeation–time curve (AUC_0–3h), to the AUC_0–3h of the plasma concentration–time profile obtained from the in vivo study. Based on these results, the evaluated lipolysis-permeation method was found to be a promising tool for estimating the in vivo performance of SNEDDSs, but more studies are needed to evaluate the method further.

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.

Mechanisms of drug solubilization by polar lipids in biorelevant media

Despite the widespread use of lipid excipients in both academic research and oral formulation development, rational selection guidelines are still missing. In the current study, we aimed to establish a link between the molecular structure of commonly used polar lipids and drug solubilization in biorelevant media. The solubilization of fenofibrate by 13 phospholipids, 11 fatty acids and 2 monoglycerides was studied by an in vitro model of the upper GI tract. The main trends were verified with progesterone and danazol. It was revealed that to alter drug solubilization in biorelevant media, the polar lipids must form mixed colloidal aggregates with the bile. Such aggregates are formed when: (1) the polar lipid is used at a sufficiently high concentration (relative to its mixed critical micellar concentration) and (2) its hydrophobic chain has a melting temperature (T_m) < 37 °C. When these two conditions are met, the increased polar lipid chain length increases the drug solubilization capacity. Hence, long chain (C18) unsaturated polar lipids show best drug solubilization, due to the combination of long chain length and low T_m. Polar lipids with T_m significantly higher than 37 °C (e.g. C16 and C18 saturated compounds) do not impact drug solubilization in biorelevant media, due to limited association in mixed colloidal aggregates. The hydrophilic head group also has a dramatic impact on the drug solubilization enhancement, with polar lipids performance decreasing in the order [choline phospholipids] > [monoglycerides] > [fatty acids]. As both the acyl chain and head group types are structural features of the polar lipids, and not of the solubilized drugs, the described trends in drug solubilization should hold true for a variety of hydrophobic molecules.

Current challenges and future perspectives in oral absorption research: An opinion of the UNGAP network

Although oral drug delivery is the preferred administration route and has been used for centuries, modern drug discovery and development pipelines challenge conventional formulation approaches and highlight the insufficient mechanistic understanding of processes critical to oral drug absorption. This review presents the opinion of UNGAP scientists on four key themes across the oral absorption landscape: (1) specific patient populations, (2) regional differences in the gastrointestinal tract, (3) advanced formulations and (4) food-drug interactions. The differences of oral absorption in pediatric and geriatric populations, the specific issues in colonic absorption, the formulation approaches for poorly water-soluble (small molecules) and poorly permeable (peptides, RNA etc.) drugs, as well as the vast realm of food effects, are some of the topics discussed in detail. The identified controversies and gaps in the current understanding of gastrointestinal absorption-related processes are used to create a roadmap for the future of oral drug absorption research.

Improvement of the bioavailability of curcumin by a supersaturatable self nanoemulsifying drug delivery system with incorporation of a hydrophilic polymer: in vitro and in vivo characterisation

OBJECTIVES

The current study was focused on preparing curcumin (CUR) supersaturated self-nano-emulsion (PI-CUR-SNEDDS) using hydrophilic polymer and to study the influence of polymer precipitation inhibitor on the physicochemical and biopharmaceutical properties of the PI-CUR-SNEDDS.

METHODS

PI-CUR-SNEDDS were prepared using hydrophilic polymer in order to maintain the supersaturation of CUR in nano-emulsion solution, artificial gastrointestinal fluid (AGF), and the precipitates formed, and characterised by in vitro dispersion tests, in vitro intestinal absorption and in vivo pharmacokinetic and compared with CUR-SNEDDS.

KEY FINDINGS

PI-CUR-SNEDDS prepared with 2% hydroxypropyl methylcellulose 55-60 (HPMC55-60) as precipitation inhibitor (PI) significantly improved the viscosity, physical stability and CUR's equilibrium solubility of nanoemulsion. HPMC55-60 and CUR interact in AGF through intermolecular interactions, form hydrogen bonds, and produce amorphous precipitates. Compared with CUR-SNEDDS, the proportion of CUR in the hydrophilic phase increased by about 3-fold, and apparent permeability coefficient (Papp) in duodenum, jejunum, ileum, and colon increased by 2.30, 3.65, 1.54 and 2.08-fold, respectively, and the area under the plasma concentration-time curve0-12h of PI-CUR-SNEDDS also increased by 3.50-fold.

CONCLUSIONS

Our results suggested that HPMC55-60 maintained the CUR supersaturation state by forming hydrogen bonds with CUR, increasing the solution's viscosity and drug solubilisation, thus improving the absorption and bioavailability of CUR.

In Vivo T Cell-Targeting Nanoparticle Drug Delivery Systems: Considerations for Rational Design

T cells play an important role in immunity and repair and are implicated in diseases, including blood cancers, viral infections, and inflammation, making them attractive targets for the treatment and prevention of diseases. Over recent years, the advent of nanomedicine has shown an increase in studies that use nanoparticles as carriers to deliver therapeutic cargo to T cells for ex vivo and in vivo applications. Nanoparticle-based delivery has several advantages, including the ability to load and protect a variety of drugs, control drug release, improve drug pharmacokinetics and biodistribution, and site- or cell-specific targeting. However, the delivery of nanoparticles to T cells remains a major technological challenge, which is primarily due to the nonphagocytic nature of T cells. In this review, we discuss the physiological barriers to effective T cell targeting and describe the different approaches used to deliver cargo-loaded nanoparticles to T cells for the treatment of disease such as T cell lymphoma and human immunodeficiency virus (HIV). In particular, engineering strategies that aim to improve nanoparticle internalization by T cells, including ligand-based targeting, will be highlighted. These nanoparticle engineering approaches are expected to inspire the development of effective nanomaterials that can target or manipulate the function of T cells for the treatment of T cell-related diseases.

Medical food development by dietetic management of the endocannabinoid system through dietary sources of β-caryophyllene

Objective: To research the biological impact on the endocannabinoid system (ECS) from dietary sources of [Formula: see text]-caryophyllene (BCP). This will encompass pre-clinical and clinical research for BCP. The bioavailability of BCP will be explored, focusing on bioavailability improvement. This research will establish if there is justification to warrant the development of a medical food for supporting the ECS through dietetic supplementation of BCP.

Methods: Research and review papers were identified through the search engines Google Scholar, PubMed, and ScienceDirect. Main keywords included [Formula: see text]-caryophyllene, endocannabinoid system, dietary cannabinoids, cannabinoid type-2 receptor, and bioavailability.

Results: The human body is limited in the digestion of BCP from food. This is because BCP is poorly absorbed in the gut. Everyone has different underlying endocannabinoid efficiency and most people do not have the full potential of supporting their ECS through diet.

Conclusion: A medical food can be developed to use BCP with a delivery system, so that the bioactive food cannabinoid is readily absorbed. This will deliver dietary support to the ECS, that otherwise would be available from food.

This review provides insight into the efficacy of using BCP in medical foods as dietary support for the ECS. Supporting the ECS can assist in maintaining homeostasis, regulating immune function, pain intensity, inflammatory markers, sleep patterns, mood, appetite, and stress susceptibility.

Digestion of Lipid-Based Formulations Not Only Mediates Changes to Absorption of Poorly Soluble Drugs Due to Differences in Solubilization But Also Reflects Changes to Thermodynamic Activity and Permeability

The aim of this study was to evaluate the effect of lipid digestion on the permeability and absorption of orally administered saquinavir (SQV), a biopharmaceutics classification system (BCS) class IV drug, in different lipid-based formulations. Three LBFs were prepared: a mixed short- and medium-chain lipid-based formulation (SMCF), a medium-chain lipid-based formulation (MCF), and a long-chain lipid-based formulation (LCF). SQV was loaded into these LBFs at 26.7 mg/g. To evaluate the pharmacokinetics of SQV in vivo, drug-loaded formulations were predispersed in purified water at 3% w/w and orally administered to rats. A low dose (0.8 mg/rat) was employed to limit confounding effects on drug solubilization, and consistent with this design, presolubilization of SQV in the LBFs did not increase in vivo exposure compared to a control suspension formulation. The areas under the plasma concentration-time curve were, however, significantly lower after administration of SQV as MCF and LCF compared to SMCF. To evaluate the key mechanisms underpinning absorption, each LBF containing SQV was digested, and the flux of SQV from the digests across a dialysis membrane was evaluated in in vitro permeation experiments. This study revealed that the absorption profiles were driven by the free concentration of SQV and that this varied due to differences in SQV solubilization in the digestion products generated by LBF digestion. The apparent first-order permeation rate constants of SQV (k_app,total) were estimated by dividing the flux of SQV in the dialysis membrane experiments by the concentration of total SQV on the donor side. k_app,total values strongly correlated with in vivo AUC. The data provide one of the first studies of the effect of digestion products on the free concentration of a drug in the GI fluid and oral absorption. This simple permeation model may be a useful tool for the evaluation of the impact of lipid digestion on apparent drug permeability from lipid-based formulations. These effects should be assessed alongside, and in addition to, the more well-known effects of lipids on enhancing intestinal solubilization of poorly water-soluble drugs.

Taking Particle Tracking into Practice by Novel Software and Screening Approach: Case-Study of Oral Lipid Nanocarriers

The success on the design of new oral nanocarriers greatly depends on the identification of the best physicochemical properties that would allow their diffusion across the mucus layer that protects the intestinal epithelium. In this context, particle tracking (PT) has arisen in the pharmaceutical field as an excellent tool to evaluate the diffusion of individual particles across the intestinal mucus. In PT, the trajectories of individual particles are characterized by the mean square displacement (MSD), which is used to calculate the coefficient of diffusion (D) and the anomalous diffusion parameter (α) as MSD=4Dτα. Unfortunately, there is no stablished criteria to evaluate the goodness-of-fit of the experimental data to the mathematical model. This work shows that the commonly used R2 parameter may lead to an overestimation of the diffusion capacity of oral nanocarriers. We propose a screening approach based on a combination of R2 with further statistical parameters. We have analyzed the effect of this approach to study the intestinal mucodiffusion of lipid oral nanocarriers, compared to the conventional screening approach. Last, we have developed software able to perform the whole PT analysis in a time-saving, user-friendly, and rational fashion.

Rational Selection of Bio-Enabling Oral Drug Formulations - A PEARRL Commentary

New drug candidates often require bio-enabling formation technologies such as lipid-based formulations, solid dispersions, or nanosized drug formulations. Development of such more sophisticated delivery systems generally requires higher resource investment compared to a conventional oral dosage form, which might slow down clinical development. To achieve the biopharmaceutical objectives while enabling rapid cost effective development, it is imperative to identify a suitable formulation technique for a given drug candidate as early as possible. Hence many companies have developed internal decision trees based mostly on prior organizational experience, though they also contain some arbitrary elements. As part of the EU funded PEARRL project, a number of new decision trees are here proposed that reflect both the current scientific state of the art and a consensus among the industrial project partners. This commentary presents and discusses these, while also going beyond this classical expert approach with a pilot study using emerging machine learning, where the computer suggests formulation strategy based on the physicochemical and biopharmaceutical properties of a molecule. Current limitations are discussed and an outlook is provided for likely future developments in this emerging field of pharmaceutics.

Stabilising disproportionation of lipophilic ionic liquid salts in lipid-based formulations

Lipid based formulations (LBFs) can enhance oral bioavailability, however, their utility may be restricted by low drug loading in the formulation. Converting drugs to drug-ionic liquids (drug-ILs) or lipophilic salts can significantly increase lipid solubility but this approach is complicated in some cases by salt disproportionation, leading to a reduction in solubility and physical instability. Here we explore the physical stability of the weakly basic model drug, cinnarizine (CIN), when paired with a decanoate counterion (Dec) to form the drug-IL, cinnarizine decanoate (CIN.Dec). Consistent with published studies of salt disproportionation in aqueous solution, weakly acidic counterions such as Dec lead to the generation of drug-IL lipid solutions with pHs below pH_max. This leads to CIN deprotonation to the less soluble free base and precipitation. Subsequent studies however, show that these effects can be reversed by acidification of the formulation (either with excess decanoic acid or other lipid soluble acids), stimulating a pH shift to the salt plateau of CIN.Dec and the formation of stable lipid solutions of CIN.Dec. Altering formulation pH to more acidic conditions, therefore stabilises drug-ILs formed using weakly acidic lipophilic counterions, and is a viable method to promote formulation stability via inhibition of disproportionation of some drug-ILs.

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.

Effects of Lipid Digestion and Drug Permeation/Re-Dissolution on Absorption of Orally Administered Ritonavir as Different Lipid-Based Formulations

The aim of this study is to clarify absorption mechanisms after oral administration of ritonavir (RTV) from different types of lipid-based formulations (LBFs) with particular emphasis on the effect of lipid digestion and drug permeation/re-dissolution on the oral absorption. Four LBFs were prepared; three contained either long-chain (LC) or medium-chain (MC) lipids [lipid formulation classification system (LFCS) Type II-LC, Type IIIA-MC, and Type IIIB-MC] and the fourth contained only surfactant and co-solvent (Type IV). The solubility of RTV in those LBFs was determined and drug subsequently loaded at 85% w/w of the saturated solubility in the formulations. Then, each LBF containing drug was added into a model rat intestinal fluid at approximately 2.5% w/v for evaluation using an in vitro digestion model. In vitro digestion study showed the ability of Type II-LC and Type IIIA-MC to support continued solubilization of RTV, and moderate supersaturation was observed in Type IIIA-MC. In contrast, RTV partly precipitated in the Type IIIB-MC during digestion, and the Type IV formulation lost its solubilization capacity rapidly upon dispersion, leading to drastic precipitation. Oral administration of RTV as Type IIIA-MC to rats showed significantly higher area under the plasma concentration-time curve compared to control suspension, whereas it was not improved with Type II-LC administration despite complete solubilization of RTV during digestion. From the results of in vitro permeation across dialysis membrane (a molecular weight cutoff of > 1000 Da), this may be attributed to the lowered free concentration in the gastrointestinal tract owing to incorporation of RTV into the undigested LC lipid. Oral absorption drastically increased with Type IIIB-MC and Type IV despite the observed moderate and drastic precipitation, respectively. Powder X-ray diffraction analysis revealed that the precipitate was amorphous. Therefore, improved re-solubilization may partly contribute to improved absorption. The present study revealed detailed absorption mechanisms from LBFs with different compositions. Our findings may be useful for selecting appropriate excipients to design optimal LBFs for poorly water-soluble drugs.

New lipophenols prevent carbonyl and oxidative stresses involved in macular degeneration

Dry age-related macular degeneration and Stargardt disease undergo a known toxic mechanism caused by carbonyl and oxidative stresses (COS). This is responsible for accumulation in the retinal pigment epithelium (RPE) of A2E, a main toxic pyridinium bis-retinoid lipofuscin component. Previous studies have shown that carbonyl stress in retinal cells could be reduced by an alkyl-phloroglucinol-DHA conjugate (lipophenol). Here, we performed a rational design of different families of lipophenols to conserve anti-carbonyl stress activities and improve antioxidant properties. Five synthetic pathways leading to alkyl-(poly)phenol derivatives, with phloroglucinol, resveratrol, catechin and quercetin as the main backbone, linked to poly-unsaturated fatty acid, are presented. These lipophenols were evaluated in ARPE-19 cell line for their anti-COS properties and a structure-activity relationship study is proposed. Protection of ARPE-19 cells against A2E toxicity was assessed for the four best candidates. Finally, interesting anti-COS properties of the most promising quercetin lipophenol were confirmed in primary RPE cells.

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.

Effect of excipients on oral absorption process according to the different gastrointestinal segments

INTRODUCTION

Excipients are necessary to develop oral dosage forms of any Active Pharmaceutical Ingredient (API). Traditionally, excipients have been considered inactive and inert substances, but, over the years, numerous studies have contradicted this belief. This review focuses on the effect of excipients on the physiological variables affecting oral absorption along the different segments of the gastrointestinal tract. The effect of excipients on the segmental absorption variables are illustrated with examples to help understand the complexity of predicting their in vivo effects.

AREAS COVERED

The effects of excipients on disintegration, solubility and dissolution, transit time, and absorption are analyzed in the context of the different gastrointestinal segments and the physiological factors affecting release and membrane permeation. The experimental techniques used to study excipient effects and their human predictive ability are reviewed.

EXPERT OPINION

The observed effects of excipient in oral absorption process have been characterized in the past, mainly in vitro (i.e. in dissolution studies, in vitro cell culture methods or in situ animal studies). Unfortunately, a clear link with their effects in vivo, i.e. their impact on Cmax or AUC, which need a mechanistic approach is still missing. The information compiled in this review leads to the conclusion that the effect of excipients in API oral absorption and bioavailability is undeniable and shows the need of implementing standardized and reproducible preclinical tools coupled with mechanistic and predictive physiological-based models to improve the current empirical retrospective approach.

Synergistic Computational Modeling Approaches as Team Players in the Game of Solubility Predictions

Several approaches to predict and model drug solubility have been used in the drug discovery and development processes during the last decades. Each of these approaches have their own benefits and place, and are typically used as standalone approaches rather than in concert. The synergistic effects of these are often overlooked, partly due to the need of computational experts to perform the modeling and simulations as well as analyzing the data obtained. Here we provide our views on how these different approaches can be used to retrieve more information on drug solubility, ranging from multivariate data analysis over thermodynamic cycle modeling to molecular dynamics simulations. We are discussing aqueous solubility as well as solubility in more complex mixed solvents and media with colloidal structures present. We conclude that the field of computational pharmaceutics is in its early days but with a bright future ahead. However, education of computational formulators with broad knowledge of modeling and simulation approaches is imperative if computational pharmaceutics is to reach its full potential.

Applying Computational Predictions of Biorelevant Solubility Ratio Upon Self-Emulsifying Lipid-Based Formulations Dispersion to Predict Dose Number

Computational approaches are increasingly utilised in development of bio-enabling formulations, including self-emulsifying drug delivery systems (SEDDS), facilitating early indicators of success. This study investigated if in silico predictions of drug solubility gain i.e. solubility ratios (SR), after dispersion of a SEDDS in biorelevant media could be predicted from drug properties. Apparent solubility upon dispersion of two SEDDS in FaSSIF was measured for 30 structurally diverse poorly water soluble drugs. Increased drug solubility upon SEDDS dispersion was observed in all cases, with higher SRs observed for cationic and neutral versus anionic drugs at pH 6.5. Molecular descriptors and solid-state properties were used as inputs during partial least squares (PLS) modelling resulting in predictive models for SR_MC (r² = 0.81) and SR_LC (r² = 0.77). Multiple linear regression (MLR) facilitated generation of simplified SR equations with high predictivity (SR_MC r² = 0.74; SR_LC r² = 0.69), requiring only three drug properties; partition coefficient at pH 6.5 (logD_6.5), melting point (Tm) and aromatic bonds as fraction of total bonds (F-AromB). Through using the equations to inform developability classification system (DCS) classes for drugs that have already been licensed as lipid-based formulations, merits for development with SEDDS was predicted for 2/3 drugs.