Physico-chemical characterization of self-emulsifying drug delivery systems

Fabrication of controlled-release polymeric microneedles containing progesterone-loaded self-microemulsions for transdermal delivery

Progesterone (PG) has been approved for hormone replacement therapy to mitigate the risk of endometrial carcinoma. However, there has been a lack of success in oral PG due to its rapid degradation. Transdermal PG has advantages but lacks efficacy due to its poor solubility (Log p = 3.9). Therefore, this study aimed to evaluate how combining self-microemulsifying drug delivery systems (SMEDDS) and polymeric microneedles (MNs) could improve the transdermal delivery of PG in a controlled-release manner. Among PG-SMEDDS, PG-SME5 was selected for its desirable properties and stability. The two-layer polymeric MNs formulation incorporating PG-SME5 (PG-SMEDDS-tMNs) was formulated from aqueous blends of polymers as a first layer and 20% PCL as a second layer. It successfully penetrated neonatal porcine skin with the dissolution of the first layer observed within 15 min after application. In vitro skin permeation revealed that the percentage of PG which permeated the skin over 82 h using PG-SMEDDS-tMNs was higher than a PG-suspension and PG-SMEDDS. The Higuchi kinetic showed controlled release over 15 days of PG from PG-SMEDDS-tMNs. These studies suggested that incorporating PG-SMEDDS into controlled-release two-layer polymeric MNs could be a promising approach for improving the transdermal delivery of PG.

Natural products in traditional Chinese medicine: molecular mechanisms and therapeutic targets of renal fibrosis and state-of-the-art drug delivery systems

Renal fibrosis (RF) is the end stage of several chronic kidney diseases. Its series of changes include excessive accumulation of extracellular matrix, epithelial-mesenchymal transition (EMT) of renal tubular cells, fibroblast activation, immune cell infiltration, and renal cell apoptosis. RF can eventually lead to renal dysfunction or even renal failure. A large body of evidence suggests that natural products in traditional Chinese medicine (TCM) have great potential for treating RF. In this article, we first describe the recent advances in RF treatment by several natural products and clarify their mechanisms of action. They can ameliorate the RF disease phenotype, which includes apoptosis, endoplasmic reticulum stress, and EMT, by affecting relevant signaling pathways and molecular targets, thereby delaying or reversing fibrosis. We also present the roles of nanodrug delivery systems, which have been explored to address the drawback of low oral bioavailability of natural products. This may provide new ideas for using natural products for RF treatment. Finally, we provide new insights into the clinical prospects of herbal natural products.

Development of Environmentally Responsive Self-Emulsifying System Containing Copaiba Oil-Resin for Leishmaniasis Oral Treatment

Leishmaniasis is a disease caused by protozoa species of the Leishmania genus, and the current treatments face several difficulties and obstacles. Most anti-leishmanial drugs are administered intravenously, showing many side effects and drug resistance. The discovery of new anti-leishmanial compounds and the development of new pharmaceutical systems for more efficient and safer treatments are necessary. Copaiba oil-resin (CO) has been shown to be a promising natural compound against leishmaniasis. However, CO displays poor aqueous solubility and bioavailability. Self-emulsifying drug delivery systems (SEDDS) can provide platforms for release of hydrophobic compounds in the gastrointestinal tract, improving their aqueous solubilization, absorption and bioavailability. Therefore, the present work aimed to develop SEDDS containing CO and Soluplus® surfactant for the oral treatment of leishmaniasis. The design of the systems was accomplished using ternary phase diagrams. Emulsification and dispersion time tests were used to investigate the emulsification process in gastric and intestinal environments. The formulations were nanostructured and improved the CO solubilization. Their in vitro antiproliferative activity against promastigote forms of L. amazonensis and L. infantum, and low in vitro cytotoxicity against macrophages were also observed. More studies are necessary to determine effectiveness of SOL in these systems, which can be candidates for further pharmacokinetics and in vivo investigations.

Nanotechnology-based ocular drug delivery systems: recent advances and future prospects

Ocular drug delivery has constantly challenged ophthalmologists and drug delivery scientists due to various anatomical and physiological barriers. Static and dynamic ocular barriers prevent the entry of exogenous substances and impede therapeutic agents' active absorption. This review elaborates on the anatomy of the eye and the associated constraints. Followed by an illustration of some common ocular diseases, including glaucoma and their current clinical therapies, emphasizing the significance of drug therapy in treating ocular diseases. Subsequently, advances in ocular drug delivery modalities, especially nanotechnology-based ocular drug delivery systems, are recommended, and some typical research is highlighted. Based on the related research, systematic and comprehensive characterizations of the nanocarriers are summarized, hoping to assist with future research. Besides, we summarize the nanotechnology-based ophthalmic drugs currently on the market or still in clinical trials and the recent patents of nanocarriers. Finally, inspired by current trends and therapeutic concepts, we provide an insight into the challenges faced by novel ocular drug delivery systems and further put forward directions for future research. We hope this review can provide inspiration and motivation for better design and development of novel ophthalmic formulations.

Insights into Lipid-Based Delivery Nanosystems of Protein-Tyrosine Kinase Inhibitors for Cancer Therapy

According to the WHO, cancer caused almost 10 million deaths worldwide in 2020, i.e., almost one in six deaths. Among the most common are breast, lung, colon and rectal and prostate cancers. Although the diagnosis is more perfect and spectrum of available drugs is large, there is a clear trend of an increase in cancer that ends fatally. A major advance in treatment was the introduction of gentler antineoplastics for targeted therapy-tyrosine kinase inhibitors (TKIs). Although they have undoubtedly revolutionized oncology and hematology, they have significant side effects and limited efficacy. In addition to the design of new TKIs with improved pharmacokinetic and safety profiles, and being more resistant to the development of drug resistance, high expectations are placed on the reformulation of TKIs into various drug delivery lipid-based nanosystems. This review provides an insight into the history of chemotherapy, a brief overview of the development of TKIs for the treatment of cancer and their mechanism of action and summarizes the results of the applications of self-nanoemulsifying drug delivery systems, nanoemulsions, liposomes, solid lipid nanoparticles, lipid-polymer hybrid nanoparticles and nanostructured lipid carriers used as drug delivery systems of TKIs obtained in vitro and in vivo.

SEDDS Basic Design and Recent Formulation Advancement: A Concurrent Review

In the present scenario, lipid-based novel drug delivery systems are the area of interest for the formulation scientist in order to improve the bioavailability of poorly water-soluble drugs. A selfemulsifying drug delivery system (SEDDS) upon contact with the gastrointestinal fluid, forms an o/w emulsion. SEDDS has gained popularity as a potential platform for improving the bioavailability of the lipophilic drug by overcoming several challenges. The various advantages like improved solubility, bypassing lymphatic transport, and improvement in bioavailability are associated with SMEDDS or SNEDDS. The extent of the formation of stable SEDDS depends on a specific combination of surfactant, co-surfactant, and oil. The present review highlighted the different aspects of formulation design along with optimization and characterization of SEDDS formulation. It also gives a brief description of the various aspects of the excipients used in SEDDS formulation. This review also includes the conflict between types of SEDDS based on droplet size. There is an extensive review of various research regarding different solidification techniques used for SEDDS in the last three years.

Baicalein self-microemulsion based on drug-phospholipid complex for the alleviation of cytokine storm

Cytokine storm is a phenomenon whereby the overreaction of the human immune system leads to the release of inflammatory cytokines, which can lead to multiple organ dysfunction syndrome. At present, the existing drugs for the treatment of cytokine storm have limited efficacy and severe adverse effects. Here, we report a lymphatic targeting self-microemulsifying drug delivery system containing baicalein to effectively inhibit cytokine storm. Baicalein self-microemulsion with phospholipid complex as an intermediate carrier (BAPC-SME) prepared in this study could be spontaneously emulsified to form 12-nm oil-in-water nanoemulsion after administration. And then BAPC-SME underwent uptake by enterocyte through endocytosis mediated by lipid valve and clathrin, and had obvious characteristics of mesenteric lymph node targeting distribution. Oral administration of BAPC-SME could significantly inhibit the increase in plasma levels of 14 cytokines: TNF-α, IL-6, IFN-γ, MCP-1, IL-17A, IL-27, IL-1α, GM-CSF, MIG, IFN-β, IL-12, MIP-3α, IL-23, and RANTES in mice experiencing systemic cytokine storm. BAPC-SME could also significantly improve the pathological injury and inflammatory cell infiltration of lung tissue in mice experiencing local cytokine storm. This study does not only provide a new lymphatic targeted drug delivery strategy for the treatment of cytokine storm but also has great practical significance for the clinical development of baicalein self-microemulsion therapies for cytokine storm.

Self-emulsifying drug delivery systems: a novel approach to deliver drugs

Self-emulsifying drug delivery systems (SEDDS) are a proven method for poorly soluble substances works by increasing the solubility and bioavailability. SEDDS and isotropic mixtures, are composed of oils, surfactants, and occasionally cosolvents. The ability of these formulations and methods to produce microemulsions or fine oil-in-water (o/w) emulsions after moderate stirring and dilution by water phase along the GI tract might be a promising technique for lipophilic agents with dissolution rate-limited absorption. This review provides an outline of SEDDS's numerous advances and biopharmaceutical elements, types, manufacturing, characterization, limitations, and future prospects. The evaluation of SEDDS and its applications are also discussed, focusing on the advances of SEDDS's solid self-emulsifying delivery mechanism and dosage form. By integrating suitable polymer into the formulation, SEDDS may be studied for the creation of a formulation with sustained drug release. This technology's improvement might lead to a new application in the field of medicine delivery. SEDDS has been demonstrated to be quite efficient in increasing oral bioavailability of lipophilic products. SEDDS is one of the promising methods for controlling the characteristics of medications that are not great choices for oral delivery. It is also worth mentioning that SEDDS may be made in variety of solid dosage forms that are acceptable for both oral and parenteral administration.

Self-Emulsifying Systems for Delivery of Bioactive Compounds from Natural Origin

Nature has been used as therapeutic resources in the treatment of diseases for many years. However, some natural compounds have poor water solubility. Therefore, physicochemical strategies and technologies are necessary for development of systems for carrying these substances. The self-emulsifying drug delivery systems (SEDDS) have been used as carriers of hydrophobic compounds in order to increase the solubility and absorption, improving their bioavailability. SEDDS are constituted with a mixture of oils and surfactants which, when come into contact with an aqueous medium under mild agitation, can form emulsions. In the last years, a wide variety of self-emulsifying formulations containing bioactive compounds from natural origin has been developed. This review provides a comprehensive overview of the main excipients and natural bioactive compounds composing SEDDS. In addition, applications, new technologies and innovation are reviewed as well. Examples of self-emulsifying formulations administered in different sites are also considered for a better understanding of the use of this strategy to modify the delivery of compounds from natural origin.

Preparation and Evaluation of Novel Supersaturated Solid Dispersion of Magnolol : Theme: Advancements in Amorphous Solid Dispersions to Improve Bioavailability

This article aimed to design a new type of supersaturated solid dispersion (NS-SD) loaded with Magnolol (Mag) to raise the oral bioavailability in rats. In the light of the solubility parameters, phase solubility experiments, inhibition precipitation experiment, and in vitro release experiment, Plasdone-630 (PS-630) was selected as the optimum carrier. In addition, Mag-NS-SD was prepared by adding Monoglyceride (MG) and Lecithin High Potency (LHP) into the Mag-S-SD (Mag:PS-630 = 1:3), so as to reduce the dosage of carrier and improve the release rate. Using central composite design of response surface method, the prescription was further optimized. As the optimized condition was Mag:PS-630: MG: LHP = 1:3:0.8:0.266, the drug release rate was the fastest. Besides, after 45 min, the release rate was nearly 100%. The constructed Mag-S-SD and Mag-NS-SD were characterized by powder X-ray diffraction and infrared absorption spectrum. The XRD patterns of Mag-S-SD and Mag-NS-SD indicated that all APIs were amorphous. The IR spectra of Mag-S-SD and Mag-NS-SD demonstrated the existence of hydrogen bonding in the systems. Furthermore, in vivo pharmacokinetic study in rats revealed that compared with Mag and Mag-S-SD, Mag-NS-SD significantly increased the bioavailability (the relative bioavailability was 213.69% and 142.37%, separately). In this study, Mag-NS-SD was successfully prepared, which could improve the oral bioavailability and may increase the clinical application.

Nanoemulsion delivery systems for enhanced efficacy of antimicrobials and essential oils

The ever-growing threat of new and existing infectious diseases in combination with antimicrobial resistance requires the need for innovative and effective forms of drug delivery. Optimal drug delivery systems for existing and newly developed antimicrobials can enhance drug bioavailability, enable site-specific drug targeting, and overcome current limitations of drug formulations such as short elimination half-lives, poor drug solubility, and undesirable side effects. Nanoemulsions (NE) consist of nanometer-sized droplets stabilized by emulsifiers and are typically more stable and permeable due to their smaller particle sizes and higher surface area compared to conventional emulsions. NE have been identified as a promising means of antimicrobial delivery due to their intrinsic antimicrobial properties, ability to increase drug solubility, stability, bioavailability, organ and cellular targeting potentials, capability of targeting biofilms, and potential to overcome antimicrobial resistance. Herein, we discuss non-drug loaded essential oil-based NE that can confer antimicrobial actions through predominantly physical or biochemical mechanisms without drug payloads. We also describe drug-loaded NE for enhanced antimicrobial efficacy by augmenting the potency of existing antimicrobials. We highlight the versatility of NE to be administered through multiple different routes (oral, parenteral, dermal, transdermal, pulmonary, nasal, ocular, and rectal). We summarize recent advances in the clinical translation of antimicrobial NE and shed light on future development of effective antimicrobial therapy to combat infectious diseases.

Famotidine-loaded solid self-nanoemulsifying drug delivery system demonstrates exceptional efficiency in amelioration of peptic ulcer

Famotidine (FMD) is a highly potent H₂-receptor antagonist used in peptic ulcer treatment. However, the drug possesses poor aqueous solubility and permeability. FMD-loaded solid self-nanoemulsifying drug delivery system (FMD-S-SNEDDS) comprised of Labrafil® M 1944 CS, Tween® 20 and PEG 400, adsorbed on Aerosil® 200, has been developed. FMD-S-SNEDDS has demonstrated acceptable micromeritic properties, and upon reconstitution in water, spherical nanosized particles were released, as demonstrated by dynamic light scattering studies and transmission electron microscopy imaging. High encapsulation efficiency of FMD in the developed SNEDDS has been attained, and the saturated solubility of the drug has increased by 20-fold when it was incorporated in the SNEDDS. Several in vitro characterizations have been carried out, including, Fourier transform-infrared spectroscopy, differential scanning calorimetry, scanning electron microscopy, and drug dissolution studies. In vivo, upon administration of the free drug suspension, marketed product (FAMOTIN®) and FMD-S-SNEDDS (40 mg/kg) in peptic ulcer rat models, FMD-S-SNEDDS and the marketed FMD demonstrated 12.5- and 4.7-fold reduction in ulcers number, and 28.7- and 7.2-fold reduction in ulcer severity, respectively, compared to the control untreated animals. FMD-S-SNEDDS showed a significant (p < 0.05) increase in the levels of depleted glutathione and endothelial nitric oxide synthase, and significantly (p < 0.05) reduced the elevated level of malondialdehyde, as compared to the free and marketed FMD. Only FMD-S-SNEDDS could restore the elevated proton pump activity and cyclic adenosine monophosphate RNA expression to their normal levels. Hence, FMD-S-SNEDDS provides a great potential as a nanotherapeutic system for treatment of peptic ulcer.

Colloidal and vesicular delivery system for herbal bioactive constituents

OBJECTIVES

The main objective of the present review is to explore and examine the effectiveness of currently developed novel techniques to resolve the issues which are associated with the herbal constituents/extract.

METHODS

A systematic thorough search and collection of reviewed information from Science direct, PubMed and Google Scholar databases based on various sets of key phrases have been performed. All the findings from these data have been studied and briefed based on their relevant and irrelevant information.

RESULT

Herbal drugs are gaining more popularity in the modern world due to their applications in curing various ailments with minimum toxic effects, side effect or adverse effect. However, various challenges exist with herbal extracts/plant actives such as poor solubility (water/lipid), poor permeation, lack of targeting specificity, instability in highly acidic pH, and liver metabolism, etc. Nowadays with the expansion in the technology, novel drug delivery system provides avenues and newer opportunity towards the delivery of herbal drugs with improved physical chemical properties, pharmacokinetic and pharmacodynamic. Developing nano-strategies like Polymeric nanoparticles, Liposomes, Niosomes, Microspheres, Phytosomes, Nanoemulsion and Self Nano Emulsifying Drug Delivery System, etc. imparts benefits for delivery of phyto formulation and herbal bioactives. Nano formulation of phytoconstituents/ herbal extract could lead to enhancement of aqueous solubility, dissolution, bioavailability, stability, reduce toxicity, permeation, sustained delivery, protection from enzymatic degradation, etc. CONCLUSION: Based on the above findings, the conclusion can be drawn that the nano sized novel drug delivery systems of herbal and herbal bioactives have a potential future for upgrading the pharmacological action and defeating or overcoming the issues related with these constituents. The aims of the present review was to summarize and critically analyze the recent development of nano sized strategies for promising phytochemicals delivery systems along with their therapeutic applications supported by experimental evidence and discussing the opportunities for further aspects.

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.

Development of New Indonesian Propolis Extract-Loaded Self-emulsifying: Characterization, Stability and Antibacterial Activity

Purpose: This study aimed to prepare, characterize, examine the stability and evaluation of the antibacterial activity of Indonesian propolis extract-loaded self-emulsifying (PESE).

Methods: Oil, emulsifier, and co-emulsifier were selected as the carrier for the PESE formulation through a propolis-extract solubility test on each carrier, followed by evaluation of the nanoemulsion region in a pseudo ternary phase diagram. Pre-concentrate of PESE was prepared with the addition of 150 mg/mL propolis extract followed by characterization for the transmittance, globule size, zeta potential, thermodynamic stability, robustness to dilution, and accelerated stability. The selected formulation was tested for antibacterial activity using a microdilution method.

Results: The PESE characterization produced a clear nanoemulsion with a globule size ranging from 13 to 45 nm and zeta potential of less than −38 mV. The PESE formulation with a composition of 150 mg/mL propolis extract, 20% castor oil, 40%–70% Kolliphor EL, and 10%–40% polyethylene glycol (PEG) 400 were thermodynamically stable. The PESE formulation with the composition of 20% castor oil, 40% Kolliphor EL, and 40% PEG 400 was the optimum formulation that passed the robustness to dilution evaluation and an accelerated stability test for 3 months. The antibacterial activity test on this formulation indicated improved activity against Escherichia coli and Staphylococcus aureus compared with that of propolis extract.

Conclusion: These studies demonstrated that PESE in optimum formulation could be used as an antibacterial, particularly in E. coli and S. aureus.

In Silico studies of novel Sildenafil self-emulsifying drug delivery system absorption improvement for pulmonary arterial hypertension

Sildenafil is a potent selective inhibitor of phosphosdiesterase-5 previously used in erectile dysfunction and subsequently approved in 2005 for pulmonary arterial hypertension treatment. Since oral administration of sildenafil shows pharmacokinetic problems with mean absolute bioavailability of 41%, the goal of this work was to develop a novel sildenafil self-emulsifying drug delivery system (SEDDS) for oral absorption improvement and management of dosage. One pharmaceutical solution and four SEDDS containing sildenafil were successfully obtained and SEDDS formed O/W nanoemulsion with droplet size less than 300 nm. The stability studies evidenced that the SEDDS containing 3.3% w/w of sildenafil yielded the best results. The safety of 2-pyrrolidone/isobutanol in oral formulations was assessed in mice and no lethality was achieved in the placebo groups with LD50 of 490 mg/Kg for SEDDS II-3.3, suggesting it as a safe excipient for humans. Therewithal, in silico studies using PBPK models provided the pharmacokinetic profile of sildenafil SEDDS. Subsequently, in silico evaluation indicated that the sildenafil SEDDS droplet size influenced its bioavailability, enhancing absorption, assuring a good pharmacokinetic profile. These findings suggest that the formulations developed here presented the potential to enhance drug oral absorption with the possibility to control drug dosage as they are liquid pharmaceutical formulations.

Amelioration of lipophilic compounds in regards to bioavailability as self-emulsifying drug delivery system (SEDDS)

Background

High lipophilicity and poor aqueous solubility are the endemic problems of new drug molecules. Sixty to seventy percent of these drugs are unable to solubilize completely in aqueous media, or have very low permeability. This hampers their oral absorption and further leads to their poor bioavailability. Various researches are in progress to overcome these limitations. Novel technologies like nano-carrier systems have become popular for improving the solubility of drugs.

Main body

Lipid-based formulations, among nano systems, are taking pace for the enhancement of solubility, oral absorption, and hence the bioavailability of drugs. Among the lipid formulations, self-emulsification systems are gaining popularity by offering various advantages to delivery systems. Self-emulsifying drug delivery systems (SEDDS) are isotropic blends of oil and surfactant/co-surfactants. These ingredients upon gentle agitation in aqueous media results in the formation of o/w emulsion. In spite of many works published in SEDDS, the major concerns of this article are to discuss the various approaches to formulate a good lipid-based carrier system for poorly aqueous soluble drugs, role of various polymers, and their categories used in the formulation along-with the modern technologies used for enhancing the stability of liquid SEDDS. This review majorly focuses upon the problems related to the poor aqueous solubility of the newer lipid molecules and the solutions to overcome their solubility and in addition bioavailability.

Conclusion

As per the researches done in formulation and optimization of SEDDS for the enhancement of bioavailability of lipophilic molecules, it can be stated that the aqueous solubility as well as bioavailability can be increased by many folds compared to their marketed or other oral formulations.

Self-Emulsifying Drug Delivery System of Celecoxib for Avoiding Delayed Oral Absorption in Rats with Impaired Gastric Motility

This study aimed to develop a self-emulsifying drug delivery system (SEDDS) of celecoxib (CEL) for suppressed delay in oral absorption under impaired gastric motility. A pseudo-ternary phase diagram was constructed for the determination of the optimal component ratio in SEDDS of CEL (SEDDS/CEL), and the SEDDS/CEL was physicochemically characterized. A pharmacokinetic study on orally dosed CEL samples (5-mg CEL/kg) was carried out in normal and propantheline (PPT)-treated rats to mimic impaired gastric motility. SEDDS/CEL rapidly formed a fine emulsion with a mean size of 147 nm in distilled water and significantly improved the dissolution behavior of CEL under pH 1.2 condition with a 20-fold higher dissolved amount than crystalline CEL. In normal rats, orally dosed SEDDS/CEL provided a 4.6-fold higher systemic exposure than that of crystalline CEL, due to the improved dissolution properties of CEL. Crystalline CEL showed delayed and decreased oral absorption of CEL in PPT-treated rats as evidenced by a 6.9-h-delayed mean absorption time and only 12% of the systemic exposure of CEL compared with those in normal rats. In contrast, SEDDS/CEL enhanced the oral absorption of CEL with a 14.6-fold higher systemic exposure with significant suppression of delay in absorption than crystalline CEL even in PPT-treated rats. SEDDS/CEL could be an efficacious option for suppressing delay in CEL absorption even under impairment of gastric motility, possibly leading to rapid and reproducible management of severe acute pain.

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.

Development of Topical/Transdermal Self-Emulsifying Drug Delivery Systems, Not as Simple as Expected

Self-emulsifying drug delivery systems (SEDDSs) originated as an oral lipid-based drug delivery system with the sole purpose of improving delivery of highly lipophilic drugs. However, the revolutionary drug delivery possibilities presented by these uniquely simplified systems in terms of muco-adhesiveness and zeta-potential changing capacity lead the way forward to ground-breaking research. Contrarily, SEDDSs destined for topical/transdermal drug delivery have received limited attention. Therefore, this review is focused at utilising principles, established during development of oral SEDDSs, and tailoring them to fit evaluation strategies for an optimised topical/transdermal drug delivery vehicle. This includes a detailed discussion of how the authentic pseudo-ternary phase diagram is employed to predict phase behaviour to find the self-emulsification region most suitable for formulating topical/transdermal SEDDSs. Additionally, special attention is given to the manner of characterising oral SEDDSs compared to topical/transdermal SEDDSs, since absorption within the gastrointestinal tract and the multi-layered nature of the skin are two completely diverse drug delivery territories. Despite the advantages of the topical/transdermal drug administration route, certain challenges such as the relatively undiscovered field of skin metabolomics as well as the obstacles of choosing excipients wisely to establish skin penetration enhancement might prevail. Therefore, development of topical/transdermal SEDDSs might be more complicated than expected.