Microemulsions as Solubilizers and Penetration Enhancers for Minoxidil Release from Gels

Skin penetration enhancers: Mechanistic understanding and their selection for formulation and design

The skin functions as a formidable barrier, particularly the stratum corneum, effectively restricting the penetration of most substances, including therapeutic agents. To circumvent this barrier, skin penetration enhancers (SPEs) are frequently employed to transiently increase skin permeability, facilitating drug absorption without causing irritation or damage. Despite advancements in dermal formulation development, a deeper understanding of the fundamental science underpinning drug delivery via SPEs remains essential. This review delivers a critical update on conventional SPEs, exploring their mechanisms in promoting drug permeation across the skin. In addition to offering an overview of percutaneous drug delivery, we examine the prevailing theories on how SPEs enhance drug transport. Furthermore, we address the intricate interplay between SPEs, drugs and the skin, providing valuable insights into how the molecular properties and permeation behaviours of SPEs influence their efficacy. This comprehensive review aims to support the ongoing development of optimised drug delivery systems for dermal applications by elucidating the complexities and challenges involved in using SPEs effectively.

In Situ Gelling Dexamethasone Oromucosal Formulation: Physical Characteristics Influencing Drug Delivery

The study focuses on the development of an in situ gelling dexamethasone (DEX) oromucosal formulation designed for the treatment of aphthous stomatitis. Three series of formulations were prepared; a first series containing DEX suspended, a second series containing DEX and, in addition, mint essential oil (EO), and a third series containing EO and DEX solubilized in propylene glycol (PG). In the composition, polymers in the role of mucoadhesive agent were interchanged (hydroxypropyl methylcellulose (HPMC), hydroxypropyl cellulose (HPC), hydroxyethyl cellulose (HEC), methyl cellulose (MC), carboxymethyl cellulose (CMC), and sodium carboxymethyl cellulose (NaCMC). Specifically, DEX was incorporated at a concentration of 0.1% (w/w) in each formulation. The influence of mint EO and DEX solubilization on the physical properties (pH measurements, rheological analysis, swelling ability, and texture analysis) and in vitro drug release was studied. Key findings revealed that HPMC-based formulation containing mint EO and PG exhibited best swelling properties (700 ± 46% after 5 h), adequate adhesiveness and in vitro drug release (34.7 ± 5.9%). Furthermore, the irritation potential assessed via the hen's egg test on the chorioallantoic membrane (HET-CAM) demonstrated low irritancy risk. Finally, Fourier-transform infrared spectroscopy (FT-IR) showed no incompatibility between DEX and excipients. Overall, the research highlights the potential of mucoadhesive systems in improving the therapeutic efficacy of oromucosal drug delivery for managing painful oral lesions.

Development and characterization of a self-nano emulsifying drug delivery system (SNEDDS) for Ornidazole to improve solubility and oral bioavailability of BCS class II drugs

This study aimed to investigate the in vitro performance of self-nanoemulsifying drug delivery systems (SNEDDSs) of Ornidazole (ORD), a poorly water-soluble drug. Self-nanoemulsifying drug delivery systems of ORD were prepared using various oils, non-ionic surfactants, and/or water-soluble co-solvents and assessed visually/by droplet size measurement. Equilibrium solubility of ORD in the anhydrous and diluted SNEDDS was conducted to achieve the maximum drug loading. The in vitro dissolution of SNEDDS was studied to compare the solubility of the representative formulations with API. The results from the characterization and solubility studies showed that SNEDDS formulations were stable with lower droplet sizes and showed higher ORD solubility. From the dissolution studies, it was found that the developed A7-SNEDDS formulation provided a significantly higher rate of ORD release (98.94 ± 0.68 in 1.0 h) compared to API. ORD-loaded SNEDDS formulations could be a potential oral pharmaceutical product with high drug-loading capacity, improved drug dissolution, and enhanced oral bioavailability.

Preparing a novel baicalin-loaded microemulsion-based gel for transdermal delivery and testing its anti-gout effect

We previously demonstrated that baicalin had efficacy against gouty arthritis (GA) by oral administration. In this paper, a novel baicalin-loaded microemulsion-based gel (B-MEG) was prepared and assessed for the transdermal delivery of baicalin against GA. The preparation method and transdermal capability of B-MEG was screened and optimized using the central composite design, Franz diffusion cell experiments, and the split-split plot design. Skin irritation tests were performed in guinea pigs. The anti-gout effects were evaluated using mice. The optimized B-MEG comprised of 50 % pH 7.4 phosphate buffered saline, 4.48 % ethyl oleate, 31.64 % tween 80, 13.88 % glycerin, 2 % borneol, 0.5 % clove oil and 0.5 % xanthan gum, with a baicalin content of (10.42 ± 0.08) mg/g and particle size of (15.71 ± 0.41) nm. After 12 h, the cumulative amount of baicalin permeated from B-MEG was (672.14 ± 44.11) μg·cm-2. No significant skin irritation was observed following B-MEG application. Compared to the model group, B-MEG groups significantly decreased the rate of auricular swelling (P < 0.01) and number of twists observed in mice (P < 0.01); and also reduced the rate of paw swelling (P < 0.01) and inflammatory cell infiltration in a mouse model of GA. In conclusion, B-MEG represents a promising transdermal carrier for baicalin delivery and can be used as a potential therapy for GA.

Solubility enhancement of fexofenadine using self-nano emulsifying drug delivery system for improved biomimetic attributes

BACKGROUND

Fexofenadine is a poorly water-soluble drug, which limit its bioavailability and ultimately therapeutic efficacy. Liquid self-nano emulsifying drug delivery system (L-SNEDDs) is an approach that can enhance the solubility of fexofenadine by increasing its surface area and reducing the particle size, which increases the rate and extent of drug dissolution.

METHOD

In this investigation, L-SNEDDs of fexofenadine was made up using surfactants and co-surfactant. The SNEDDS formulation was optimized using a pseudo-ternary phase diagram and characterized.

RESULTS

The optimized L-SNEDDS incorporated fexofenadine were thermodynamically stable and showed mean droplet size and zeta potential of 155nm and -18mV, respectively unaffected by the media pH. In addition, the viscosity, and refractive index were observed 18.4 and 1.49 cps, respectively for optimized L-SNEDDS fortified fexofenadine. The results of Fourier transform infrared spectroscopy revealed an insignificant interaction between the fexofenadine and excipients. A drug loading efficiency of 94.20% resulted with a complete in vitro drug release in 2h, compared with the pure drug, which demonstrate significant improvement in the efficacy. Moreover, these results signify that on further in vivo assessment L-SNEDDS fortified fexofenadine can indicate improvement in pharmacokinetic and clinical outcome.

CONCLUSION

Thus, the investigation revealed that, the L-SNEDDs incorporated fexofenadine was most effective with a mixture of surfactant and co-surfactant with improved solubility intend to relieve pain associated with inflammation with single-dose oral administration.

Glycols: The ubiquitous solvent for dermal formulations

Glycols stand out as one of the most commonly employed safe and effective excipients for pharmaceutical and cosmeceutical products. Their widespread adoption can be attributed to their exceptional solvency characteristics and their ability to interact effectively with skin lipids and keratin for permeation enhancement. Notably, propylene glycol enjoys significant popularity in this regard. Ongoing research endeavours have been dedicated to scrutinising the impact of glycols on dermal drug delivery and shedding light on the intricate mechanisms by which glycols enhance skin permeation. This review aims to mitigate the discordance within the existing literature, assemble a holistic understanding of the impact of glycols on the percutaneous absorption of active compounds and furnish the reader with a profound comprehension of the foundational facets pertaining to their skin permeation enhancement mechanisms, while simultaneously delving deeper into the intricacies of these processes.

Advancements in the Transdermal Drug Delivery Systems Utilizing Microemulsion-based Gels

Microemulsion gel, as a promising transdermal nanoparticle delivery system, addresses the limitations of microemulsions and enhances their performance in drug delivery and release. This article aims to discuss the advantages of microemulsion gel, including improved drug bioavailability, reduced drug irritation, enhanced drug penetration and skin adhesion, and increased antimicrobial properties. It explores the methods for selecting microemulsion formulations and the general processes of microemulsion preparation, as well as commonly used oil phases, surfactants, and co-surfactants. Additionally, the biomedical applications of microemulsion gel in treating conditions, such as acne and psoriasis, are also discussed. Overall, this article elucidates the significant potential of microemulsion gel in topical drug delivery, providing insights into future development and clinical applications.

Release of Tretinoin Solubilized in Microemulsion from Carbopol and Xanthan Gel: In Vitro versus Ex Vivo Permeation Study

BACKGROUND

Tretinoin (TRE) is, for its anti-comedogenic and comedolytic activity, widely used in the topical treatment of acne vulgaris. The effect lies in the regulation of sebum production and collagen synthesis. The study is devoted to the formulation of dermal gels containing TRE using microemulsion as the drug solubilizer.

METHODS

The aim was to evaluate the effect of the reference microemulsion (ME) and lecithin-containing microemulsion (ME_L) on the release of TRE through the synthetic membrane (in vitro) and the pig's ear skin (ex vivo) through the Franz cell diffusion method. Subsequently, after an ex vivo study, the amount of the drug in the skin influenced by the applied formulation was determined. In addition, the impact of ME on the microscopic structure, texture, and rheological properties of gels was evaluated.

RESULTS

On the basis of the analysis of texture, rheological properties, and drug release studies, Carbopol formulations appear to be more appropriate and stable. Considering the synthetic membrane as a stratum corneum, the Carbopol gel penetrated about 2.5-higher amounts of TRE compared to the Xanthan gel. In turn, ex vivo studies suggest that ME_L slows the drug transfer to the dissolution medium, simulating absorption into the blood, which is a desirable effect in local treatment. The drug retention study proved the highest amounts of TRE in the skin to which microemulsion-Carbopol formulations were applied.

CONCLUSION

The results confirm the benefit of TRE solubilization in ME due to its bioavailability from the tested dermal formulations.

Effect of Penetration Enhancers on Transdermal Delivery of Oxcarbazepine, an Antiepileptic Drug Using Microemulsions

Oxcarbazepine (OXC) is an anticonvulsant drug, indicated for the treatment of the neurological disorder, epilepsy. The objective of the present study was to evaluate the transdermal delivery of OXC from microemulsions using different penetration enhancers. Transcutol® P (TRC), oleic acid (OA), cineole (cin), Labrasol (LS), Tween 80 (T80) and N-Methyl-Pyrrolidone (NMP) were used as penetration enhancers as well as microemulsion components. Simple formulations of OXC in propylene glycol (PG) incorporating various penetration enhancers and combination of penetration enhancers were also evaluated for transdermal delivery. Drug delivery and penetration enhancement were studied using human cadaver skin on Franz diffusion cells. The results showed that all penetration enhancers improved the rate of permeation of OXC compared to the control. The flux of drug delivery from the various formulations was found to be, in decreasing order, cin > OA + TRC > NMP > TRC > OA. Overall, microemulsions prepared using cineole, Tween 80 and Transcutol® P (TRC) were shown to be provide the best penetration enhancement for OXC.

Nanoemulsion-Based Hydrogels and Organogels Containing Propolis and Dexpanthenol: Preparation, Characterization, and Comparative Evaluation of Stability, Antimicrobial, and Cytotoxic Properties

Recently, nanoemulsion-based gels have become very popular for dermal drug delivery, overcoming the disadvantages of conventional semi-solid drug forms. The aim of this study is to prepare and characterize nanoemulsion-based hydrogels and organogels containing combined propolis and dexpanthenol, and to compare their stability, antimicrobial, and cytotoxicity properties. Within the scope of characterization studies, organoleptic properties, drug content, morphology, pH, gel-sol conversion temperature, spreadability, viscosity, FT-IR, and release properties were evaluated in hydrogels and organogels. The characterization studies carried out were subjected to short-term stability evaluation at room temperature and refrigerator for 3 months. While no phase separation was observed in any of the formulations kept in the refrigerator, phase separation was observed in four formulations kept at room temperature. The release study successfully obtained an extended release for propolis and dexpanthenol. In the antimicrobial susceptibility study, Hydrogel 1 showed activity against S. aureus, while Organogel 1 showed activity against both S. aureus and S. epidermidis. In the cytotoxicity study against HDFa cells, both Hydrogel 1 and Organogel 1 were found to be nontoxic at low doses. These hydrogels and organogels, which contain propolis and dexpanthenol in combination for the first time, are promising systems that can be used in wound and burn models in the future.

Lecithins: A comprehensive review of their properties and their use in formulating microemulsions

Lecithins are a phospholipid-rich mixture recovered from the degumming process of crude vegetable oils. Since the nineteenth century, this by-product of oil processing has been used as a food and pharmaceutical ingredient. Lecithins' popularity as an ingredient in the pharmaceutical and food industries arises from their particular properties, such as their hydrophilic-lipophilic balance, critical micellar concentration, and assembly properties. However, there is limited knowledge of the use of lecithins to formulate pharmaceutical- and food-grade microemulsions. Unlike conventional emulsions, microemulsions are thermodynamically stable systems that offer long-term stability. Besides, microemulsions show nano-sized droplets, transparency, ease of preparation and scale-up, and do not require expensive equipment. This review aims to provide a comprehensive overview of lecithins, their properties, and their use in formulating microemulsions, a promising method to incorporate, protect, and deliver bioactive compounds in pharmaceutical and food products. PRACTICAL APPLICATIONS: Lecithins are a phospholipid-rich mixture recovered from the degumming process of crude vegetable oils. Since the nineteenth century, this by-product of oil processing has been used as a food ingredient. Lecithin phospholipids are commonly used as emulsifier agents in the food and pharmaceutical industries because of their particular properties. However, there is limited knowledge of the use of lecithins to formulate pharmaceutical- or food-grade microemulsions. Unlike conventional emulsions, microemulsions are stable systems that offer long-term stability, nano-sized droplets, transparency, ease of preparation and scale-up, and do not require expensive equipment. This review aims to provide a comprehensive overview of lecithins, their properties, and their use in formulating microemulsions, a promising method to incorporate, protect, and deliver bioactive compounds such as vitamins, flavors, antioxidants, nutrients, colors, antimicrobials, and polyphenols.

Comparative Study of Polysaccharide-Based Hydrogels: Rheological and Texture Properties and Ibuprofen Release

Polysaccharides are attractive gelling agents in pharmacy due to their safety, biocompatibility, biodegradability, relatively easy way of preparation, and low price. Due to their variable physical-chemical properties, polysaccharides have potentialities to be used for designing new drug delivery systems for controlled drug release. In this comparative study, rheological and texture properties as well as the in vitro release of model drug ibuprofen (IBU) with 11 polysaccharide-based hydrogels were investigated. The in vitro release of IBU significantly differed between (i) neutral (hydroxy/alkylcelluloses), (ii) anionic (carboxyalkylcellulose and its sodium salt, tragacanth, carrageenan, xanthan gum), and (iii) cationic (chitosans) hydrogels due to different contribution of provided interactions and viscosity within the hydrogel groups. The drug release kinetics of each hydrogel system was evaluated for five kinetic models. Several combinations of cationic hydrogels with neutral or anionic ones were performed to illustrate possibilities of providing modified IBU release profiles. In this context, chitosan was presented as an effective modifier of diffusion profiles for negatively charged drugs formulated into combined polymeric systems, providing their prolonged release. The most appropriate hydrogel for the topical application (i.e., providing favorable rheological and texture properties along with the highest drug release) was selected from a studied series of polysaccharide-based hydrogels.

Insights from a Box-Behnken Optimization Study of Microemulsions with Salicylic Acid for Acne Therapy

The present study brings to attention a method to develop salicylic acid-based oil in water (O/W) microemulsions using a tensioactive system based on Tween 80, lecithin, and propylene glycol (PG), enriched with a vegetable oat oil phase and hyaluronic acid. The systems were physically characterized and the Quality by design approach was applied to optimize the attributes of microemulsions using Box-Behnken modeling, combined with response surface methodology. For this purpose, a 33 fractional factorial design was selected. The effect of independent variables namely X1: Tween 80/PG (%), X2: Lecithin (%), X3: Oil phase (%) was analyzed considering their impact upon the internal structure and evaluated parameters chosen as dependent factors: viscosity, mean droplet size, and work of adhesion. A high viscosity, a low droplet size, an adequate wettability-with a reduced mechanical work-and clarity were considered as desirable for the optimal systems. It was found that the optimal microemulsion which complied with the established conditions was based on: Tween 80/PG 40%, lecithin 0.3%, oat oil 2%, salicylic acid 0.5%, hyaluronic acid 1%, and water 56.2%. The response surface methodology was considered an appropriate tool to explain the impact of formulation factors on the physical properties of microemulsions, offering a complex pattern in the assessment of stability and quality attributes for the optimized formulation.

Ten Years of Knowledge of Nano-Carrier Based Drug Delivery Systems in Ophthalmology: Current Evidence, Challenges, and Future Prospective

The complex drug delivery barrier in the eye reduces the bioavailability of many drugs, resulting in poor therapeutic effects. It is necessary to investigate new drugs through appropriate delivery routes and vehicles. Nanotechnology has utilized various nano-carriers to develop potential ocular drug delivery techniques that interact with the ocular mucosa, prolong the retention time of drugs in the eye, and increase permeability. Additionally, nano-carriers such as liposomes, nanoparticles, nano-suspensions, nano-micelles, and nano-emulsions have grown in popularity as an effective theranostic application to combat different microbial superbugs. In this review, we summarize the nano-carrier based drug delivery system developments over the last decade, particularly review the biology, methodology, approaches, and clinical applications of nano-carrier based drug delivery system in the field of ocular therapeutics. Furthermore, this review addresses upcoming challenges, and provides an outlook on potential future trends of nano-carrier-based drug delivery approaches in ophthalmology, and hopes to eventually provide successful applications for treating ocular diseases.