Ropivacaine loaded microemulsion and microemulsion-based gel for transdermal delivery: Preparation, optimization, and evaluation

Tailoring moxifloxacin hydrochloride loaded oleic acid liposomes for the topical management of Methicillin-Resistant Staphylococcus aureus (MRSA)- Induced skin infection: In-vitro characterization and in-vivo assessment

Oleic acid liposomes (OALs) are novel vesicular carriers ofunsaturated fatty acids and their corresponding ionized species, arranged within an enclosed lipid bilayer. This study aimed to encapsulate moxifloxacin HCl (MOX), a broad-spectrum antibacterial drug into OALs for effective treatment of Methicillin-resistant Staphylococcus aureus (MRSA) infection through topical application. Various OALs were formulatedby combining varied quantities of phosphatidylcholine (PC), oleic acid (OA), and cholesterol (CH) with 50 mg of MOX. The OALs were produced utilizing varying sonication durations. MOX-loaded OALs were formulated using the thin film hydration method by applying (24) a full factorial design utilizing the Design-Expert® software. The formula for MOX-loaded OALs was OAL13, which consisted of 200 mg of PC and 20 mg of OA. The mixture was sonicated for 5 min. The OAL13 exhibited spherical vesicles with a small diameter and a smooth outer surface. Additionally, the entrapment efficiency was measured to be 75.00 ± 1.41 %, the particle size was 234.65 ± 4.74 nm, the polydispersity index was 0.53 ± 0.01, and the zeta potential was -38.50 ± 0.42 mV. The OAL13 formula exhibited an extended release profile. Moreover, the antibiofilm activity of OAL13 gel and MOX-loaded liposomes gel against MRSA infection demonstrates greater activity than the MOX gel at the maximum concentration used (MIC/2). Furthermore, the in-vivo study showed that OAL13 improved MOX's antimicrobial and immunomodulatory effects against MRSA infection by increasing TLR-2 and IL-1β, as well as their downstream molecules NF-κB and TNF-α. Moreover, the histopathological examination conducted by a skin irritation test has verified the safety of OAL13. Overall, the results demonstrated the significant efficacy of MOX-loaded OALs in the treatment of MRSA infected wounds when applied topically.

Enhancing Microemulsion-Based Therapeutic Drug Delivery: Exploring Surfactants, Co-Surfactants, and Quality-by-Design Strategies within Pseudoternary Phase Diagrams

Microemulsions (MEs) are homogeneous, isotropic, transparent, and thermodynamically stable mixtures of water, oil, and surfactants. Their unique properties have garnered increasing interest across various fields, including chemistry, pharmacology, biotechnology, and biology. This review aims to provide a comprehensive overview of ME compositions, their macroscopic appearances, and the roles of their essential components - oil, water, surfactant, and co-surfactant - in controlling the nature and stability of MEs. The review highlights the significance of MEs in drug delivery and other applications, highlighting their potential to enhance the solubility, stability, and bioavailability of active pharmaceutical ingredients (APIs). Key factors influencing ME formation, such as the types of surfactants, oils, water, temperature, and various additives, are thoroughly explored. The physicochemical properties of MEs, including small droplet size, large interfacial area, and solubilization capabilities for both hydrophilic and hydrophobic compounds, are discussed about their impact on biological behavior. The present work is an effort to discuss theories and phase diagrams crucial for ME formation, and the strategy of choosing appropriate surfactants and co-surfactants. and the advancements in the preparation and characterization techniques like the shift from visual inspection to advanced spectroscopic phase behavior studies. The work also describes the potential of MEs in drug delivery showcasing the most commonly used ME-based drug candidates as well as excipients highlighting how different excipients influence the release of active pharmaceutical ingredients and the way and quality-by-design approach has been utilized to optimize MEs, providing insights into the systematic design and development to achieve desired characteristics of ME formulations.

Contemplating Novel W/O Emulsion Based Gel for Anti-Psoriatic Activity of Tofacitinib in Imiquimod-Induced Balb/C Mice Model

Tyrosine kinase inhibitors like tofacitinib (TCB), are excellent examples of small molecular compounds that have demonstrated success in treating psoriasis. The current study aims to improve the efficacy of TCB and reduce its systemic adverse effects by developing a topical w/o emulgel formulation that will ameliorate the anti-psoriatic activity in a model of Imiquimod-induced BALB/c mice. In order to create w/o emulgel, the TCB was incorporated into the w/o emulsion using Peppermint oil, Transcutol P®, and PEG-200 followed by converted into a gel by adding Carbopol 940. The final formulation was optimized by applying a 3-level, 3-factor Box-Behnken Design (BBD). The optimized formulation showed a viscosity of 560606.6 ± 80.8 cps (560 Pa.S), and firmness of 356 ± 48 g, and that was within the acceptable range with respect to the marketed emulgel preparation available for topical application. The developed TCB-emulgel also exhibited a controlled release profile, with 68.26 ± 8.33% release of TCB over 24 h and a 5-fold greater skin permeation as compared to normal TCB-gel. Apart from that, the application of TCB-emulgel on the diseased model results in a 3.3-times reduction in the PASI (Psoriasis Area Severity Index) scoring. Lastly, the epidermal reduction in histopathological evaluation, along with the reduction in TNF-α and Ki-67 levels observed in immunostaining, ensures the enhanced anti-psoriatic effect of the developed TCB-emulgel in comparison to the marketed product. To put it briefly, the findings of the study and the therapeutic effectiveness of the developed TCB-emulgel provide a strong basis for the clinical management of psoriasis in the future.

Advances in the use of local anesthetic extended-release systems in pain management

Pain management remains among the most common and largely unmet clinical problems today. Local anesthetics play an indispensable role in pain management. The main limitation of traditional local anesthetics is the limited duration of a single injection. To address this problem, catheters are often placed or combined with other drugs in clinical practice to increase the time that local anesthetics act. However, this method does not meet the needs of clinical analgesics. Therefore, many researchers have worked to develop local anesthetic extended-release types that can be administered in a single dose. In recent years, drug extended-release systems have emerged dramatically due to their long duration and efficacy, providing more possibilities for the application of local anesthetics. This paper summarizes the types of local anesthetic drug delivery systems and their clinical applications, discusses them in the context of relevant studies on local anesthetics, and provides a summary and outlook on the development of local anesthetic extended-release agents.

Formulation of Microemulsion-Based Gels for Enhanced Topical Administration of Nonsteroidal Anti-Inflammatory Drugs

Nonsteroidal anti-inflammatory drugs are commonly administered orally to manage pain and inflammation, but they can have negative gastrointestinal side effects. Topical delivery is an alternative, and microemulsions (μEs) have been shown to be effective in facilitating, but they suffer from a liquid nature and low long-term retention on the skin. Hence, microemulsified gels (μEGs) have been developed, and in this study, we explored certain μEGs with diclofenac sodium (DF-Na) and naproxen sodium (NP-Na) with the hypothesis to ensure a slower and more sustained delivery of NSAIDs through the skin. The μEGs comprised castor oil (∼8%), water (∼12%), Tween-20 (∼72%), Span-20 (∼8%), poloxamer 407, and DF-Na or NP-Na. Optical microscopy was used to study the microstructures in the μEs and μEGs, and phase transitions from water-in-oil (w/o) to oil-in-water (o/w) with continuous networks were observed. Based on studies with dynamic light scattering and analyses of electron micrographs, it was observed that the μEs and μEGs loaded with DF-Na and NP-Na comprised monomodal nanodroplets. The average sizes of the droplets were (∼35 nm) and (∼60 nm) for the μEGs, without and with drugs. Fluorescence spectroscopy was used to ensure that the drugs were more likely to be present in the hydrophobic microenvironment of the formulations. Moreover, ex vivo permeation studies were conducted at pH values of 5.5 and 7.4 across rabbit skin. The release rates of DF-Na (>99 ± 1.5%, P < 0.07) and NP-Na (>89 ± 1.1%, P < 0.01) were slower for the μEGs within 8-10 h than for the μEs at the low pH, which is of relevance to the optimal pH of the skin. It was observed that μEGs with high viscosities are effective and may have potential for use in topical drug delivery applications.

Preparation, process optimisation, stability and bacteriostatic assessment of composite nanoemulsion containing corosolic acid

Corosolic acid (CA), a pentacyclic triterpenoid, exhibits remarkably low hydrophilicity, restricting its application in aqueous systems. To enhance its hydrophilicity, we optimised nanoemulsion preparation conditions, resulting in a stable corosolic acid nanoemulsion system. By screening the oil phase, surfactant, and cosurfactant, along with investigating the mass ratio of surfactant and cosurfactant and the preparation temperature, we achieved an optimal corosolic acid nanoemulsion. We measured the particle size, polydispersity coefficient, and Zeta potential of the optimised formulation. The nanoemulsion's sustained-release effect, stability, and antibacterial activity were subsequently examined. The optimised formulation comprised ethyl oleate, cremophor EL, and Tween 80 (1.5:1), combined with ethanol in a ratio of 1:9:2.25 (w/w/w), and was prepared at 30 °C. This optimised corosolic acid nanoemulsion exhibited uniform particle size distribution, favourable dispersion, and notable slow-release capabilities. Importantly, the nanoemulsion demonstrated exceptional stability. In comparison to the positive control's bacteriostatic zone diameter, it was evident that the CA nanoemulsion (1.06 ± 0.11 mm) and blank nanoemulsion (1.03 ± 0.05 mm) both displayed notable inhibitory activity against S. aureus. Our findings established a solid foundation for the potential application of CA nanoemulsion in the food, cosmetics, and pharmaceutical industries. However, the application of CA nanoemulsion in real food or drug systems has not been explored yet.

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.

Acacetin-loaded microemulsion for transdermal delivery: preparation, optimization and evaluation

CONTEXT

Acacetin is reported as a potential drug candidate for the treatment of atrial fibrillation. However, clinical applications are limited by poor water solubility, limited ethanol solubility, and extremely low oral bioavailability.

OBJECTIVE

The present study prepared and evaluated acacetin-loaded microemulsion (ME) to achieve efficient pharmacokinetics together with no or minimal invasiveness for transdermal delivery.

MATERIALS AND METHODS

The formulation of ME was determined by the water titration method based on solubility results. The optimized formulation was achieved by the simplex lattice experiment design. The optimized ME formulations FA, FB and FC (FA with 10% and 50% DMSO as enhancers, respectively) were evaluated by ex vivo permeation with Franz diffusion cell and excised mice skin. In vivo pharmacokinetic studies were also performed at 8 mg/kg in rats within 6 h by transdermal administration.

RESULTS

The optimal ME (FA) was comprised of 12.2% caprylic acid decanoate monoditriglyceride (MCF-NF), 39.8% Smix (RH40: Trans = 2:1 w/w) and 48% water, respectively. Acacetin-loaded FA with particle size 36.0 ± 3.6 nm and drug solubility 803.7 ± 32.1 mg/g was prepared. FB had significantly higher cumulative amounts and higher AUC_0-∞ (196.6 ± 11.0 min × μg/mL, p < 0.05) than that FA alone (121.4 ± 33.1 min × μg/mL).

DISCUSSION AND CONCLUSIONS

The formulation of ME combined with the penetration enhancer can effectively improve the solubility and percutaneous absorption efficiency of acacetin, providing a new option for the non-invasive delivery of acacetin.

Synergistic approach for acne vulgaris treatment using glycerosomes loaded with lincomycin and lauric acid: Formulation, in silico, in vitro, LC-MS/MS skin deposition assay and in vivo evaluation

This study aims to develop a pharmaceutical formulation that combines the potent antibacterial effect of lincomycin and lauric acid against Cutibacterium acnes (C. acnes), a bacterium implicated in acne. The selection of lauric acid was based on an in silico study, which suggested that its interaction with specific protein targets of C. acnes may contribute to its synergistic antibacterial and anti-inflammatory effects. To achieve our aim, glycerosomes were fabricated with the incorporation of lauric acid as a main constituent of glycerosomes vesicular membrane along with cholesterol and phospholipon 90H, while lincomycin was entrapped within the aqueous cavities. Glycerol is expected to enhance the cutaneous absorption of the active moieties via hydrating the skin. Optimization of lincomycin-loaded glycerosomes (LM-GSs) was conducted using a mixed factorial experimental design. The optimized formulation; LM-GS4 composed of equal ratios of cholesterol:phospholipon90H:Lauric acid, demonstrated a size of 490 ± 17.5 nm, entrapment efficiency-values of 90 ± 1.4 % for lincomycin, and97 ± 0.2 % for lauric acid, and a surface charge of -30.2 ± 0.5mV. To facilitate its application on the skin, the optimized formulation was incorporated into a carbopol hydrogel. The formed hydrogel exhibited a pH value of 5.95 ± 0.03 characteristic of pH-balanced skincare and a shear-thinning non-Newtonian pseudoplastic flow. Skin deposition of lincomycin was assessed using an in-house developed and validated LC-MS/MS method employing gradient elution and electrospray ionization detection. Results revealed that LM-GS4 hydrogel exhibited a two-fold increase in skin deposition of lincomycin compared to lincomycin hydrogel, indicating improved skin penetration and sustained release. The synergistic healing effect of LM-GS4 was evidenced by a reduction in inflammation, bacterial load, and improved histopathological changes in an acne mouse model. In conclusion, the proposed formulation demonstrated promising potential as a topical treatment for acne. It effectively enhanced the cutaneous absorption of lincomycin, exhibited favorable physical properties, and synergistic antibacterial and healing effects. This study provides valuable insights for the development of an effective therapeutic approach for acne management.

Microemulsion-Based Keratin-Chitosan Gel for Improvement of Skin Permeation/Retention and Activity of Curcumin

Curcumin (Cur) is a kind of polyphenol with a variety of topical pharmacological properties including antioxidant, analgesic and anti-inflammatory activities. However, its low water solubility and poor skin bioavailability limit its effectiveness. In the current study, we aimed to develop microemulsion-based keratin-chitosan gel for the improvement of the topical activity of Cur. The curcumin-loaded microemulsion (CME) was formulated and then loaded into the keratin-chitosan (KCS) gel to form the CME-KCS gel. The formulated CME-KCS gel was evaluated for its characterization, in vitro release, in vitro skin permeation and in vivo activity. The results showed that the developed CME-KCS gel had an orange-yellow and gel-like appearance. The particle size and zeta potential of the CME-KCS gel were 186.45 ± 0.75 nm and 9.42 ± 0.86 mV, respectively. The CME-KCS gel showed desirable viscoelasticity, spreadability, bioadhesion and controlled drug release, which was suitable for topical application. The in vitro skin permeation and retention study showed that the CME-KCS gel had better in vitro skin penetration than the Cur solution and achieved maximum skin drug retention (3.75 ± 0.24 μg/cm²). In vivo experimental results confirmed that the CME-KCS gel was more effective than curcumin-loaded microemulsion (Cur-ME) in analgesic and anti-inflammatory activities. In addition, the CME-KCS gel did not cause any erythema or edema based on a mice skin irritation test. These findings indicated that the developed CME-KCS gel could improve the skin penetration and retention of Cur and could become a promising formulation for topical delivery to treat local diseases.

Exploring the Versatility of Microemulsions in Cutaneous Drug Delivery: Opportunities and Challenges

Microemulsions are novel drug delivery systems that have garnered significant attention in the pharmaceutical research field. These systems possess several desirable characteristics, such as transparency and thermodynamic stability, which make them suitable for delivering both hydrophilic and hydrophobic drugs. In this comprehensive review, we aim to explore different aspects related to the formulation, characterization, and applications of microemulsions, with a particular emphasis on their potential for cutaneous drug delivery. Microemulsions have shown great promise in overcoming bioavailability concerns and enabling sustained drug delivery. Thus, it is crucial to have a thorough understanding of their formulation and characterization in order to optimize their effectiveness and safety. This review will delve into the different types of microemulsions, their composition, and the factors that affect their stability. Furthermore, the potential of microemulsions as drug delivery systems for skin applications will be discussed. Overall, this review will provide valuable insights into the advantages of microemulsions as drug delivery systems and their potential for improving cutaneous drug delivery.

Potential of Lipid-Based Nanocarriers against Two Major Barriers to Drug Delivery-Skin and Blood-Brain Barrier

Over the past few years, pharmaceutical and biomedical areas have made the most astounding accomplishments in the field of medicine, diagnostics and drug delivery. Nanotechnology-based tools have played a major role in this. The implementation of this multifaceted nanotechnology concept encourages the advancement of innovative strategies and materials for improving patient compliance. The plausible usage of nanotechnology in drug delivery prompts an extension of lipid-based nanocarriers with a special reference to barriers such as the skin and blood-brain barrier (BBB) that have been discussed in the given manuscript. The limited permeability of these two intriguing biological barriers restricts the penetration of active moieties through the skin and brain, resulting in futile outcomes in several related ailments. Lipid-based nanocarriers provide a possible solution to this problem by facilitating the penetration of drugs across these obstacles, which leads to improvements in their effectiveness. A special emphasis in this review is placed on the composition, mechanism of penetration and recent applications of these carriers. It also includes recent research and the latest findings in the form of patents and clinical trials in this field. The presented data demonstrate the capability of these carriers as potential drug delivery systems across the skin (referred to as topical, dermal and transdermal delivery) as well as to the brain, which can be exploited further for the development of safe and efficacious products.

Science of, and insights into, thermodynamic principles for dermal formulations

Studies have demonstrated the significant role of the thermodynamic activity of drugs in skin drug delivery. This thermodynamic activity works as a driving force for increasing/improving the absorption of drugs by the skin. It can be changed according to the physicochemical parameters (e.g., solubility, partition coefficient, and water activity) of the drug in the vehicle. Thermodynamic principles have been used for the development of novel topical and transdermal delivery systems, demonstrating the importance of thermodynamic activity in enhancing drug permeation through the skin. In this review, we provide insights into thermodynamic principles and their roles in optimizing topical and transdermal drug delivery systems.

Preparation and Characterization of Lidocaine-Loaded, Microemulsion-Based Topical Gels

Microemulsion-based gels (MBGs) were prepared for transdermal delivery of lidocaine and evaluated for their potential for local anesthesia. Lidocaine solubility was measured in various oils, and phase diagrams were constructed to map the concentration range of oil, surfactant, cosurfactant, and water for oil-in-water (o/w) microemulsion (ME) domains, employing the water titration method at different surfactant/cosurfactant weight ratios. Refractive index, electrical conductivity, droplet size, zeta potential, pH, viscosity, and stability of fluid o/w MEs were evaluated. Carbomer^® 940 was incorporated into the fluid drug-loaded MEs as a gelling agent. Microemulsion-based gels were characterized for spreadability, pH, viscosity, and in-vitro drug release measurements, and based on the results obtained, the best MBGs were selected and subsequently subjected to ex-vivo rat skin permeation anesthetic effect and irritation studies. Data indicated the formation of nano-sized droplets of MEs ranging from 20 - 52 nm with a polydispersity of less than 0.5. In-vitro release and ex-vivo permeation studies on MBGs showed significantly higher drug release and permeation in comparison to the marketed topical gel. Developed MBG formulations demonstrated greater potential for transdermal delivery of lidocaine and advantage over the commercially available gel product, and therefore, they may be considered as potential vehicles for the topical delivery of lidocaine.

Liposome and microemulsion loaded with ibuprofen: from preparation to mechanism of drug transport

To compare the difference between liposome (LP) and microemulsion (ME) in delivering ibuprofen (IBU) transdermally and explore relative mechanism. IBU-LP and IBU-ME were prepared by ethanol injection and spontaneous emulsification, respectively. The percutaneous delivery was evaluated using Franz diffusion cells. Fourier transform infra-red spectroscopy (FTIR), differential scanning calorimetry (DSC), activation energy (Ea), and confocal laser scanning microscopy (CLSM) were used to investigate the transdermal mechanism. The particle size and encapsulation efficiency were 228.00 ± 8.60 nm, 86.68 ± 1.43%(w/w) for IBU-LP, and 56.74 ± 7.11 nm, 91.08 ± 3.27%(w/w) for IBU-ME. Percutaneous study showed that formulations enhanced permeation and drug retention in the skin. FTIR and DSC showed that the permeation occurred due to the interaction of the formulations with the lipid bilayer and the protein. The decrease in Ea (1.506 and 0.939 kcal/mol) revealed that the stratum corneum (SC) lipid bilayers were significantly disrupted and this destructive effect of IBU-LP was stronger. IBU-LP was superior to IBU-ME in the aspects of transdermal delivery of IBU.

In vitro and in vivo evaluation of cinnamaldehyde Microemulsion-Mucus interaction

The current investigation explores the possible mechanism of the microemulsion drug delivery system to improve the oral bioavailability of cinnamaldehyde (CA), an important food spice, from the perspective of the microemulsion-mucus system. The cinnamaldehyde microemulsion (CA-ME) was prepared by the water titration method combined with the pseudo-ternary phase diagram. The dynamic analysis was applied to detect the drug release in vitro. An intestinal mucosal injury test was conducted to evaluate the safety of CA-ME and drug absorption across the intestinal tract of rats was investigated through an Ussing chamber system. The rheology of blank mucus and drug-loaded mucus was investigated using a rheometer. The bioavailability of CA-ME in rats was evaluated through pharmacokinetic characteristics. The ratio of optimal prescription was Tween 80: 1,2-propanediol: vitamin E oil: CA: water = 24.3:4.8:5:7.5:58.4. The droplets were uniform in size and evenly dispersed. Rheological studies showed that the microemulsion-mucus system all exhibit pseudoplastic fluid behavior, and CA-ME increased the viscosity of the mucus to a certain extent. Compared with CA solution, CA-ME promoted the absorption of CA in various intestinal segments, especially the ileum. Pharmacokinetic experiments showed that the relative bioavailability of CA-ME was enhanced 2.5-fold higher than that of CA solution. ME as a carrier for lipophobic substances, may increase the viscosity of the intestine mucus system to obtain longer residue time and better absorption. PRACTICAL APPLICATIONS: In this study, in vitro absorption Ussing model was combined with rheological and pharmacokinetic analysis to systematically analyze the intestinal mucus mechanism of microemulsion to improve the oral bioavailability of cinnamic aldehyde. It laid the foundation for exploring the absorption and transport of drugs in the intestinal mucus barrier.

Dual Delivery of Fluticasone Propionate and Levocetirizine Dihydrochloride for the Management of Atopic Dermatitis Using a Microemulsion-Based Topical Gel

The current study investigates the potential for topical delivery of a fluticasone propionate (FP) and levocetirizine dihydrochloride (CTZ)-loaded microemulsion (ME) for the management of atopic dermatitis. Various microemulsion components were chosen based on their solubility and emulsification capabilities, and the ternary phase diagram was constructed. A total of 12 microemulsion formulations were screened for various attributes like vesicle size, polydispersity index, ζ-potential, percent transmittance, density, and pH. The average globule size and ζ-potential of FP and levocetirizine-containing ME were 52.12 nm and -2.98 ζ-potential, respectively. Transmission electron microscopy confirmed the spherical nature of the globules. The developed system not only controlled the release of both drugs but also enhanced the efficacy of the drugs on a rodent model. Histopathological studies confirmed the safety of the developed system. The present findings provide evidence for a scalable and simpler approach for the management of atopic dermatitis.

Intranasal delivery of Clozapine using nanoemulsion-based in-situ gels: An approach for bioavailability enhancement

Limited solubility and hepatic first-pass metabolism are the main causes of low bioavailability of anti-schizophrenic drug, Clozapine (CZP). The objective of the study was to develop and validate nanoemulsion (NE) based in-situ gel of CZP for intranasal administration as an approach for bioavailability enhancement. Solubility of CZP was initially investigated in different oils, surfactants and co-surfactants, then pseudoternary phase diagrams were constructed to select the optimized ratio of oil, surfactant and co-surfactant. Clear and transparent NE formulations were characterized in terms of droplet size, viscosity, solubilization capacity, transmission electron microscopy, in-vitro drug release and compatibility studies. Selected NEs were incorporated into different in-situ gel bases using combination of two thermosensitive polymers; Pluronic® F-127 (PF127) and F-68 (PF68). NE-based gels (NG) were investigated for gelation temperature, viscosity, gel strength, spreadability and stability. Moreover, selected NGs were evaluated for ex-vivo permeation, mucoadhesive strength and nasal ciliotoxicity. Peppermint oil, tween 80 and transcutol P were chosen for NE preparation owing to their maximum CZP solubilization. Clear NE points extrapolated from tween 80:transcutol P (1:1) phase diagram and passed dispersibility and stability tests, demonstrated globule size of 67.99 to 354.96 nm and zeta potential of −12.4 to −3.11 mV with enhanced in-vitro CZP release (>90% in some formulations). After incorporation of the selected N3 and N9 formulations of oil:Smix of 1:7 and 2:7, respectively to a mixture of PF127 and PF68 (20:2% w/w), the resultant NG formulations exhibited optimum gelation temperature and viscosity with enhanced CZP permeation and retention through sheep nasal mucosa. Ciliotoxicity examinations of the optimum NGs displayed no inflammation or damage of the lining epithelium and the underlying cells of the nasal mucosa. In conclusion, NE-based gels may be a promising dosage form of CZP for schizophrenia treatment.

Microemulsified Gel Formulations for Topical Delivery of Clotrimazole: Structural and In Vitro Evaluation

Microemulsified gels (μEGs) with fascinating functions have become indispensable as topical drug delivery systems due to their structural flexibility, high stability, and facile manufacturing process. Topical administration is an attractive alternative to traditional methods because of advantages such as noninvasive administration, bypassing first-pass metabolism, and improving patient compliance. In this article, we report on the new formulations of microemulsion-based gels suitable for topical pharmaceutical applications using biocompatible and ecological ingredients. For this, two biocompatible μE formulations comprising clove oil/Brij-35/water/ethanol (formulation A) and clove oil/Brij-35/water/1-propanol (formulation B) were developed to encapsulate and improve the load of an antimycotic drug, Clotrimazole (CTZ), and further gelatinized to control the release of CTZ through skin barriers. By delimiting the pseudo-ternary phase diagram, optimum μE formulations with clove oil (∼15%) and Brij-35 (∼30%) were developed, keeping constant surfactant/co-surfactant ratio (1:1), to upheld 2.0 wt % CTZ. The as-developed formulations were further converted into smart gels by adding 2.0 wt % carboxymethyl cellulose (CMC) as a cross-linker to adhere to the controlled release of CTZ through complex skin barriers. Electron micrographs show a fine, monodispersed collection of CTZ-μE nanodroplets (∼60 nm), which did not coalesce even after gelation, forming spherical CTZ-μEG (∼90 nm). However, the maturity of CTZ nanodroplets observed by dynamic light scattering suggests the affinity of CTZ for the nonpolar microenvironment, which was further supported by the peak-to-peak correlation of Fourier transform infrared (FTIR) analysis and fluorescence measurement. In addition, HPLC analysis showed that the in vitro permeation release of CTZ-μEG from rabbit skin in the ethanolic phosphate buffer (pH = 7.4) was significantly increased by >98% within 6.0 h. This indicates the sustained release of CTZ in μEBG and the improvement in transdermal therapeutic efficacy of CTZ over its traditional topical formulations.

Development of a novel cannabinoid-loaded microemulsion towards an improved stability and transdermal delivery

The aim of this study was to develop a stable microemulsion (ME) for transdermal delivery of tetrahydrocannabinolic acid (THCA) and cannabidiolic acid (CBDA). The lipid-based vehicles were selected by screening cannabinoid solubility and the emulsifying ability of surfactants. Pseudo-ternary phase diagrams were constructed by formulation of cannabinoids with Capryol® 90 as oil phase, Tween® 80, Solutol® HS15, Procetyl® AWS, and Cremophor® RH40 as surfactants, ethanol as cosurfactant, and distilled water as the aqueous phase. A significant improvement in transmembrane flux (J_ss), permeability coefficient (K_p), and enhancement ratio (E_R) was found in one system compared to other formulations. This ME consisted of 1.0% (w/w) of cannabinoids, 5% (w/w) of Capryol® 90, 44% (w/w) S_mix (2:1, Procetyl® AWS and Ethanol) and 50.0% (w/w) of distilled water. Additionally, the effects of pH on the permeation of the cannabinoids were investigated. Based on the pH value THCA and CBDA-loaded ME exhibited the highest permeation at pH 5.17 and pH 5.25. After storing the pH-adjusted P2 ME and the optimized P2 ME for 180 days at 4℃ and 25℃, the content of cannabinoids was over 95%. Consequently, the cannabinoid-loaded ME system is a promising option for solubilizing and stabilizing lipophilic drugs like cannabinoids and utilize them for transdermal delivery.

Microemulsion-Based Media in Nose-to-Brain Drug Delivery

Nose-to-brain drug delivery has recently attracted enormous attention as an alternative to other delivery routes, including the most popular oral one. Due to the unique anatomical features of the nasal cavity, drugs administered intranasally can be delivered directly to the central nervous system. The most important advantage of this approach is the ability to avoid the blood-brain barrier surrounding the brain and blocking the entry of exogenous substances to the central nervous system. Moreover, selective brain targeting could possibly avoid peripheral side effects of pharmacotherapy. The challenges associated with nose-to-brain drug delivery are mostly due to the small volume of the nasal cavity and insufficient drug absorption from nasal mucosa. These issues could be minimized by using a properly designed drug carrier. Microemulsions as potential drug delivery systems offer good solubilizing properties and the ability to enhance drug permeation through biological membranes. The aim of this review is to summarize the current status of the research focused on microemulsion-based systems for nose-to-brain delivery with special attention to the most extensively investigated neurological and psychiatric conditions, such as neurodegenerative diseases, epilepsy, and schizophrenia.

Development of Nanoemulsion-based Hydrogel Containing Andrographolide: Physical Properties and Stability Evaluation

Introduction:

Andrographolide is a compound that shows various pharmacological activities, which can be applied topically or orally. Nanoemulsion can improve drug solubility and stability, but has limitations for topical application. Incorporation of nanoemulsion into hydrogel can increase the viscosity of the system which can prolong the drug residence time. The aim of this study was to develop andrographolide nanoemulsion-based hydrogel for topical application.

Method:

Andrographolide nanoemulsion was prepared using Capryol 90 as the oil, Kolliphor RH 40 as the surfactant, and propylene glycol as the cosurfactant. Droplet size and polydispersity index of the nanoemulsions were evaluated using particle size analyzer. D-optimal mixture design was employed to generate the total number of runs (formulation), and obtain the optimum formulation. Fourteen formulations of nanoemulsion-based hydrogel were prepared by incorporating nanoemulsion into the hydrogel base (1:1). Carbopol was employed as the gelling agent, whereas other excipients including propylene glycol, oleic acid, triethanolamine, methylparaben, and propylparaben were also added to produce hydrogel base. Nanoemulsion-based hydrogel was evaluated for its pH, viscosity, and physical appearance (after 8 weeks of storage).

Results:

The result revealed that nanoemulsion-based hydrogel containing 34.65% of carbopol, 1.35% of triethanolamine, and 9% of propylene glycol was selected as an optimum formulation which shows acceptable pH, viscosity, and physical appearance. This optimum nanoemulsion-based hydrogel has pH of 6.50 ± 0.02, and 2492.33 ± 36.91 cP of viscosity with milky white color, and smooth homogeneous texture.

Conclusion:

This study suggested that andrographolide can be successfully formulated into an acceptable nanoemulsion-based hydrogel.

Formulation and Evaluation of Novel Hybridized Nanovesicles for Enhancing Buccal Delivery of Ciclopirox Olamine

Ciclopirox olamine (CPO) is a topical wide-spectrum antimycotic agent that possesses antifungal, antibacterial and anti-inflammatory activities. Loading CPO into a hybridized vesicular system is expected to enhance its buccal permeation and hence, therapeutic activity, whereas the frequent administration and side effects are reduced. Vesicular systems with high penetration ability were prepared based on cholesterol, Lipoid S45 or Phospholipon 90H, with span 60 while incorporating a penetration enhancer (Labrafac or labrasol) followed by full assessment of their size, entrapment efficiency, and drug release profiles. The optimum formulation, composed of Lipoid S45 and Labrafac, possessed the smallest vesicle size (346.1 nm), highest entrapment efficiency (94.4%), and sustained CPO release pattern, and was characterized for its morphology and thermal properties. This powerful mixture of the penetration enhancers (Lipoid S45 and Labrafac) in the designed hybridized vesicles was thoroughly investigated for their characteristics after being incorporated in bioadhesive gel. Moreover, enhanced antifungal activity was demonstrated either upon testing the designed formulation on agar plates or in vivo upon treating infected rabbits with the proposed formulation. Results suggest that the presented bioadhesive gel incorporating the CPO-loaded vesicles can be a promising delivery system that can offer a prolonged localized antifungal treatment with enhanced therapeutic effect.

3,5,4'-Trimethoxy-trans-stilbene loaded microemulsion for cutaneous melanoma therapy by transdermal drug delivery

For therapy of skin cancer, transdermal administration has been a potential way to enhance chemotherapy. However, the drug delivery efficacy remained unsatisfactory because of the physiological barriers from the skin to the tumor, which hindered the effect of 3,5,4'-trimethoxy-trans-stilbene (BTM), a drug that has toxicity to cancer. Herein, we prepared an oil-in-water (O/W) microemulsion to load BTM (BTM-ME) for transdermal therapy of melanoma. BTM-ME was characterized by size, zeta potential, and polymer disperse index (PDI). B16F10 melanoma cell line was used for cell experiments and animal models. And cell uptake, viability assay, and flow cytometry were to test the cell internalization and the ability of BTM-ME to induce cancer cell apoptosis. Skin penetration testing was to detect its penetration efficiency to the skin. And tumor-bearing mice were used to prove the improvement of anti-cancer efficacy of BTM-ME with the combination of Taxol. BTM was successfully loaded in O/W microemulsion, with a drug loading capacity of 24.82 mg/mL. BTM-ME can penetrate the skin and increase the retention of BTM in the epidermis. And the combination of Taxol and BTM-ME effectively suppressed tumor growth and has lower toxicity to normal organs. BTM-ME provides adjuvant therapy to cutaneous melanoma and the combination of Taxol and BTM-ME has the clinical potential for skin cancer therapy. Graphical abstract.

Comparison of ropivacaine combined with sufentanil for epidural anesthesia and spinal-epidural anesthesia in labor analgesia

BACKGROUND

To compare the application and efficacy of ropivacaine combined with sufentanil for continuous epidural anesthesia (CEA) and combined spinal-epidural anesthesia (CSEA) in labor analgesia.

METHODS

Three hundred sixty pregnant women requesting labor analgesia from October 2017 to August 2018 were selected retrospectively. According to the anesthetic method, subjects were divided into CSEA group and CEA group. Ropivacaine combined with sufentanil were used in all subjects. The labor time, visual analogue scale (VAS), Apgar score of newborn, adverse pregnancy outcomes and adverse drug reactions were observed.

RESULTS

There was no significant difference in pre-analgesia (T₀) VAS scores between the two groups (P > 0.05). VAS scores of first stage of labor (T₁), second stage of labor (T₂) and third stage of labor (T₃) in CSEA group were significantly lower than CEA group (P < 0.01). The onset time, T₁ and total labor time in CSEA group were significantly shorter than CEA group (P < 0.01). There were no significant differences between T2 and T3 (P > 0.05). There were no significant differences in adverse pregnancy outcomes and Apgar scores at 1, 5 and 10 min after birth between the two groups (P > 0.05). The incidence of adverse drug outcomes in CSEA group was significantly lower than CEA group (P < 0.01). Maternal satisfaction in CSEA group was significantly higher than CEA group (P < 0.01).

CONCLUSION

Considering ropivacaine combined with sufentanil for CSEA achieved a shorter onset time and labor period, significant analgesic effect, lower adverse drug reactions rates and higher subject satisfaction than CEA, it may be worthy of clinical promotion and application.

Self-microemulsifying oral fast dissolving films of vitamin D3 for infants: Preparation and characterization

Combining the advantages of self-microemulsifying technology and oral fast dissolving technology, a self-microemulsifying oral fast dissolving films (SMEOFDF) of vitamin D3 was developed in this study. The pseudoternary phase diagram of microemulsion was constructed using water titration method, and the formulation of films was optimized by orthogonal experimental design. The prepared SMEOFDF of vitamin D3 was a thin film, in which the liquid drops of self-microemulsion were embedded. It had good mechanical properties (thickness 166.7 ± 3.30 µm, tensile strength 38.45 ± 3.72 MPa, elongation 23.38 ± 4.23%, and folding endurance >200 times), and its disintegration time was about 18 ± 1.23 s. After being redissolved in water, microemulsion could form spontaneously, with particle size of 181.2 nm and zeta potential of 16.1 mV. The release profile of vitamin D from SMEOFDF could be well described by first-order equation.

Lipid-based carriers for the delivery of local anesthetics

INTRODUCTION

There is a clinical need for pharmaceutical dosage forms devised to prolong the acting time of local anesthetic (LA) agents or to reduce their toxicity. Encapsulation of LA in drug delivery systems (DDSs) can provide long-term anesthesia for inpatients (e.g. in immediate postsurgical pain control, avoiding the side effects from systemic analgesia) and diminished systemic toxicity for outpatients (in ambulatory/dentistry procedures). The lipid-based formulations described here, such as liposomes, microemulsions, and lipid nanoparticles, have provided several nanotechnological advances and therapeutic alternatives despite some inherent limitations associated with the fabrication processes, costs, and preclinical evaluation models.

AREAS COVERED

A description of the currently promising lipid-based carriers, including liposomes, microemulsions, and nanostructured lipid carriers, followed by a systematic review of the existing lipid-based formulations proposed for LA. Trends in the research of these LA-in-DDS are then exposed, from the point of view of administration route and alternatives for non-traditionally administered LA molecules.

EXPERT OPINION

Considering the current state and potential future developments in the field, we discuss the reasons for why dozens of formulations published every year fail to reach clinical trials; only one lipid-based formulation for the delivery of local anesthetic (Exparel®) has been approved so far.

Topical delivery of 3,5,4'-trimethoxy-trans-stilbene-loaded microemulsion-based hydrogel for the treatment of osteoarthritis in a rabbit model

The aim of this study was to develop a microemulsion-based hydrogel (MBH) formulation of 3,5,4'-trimethoxy-trans-stilbene (BTM) as topical delivery system for the treatment of osteoarthritis (OA). The pseudo-ternary phase diagrams were constructed to optimize the microemulsion (ME) formulation. The ME formulation containing 18.8% Cremopher EL35 (surfactant), 9.4% Transcutol HP (co-surfactant), 3.1% LABRAFIL M 1944 CS (oil), and 68.7% water was selected. The obtained BTM-loaded ME (BTM-ME) had a spherical morphology (17.5 ± 1.4 nm), with polydispersity index (PDI) value of 0.068 ± 0.016 and zeta potential of - 11.8 ± 0.5 mV, and was converted into BTM-loaded MBH (BTM-MBH) using Carbopol 940. Ex vivo skin permeation study showed that both ME and MBH formulations significantly enhanced the amount of BTM permeated. The cumulative amount of BTM permeated after 12 h (Q₁₂) for ME, and MBH formulations were 3.25- and 1.96-fold higher than that for emulsion gel (EG). Pharmacokinetic study showed that the AUC of BTM suspension (oral) was three times higher than that of BTM-MBH (topical). Topical delivery of BTM-MBH demonstrated remarkable anti-OA effect in a rabbit model of OA induced by papain, with decreased levels of pro-inflammatory cytokines. The developed MBH formulation might be a promising strategy for topical delivery of BTM for treatment of OA.

Lipid nanoparticles loading triptolide for transdermal delivery: mechanisms of penetration enhancement and transport properties

Background

In recent years, nanoparticles (NPs) including nanostructured lipid carries (NLC) and solid lipid nanoparticles (SLN) captured an increasing amount of attention in the field of transdermal drug delivery system. However, the mechanisms of penetration enhancement and transdermal transport properties of NPs are not fully understood. Therefore, this work applied different platforms to evaluate the interactions between skin and NPs loading triptolide (TPL, TPL-NLC and TPL-SLN). Besides, NPs labeled with fluorescence probe were tracked after administration to investigate the dynamic penetration process in skin and skin cells. In addition, ELISA assay was applied to verify the in vitro anti-inflammatory effect of TPL-NPs.

Results

Compared with the control group, TPL-NPs could disorder skin structure, increase keratin enthalpy and reduce the SC infrared absorption peak area. Besides, the work found that NPs labeled with fluorescence probe accumulated in hair follicles and distributed throughout the skin after 1 h of administration and were taken into HaCaT cells cytoplasm by transcytosis. Additionally, TPL-NLC could effectively inhibit the expression of IL-4, IL-6, IL-8, IFN-γ, and MCP-1 in HaCaT cells, while TPL-SLN and TPL solution can only inhibit the expression of IL-6.

Conclusions

TPL-NLC and TPL-SLN could penetrate into skin in a time-dependent manner and the penetration is done by changing the structure, thermodynamic properties and components of the SC. Furthermore, the significant anti-inflammatory effect of TPL-NPs indicated that nanoparticles containing NLC and SLN could serve as safe prospective agents for transdermal drug delivery system.

Development of microemulsions of suitable viscosity for cyclosporine skin delivery

Psoriasis is a widespread chronic disease affecting 2-4% of the population in Western countries. Its mild-to-moderate form, representing approximately 80% of the total cases, is treated by topical application, with corticosteroid being the standard treatment. However, in case of psoriasis, no single treatment works for every patient and optimizing topical therapy is a key aspect. A possible alternative is represented by cyclosporine, an immunosuppressant cyclic peptide administered orally in the treatment of the severe form. Its topical application could avoid the problems related to systemic immunosuppression, but the unfavourable physico-chemical properties (MW: 1202 Da; LogP ≈ 3) hinder its permeation across the stratum corneum. The aim of the paper was the preparation, characterization and ex-vivo evaluation of cyclosporine loaded microemulsions using oleic acid as oil phase, either Tween^®80 or a soluble derivative of vitamin E (TPGS) as surfactants and either Transcutol^®, propylene glycol or 1,3 propanediol as co-surfactants. The issue of formulation viscosity was also addressed 1) by evaluating the thickening of Tween^®80-based microemulsions by direct addition of different rheological modifiers, 2) by building pseudo-ternary phase diagrams using TPGS, to identify the water/oil/surfactants proportions resulting in viscous self-gelifying systems. Nine formulations (five Tween^®80-based and four TPGS-based) were selected, characterized in terms of droplets size (low viscosity systems) or rheological properties (high viscosity systems), loaded with 6 mg/g cyclosporine and applied ex-vivo on porcine skin for 22 h. A relevant skin accumulation was obtained either with a low-viscosity Tween^®80-based microemulsion (9.78 ± 3.86 µg/cm²), or with a high viscosity TPGS-based microemulsion (18.3 ± 5.69 µg/cm²), with an increase of about 3 and 6 times respectively for comparison with a control cyclosporine solution in propylene glycol. The role of water content, surfactant, co-surfactant and viscosity was also addressed and discussed. The kinetic of skin uptake from the best performing formulation was finally evaluated, highlighting a relatively quick skin uptake and the achievement, after 2 h of contact, of potentially therapeutic cyclosporine skin concentrations.

Design and Development of Repaglinide Microemulsion Gel for Transdermal Delivery

Microemulsion formulation of repaglinide, a BCS class II hypoglycemic agent with limited oral bioavailability, was developed considering its solubility in various oils, surfactants, and cosurfactants. The pseudo-ternary phase diagrams for microemulsion regions were constructed by water titration method at K _m 1:1 and characterized for optical birefringence, percentage transmittance, pH, refractive index, globule size, zeta potential, viscosity, drug content, and thermodynamic stability. To enhance the drug permeation and residence time, the optimized microemulsions having mean globule size of 36.15 ± 9.89 nm was gelled with xanthan gum. The developed microemulsion-based gel was characterized for globule size, zeta potential, pH, and drug content. All evaluation parameters upon gelling were found to be satisfactory. Ex vivo permeability study across rat skin demonstrated higher steady-state flux (P < 0.05) for microemulsion of repaglinide in comparison to the repaglinide microemulsion gel. At the end of 24 h, the cumulative drug permeation from microemulsion and microemulsion gel was found to be 229.19 ± 24.34 and 180.84 ± 17.40 μg/cm², respectively. The microemulsion formulation showed 12.30-fold increase in flux as compared to drug suspension with highest enhancement ratio (E _r ) of 12.36. Whereas microemulsion gel exhibited 10.97-fold increase in flux (with highest E _r , 11.78) as compared to repaglinide (RPG) suspension. In vivo efficacy study was performed in normal Sprague-Dawley rats by using oral glucose tolerance test. Results of RPG transdermal microemulsion gel demonstrated remarkable advantage over orally administered RPG by reducing the glucose level in controlled manner. Hence, it could be a new, alternative dosage form for effective therapy of type 2 diabetes mellitus.

Design, Development, and Optimization of Dexibuprofen Microemulsion Based Transdermal Reservoir Patches for Controlled Drug Delivery

The aim of the study was to develop a reservoir-type transdermal patch for a controlled delivery of dexibuprofen and to evaluate its in vivo anti-inflammatory activity in Albino Wistar rats. In order to develop these patches, six formulations of dexibuprofen microemulsion comprising ethyl oleate, Tween 80: PG (2 : 1), and water were prepared by simplex lattice design and characterized. The reservoir compartment was filled with these microemulsions and in vitro release and skin permeation were assessed. The optimized patch was obtained on the basis of the responses: Q₂₄ and flux. The impact of drug loading, surface area, membrane thickness, adhesive, and agitation speed on drug release and permeation was also studied. The skin sensitivity reaction and in vivo anti-inflammatory activity of optimized patch were evaluated. Stability study at three different temperatures for three months was carried out. The result suggests that a membrane based patch with zero-order release rate, Q₂₄ of 79.13 ± 3.08%, and maximum flux of 331.17 µg/cm²h can be obtained exhibiting suitable anti-inflammatory activity with no visible skin sensitivity reaction. The outcomes of stability study recommend storage of patches at 4°C having shelf-life of 6.14 months. The study demonstrates that the reservoir-type transdermal patch of dexibuprofen microemulsion has a potential of delivering drug across skin in controlled manner with required anti-inflammatory activity.

Potential of Non-aqueous Microemulsions to Improve the Delivery of Lipophilic Drugs to the Skin

In this study, non-aqueous microemulsions were developed because of the challenges associated with finding pharmaceutically acceptable solvents for topical delivery of drugs sparingly soluble in water. The formulation irritation potential and ability to modulate the penetration of lipophilic compounds (progesterone, α-tocopherol, and lycopene) of interest for topical treatment/prevention of skin disorders were evaluated and compared to solutions and aqueous microemulsions of similar composition. The microemulsions (ME) were developed with BRIJ, vitamin E-TPGS, and ethanol as surfactant-co-surfactant blend and tributyrin, isopropyl myristate, and oleic acid as oil phase. As polar phase, propylene glycol (MEPG) or water (MEW) was used (26% w/w). The microemulsions were isotropic and based on viscosity and conductivity assessment, bicontinuous. Compared to drug solutions in lipophilic vehicles, MEPG improved drug delivery into viable skin layers by 2.5-38-fold; the magnitude of penetration enhancement mediated by MEPG into viable skin increased with drug lipophilicity, even though the absolute amount of drug delivered decreased. Delivery of progesterone and tocopherol, but not lycopene (the most lipophilic compound), increased up to 2.5-fold with MEW, and higher amounts of these two drugs were released from MEW (2-2.5-fold). Both microemulsions were considered safe for topical application, but MEPG-mediated decrease in the viability of reconstructed epidermis was more pronounced, suggesting its higher potential for irritation. We conclude that MEPG is a safe and suitable nanocarrier to deliver a variety of lipophilic drugs into viable skin layers, but the use of MEW might be more advantageous for drugs in the lower range of lipophilicity.

Preparation and evaluation of microemulsion‑based transdermal delivery of Cistanche tubulosa phenylethanoid glycosides

The primary aim of the present study was to develop a novel microemulsion (ME) formulation to deliver phenylethanoid glycoside (PG) for use in skin lighteners and sunscreens. The oil phase was selected on the basis of drug solubility, while the surfactant and cosurfactant were screened and selected on the basis of their solubilizing capacity and the efficiency with which they formed MEs. Pseudoternary phase diagrams were constructed to evaluate ME regions and five formulations of oil-in-water MEs were selected as vehicles. In vitro skin permeation experiments were performed to optimize the ME formulation and to evaluate its permeability in comparison to that of saline solution. The physicochemical properties of the optimized ME and the permeating ability of PG delivered by this ME were also investigated. The optimized ME formulation was composed of isopropyl myristate (7%, w/w), Cremorphor EL (21%, w/w), propylene glycol (7%, w/w) and water (65%, w/w). The cumulative amount of PG that permeated through excised mouse skin when carried by ME was ~1.68 times that when PG was carried by saline solution only. The cumulative amount of PG in the microemulsion (4149.650±37.3 µg·cm⁻²) was significantly greater than that of PG in the saline solution (2288.63±20.9 µg·cm⁻²). Furthermore, the permeability coefficient indicated that optimized microemulsion was a more efficient carrier for transdermal delivery of PG than the control solution (8.87±0.49 cm/hx10⁻³ vs. 5.41±0.12 cm/hx10⁻³). Taken together, the permeating ability of ME-carried PG was significantly increased compared with saline solution.