Enhanced Percutaneous Permeability of Diclofenac Using a New U-Type Dilutable Microemulsion

Quality by Design (QbD) Approach for a Nanoparticulate Imiquimod Formulation as an Investigational Medicinal Product

The present article exemplifies the application of the concept of quality by design (QbD) for the systematic development of a nanoparticulate imiquimod (IMQ) emulsion gel formulation as an investigational medicinal product (IMP) for evaluation in an academic phase-I/II clinical trial for the treatment of actinic keratosis (AK) against the comparator Aldara (EudraCT: 2015-002203-28). The design of the QbD elements of a quality target product profile (QTPP) enables the identification of the critical quality attributes (CQAs) of the drug product as the content of IMQ, the particle-size distribution, the pH, the rheological properties, the permeation rate and the chemical, physical and microbiological stability. Critical material attributes (CMAs) and critical process parameters (CPPs) are identified by using a risk-based approach in an Ishikawa diagram and in a risk-estimation matrix. In this study, the identified CPPs of the wet media ball-milling process's milling time and milling speed are evaluated in a central composite design of experiments (DoEs) approach, revealing criticality for both factors for the resulting mean particle size, while only the milling time is significantly affecting the polydispersity. To achieve a mean particle size in the range of 300-400 nm with a minimal PdI, the optimal process conditions are found to be 650 rpm for 135 min. Validating the model reveals a good correlation between the predicted and observed values. Adequate control strategies were implemented for intermediate products as in-process controls (IPCs) and quality control (QC) tests of the identified CQAs. The IPC and QC data from 13 "IMI-Gel" batches manufactured in adherence to good manufacturing practice (GMP) reveal consistent quality with minimal batch-to-batch variability.

HLD-NAC design and evaluation of a fully dilutable lecithin-linker SMEDDS for ibuprofen

Lecithin-linker microemulsions have been previously proposed as a platform for designing a fully dilutable self-microemulsifying drug delivery system (SMEDDS). This SMEDDS formulation, composed of ethyl caprate (oil), lecithin (Le), glycerol monooleate (lipophilic linker, LL) and polyglycerol caprylate (hydrophilic linker, HL), produced a ternary phase diagram (TPD) that had a fully dilutable path suitable for oral drug delivery. However, introducing ibuprofen as an active pharmaceutical ingredient (API) resulted in TPD phase boundaries that eliminated the fully dilutable path. The purpose of this work was to understand the origin of the changes in the TPD, use that understanding to restore the fully dilutable path with an ibuprofen-loaded SMEDDS, and finally to evaluate the absorption of ibuprofen in vivo. The effect of ibuprofen on the HLD (hydrophilic-lipophilic difference, interpreted as normalized net interfacial curvature) of the system was evaluated via a polar oil model, showing that ibuprofen played a surfactant-like role, having a characteristic curvature (Cc) value of +5 (highly hydrophobic). The net-average curvature (NAC) framework used the HLD calculated with Le, LL, HL and ibuprofen Cc to generate TPDs in ibuprofen lecithin-linker systems. The HLD-NAC simulations show that restoring full dilutability required a highly hydrophilic linker (HL^-) with a Cc of -5 or more negative. The fully dilutable path was restored after introducing a hexaglycerol caprylate as HL- (Cc = -6). Plasma concentration profiles obtained with this ibuprofen-loaded SMEDDS showed a more than three-fold increase in the area under the curve (AUC) of rat plasma concentration profiles compared to the same 25 mg/kg ibuprofen dose in suspension.

Jojoba oil-based microemulsion for transdermal drug delivery

Background and purpose:

Microemulsions are gaining an increased interest in transdermal drug delivery. Microemulsions are stable, easy to prepare, and provide high solubilizing capacity for various drugs. The aim of this work was to prepare microemulsions from jojoba oil for transdermal delivery of ketorolac and lidocaine HCl with improved permeation.

Experimental approach:

Microemulsions based on jojoba oil as the oil phase were formulated for transdermal delivery of lidocaine HCl and ketorolac. Brij 97 was selected as surfactant and hexanol as cosurfactant. Pseudoternary phase diagrams were constructed. Selected microemulsion formulations were characterized for their physical properties and in vitro drug permeation.

Findings/Results:

Water-in-oil microemulsions were obtained with droplet sizes not more than 220 nm. The viscosity of the microemulsions was linked to the viscosity of the surfactant used. Improved drug permeation rates were observed for both model drugs. The significant increase in permeation rate in presence of hexanol was due to its impact on skin integrity as indicated by the histopathological study. Drug permeation enhancements were caused by the surfactant, the cosurfactant used, jojoba oil itself, and the microemulsion formulation. Higher surfactant content showed lower lag times and better flux.

Conclusion and implications:

Jojoba oil microemulsions are considered promising vehicles for transdermal delivery of ketorolac and lidocaine HCl with improved drug permeation. Jojoba oil-based microemulsion would present a safe and effective means for delivering drugs through the skin.

Incorporation of curcumin in liquid nanodomains embedded into polymeric films for dermal application

Liquid nanovehicles are gaining interest in drug delivery because of the high solubilization capacity of bioactives at their interface and enhanced permeation of compounds across physiological membranes. However, the dermal application of liquid nanovehicles is still limited. The goal of this research is to develop a dermal delivery system based on embedding of liquid nanovehicles into polymeric films, which will allow controlled release of the nanodroplets with the solubilized drug. In this study, we describe the incorporation of empty and curcumin-loaded nanodomains into polymeric film. The novel technology results in formation of homogeneous, transparent and elastic films with high (up to 85 wt%) loading capacity of nanodomains. The fundamental structural characterizations show that nanodomain structures embedded in the dry film are spontaneously reformed during the dermal application with similar droplets size of 10 nm. Ex-vivo release studies were performed on Franz diffusion cells and demonstrated a significant permeation of curcumin through the pig skin. This novel film technology can serve as a "solid platform reservoir" for liquid nanovehicles which enables controlled release of nanodroplets with solubilized bioactive.

Cocoa Pod Husk Pectin Intended as a Pharmaceutical Excipient Has No Adverse Effects on Haematological Parameters in Sprague Dawley Rats

Natural polymer research has recently become the focus of intensive research in the quest for new enabling excipients for novel drugs in pharmaceutical formulation for optimal treatment outcomes. Evaluations of some excipients have shown deleterious haematological effects of varying extents on the safety profile of these excipients. A 90-day subchronic toxicity study was conducted to evaluate the influence of cocoa pod husk (CPH) pectin on indicators for haematotoxicity. Male and female Sprague Dawley rats (SDRs) were fed with CPH pectin in doses up to 71.4 mg/kg. The effects of CPH pectin on the haematological indices, direct and total bilirubin, and the spleen were determined. The results indicated that CPH pectin did not induce any untoward toxic effects on the haematological indices, bilirubin levels, and the spleen. There were, however, elevations in MCV at day 30, which was not sustained after the 90 days. The data obtained from this study did not reveal any remarkable findings of toxicological relevance to the haematopoietic system.

Encapsulation of Antibiotic Levofloxacin in Biocompatible Microemulsion Formulation: Insights from Microstructure Analysis

Microemulsions (μEs) are unique systems that offer exciting perspectives in biophysical research for mimicing biomembranes at the molecular level. In the present study, biocompatible μE formulation of a new oil-in-water (o/w) system comprising clove oil/Tween 20/2-propanol/water was accomplished for encapsulating an antibiotic, levofloxacin (LVF). The pseudoternary phase diagram was delineated at a constant cosurfactant/surfactant (2:1) ratio to meet the economic feasibility. The gradual changes occurring in the microstructure of the as-formulated four-component μEs were explored via multiple complementary characterization techniques. The results of electrical conductivity (σ), viscosity (η), and optical microscopic measurements suggested the existence of a percolation transition to a bicontinuous structure in the microregions of the as-formulated μE. LVF displayed a high solubility (5.0 wt %) at the pH of 6.9 in an optimum μE formulation comprising 2-propanol (36.4%), Tween 20 (18.2%), clove oil (20.7%), and water (24.7%). The LVF-loaded μE composition showed long-term stability for over 6 months of storage. Fourier transform IR analysis showed that LVF was stable inside the μE formulation, indicating the absence of any possible aggregation of LVF. Dynamic light scattering revealed that the average particle size of drug-free μE (64.5 ± 3.4 nm) increases to 129.7 ± 5.8 nm upon loading of LVF, suggesting the accumulation of LVF in the interfacial layers of the micelles. Moreover, fluorescence measurements indicated that LVF might be localized in the interfacial film of μE system, which may result in a controlled release of drug.

Optimizing the dermal accumulation of a tazarotene microemulsion using skin deposition modeling

CONTEXT

It is well known that microemulsions are mainly utilized for their transdermal rather than their dermal drug delivery potential due to their low viscosity, and the presence of penetration enhancing surfactants and co-surfactants.

OBJECTIVE

Applying quality by design (QbD) principles, a tazarotene microemulsion formulation for local skin delivery was optimized by creating a control space.

MATERIALS AND METHODS

Critical formulation factors (CFF) were oil, surfactant/co-surfactant (SAA/CoS), and water percentages. Critical quality attributes (CQA) were globular size, microemulsion viscosity, tazarotene skin deposition, permeation, and local accumulation efficiency index.

RESULTS AND DISCUSSION

Increasing oil percentage increased globular size, while the opposite occurred regarding SAA/CoS, (p = 0.001). Microemulsion viscosity was reduced by increasing oil and water percentages (p < 0.05), due to the inherent high viscosity of the utilized SAA/CoS. Drug deposition in the skin was reduced by increasing SAA/CoS due to the increased hydrophilicity and viscosity of the system, but increased by increasing water due to hydration effect (p = 0.009). Models with very good fit were generated, predicting the effect of CFF on globular size, microemulsion viscosity, and drug deposition. A combination of 40% oil and 45% SAA/CoS showed the maximum drug deposition of 75.1%. Clinical skin irritation study showed that the aforementioned formula was safe for topical use.

CONCLUSION

This article suggests that applying QbD tools such as experimental design is an efficient tool for drug product design.

Overcoming the cutaneous barrier with microemulsions

Microemulsions are fluid and isotropic formulations that have been widely studied as delivery systems for a variety of routes, including the skin. In spite of what the name suggests, microemulsions are nanocarriers, and their use as topical delivery systems derives from their multiple advantages compared to other dermatological formulations, such as ease of preparation, thermodynamic stability and penetration-enhancing properties. Composition, charge and internal structure have been reported as determinant factors for the modulation of drug release and cutaneous and transdermal transport. This manuscript aims at reviewing how these and other characteristics affect delivery and make microemulsions appealing for topical and transdermal administration, as well as how they can be modulated during the formulation design to improve the potential and efficacy of the final system.

Probing the microstructure of nonionic microemulsions with ethyl oleate by viscosity, ROESY, DLS, SANS, and cyclic voltammetry

Microemulsions are important formulations in cosmetics and pharmaceutics and one peculiarity lies in the so-called "phase inversion" that takes place at a given water-to-oil concentration ratio and where the average curvature of the surfactant film is zero. In that context, we investigated the structural transitions occurring in Brij 96-based microemulsions with the cosmetic oil ethyl oleate and studied the influence of the short chain alcohol butanol on their structure and properties as a function of water addition. The characterization has been carried out by means of transport properties, spectroscopy, DLS, SANS, and electrochemical methods. The results confirm that the nonionic Brij 96 in combination with butanol as cosurfactant forms a U-type microemulsion that upon addition of water undergoes a continuous transition from swollen reverse micelles to oil-in-water (O/W) microemulsion via a bicontinuous region. After determining the structural transition through viscosity and surface tension, the 2D-ROESY studies give an insight into the microstructure, i.e., the oil component ethyl oleate mainly is located at the hydrophobic tails of surfactant while butanol molecules reside preferentially in the interface. SANS experiments show a continuous increase of the size of the structural units with increasing water content. The DLS results are more complex and show the presence of two relaxation modes in these microemulsions for low water content and a single diffusive mode only for the O/W microemulsion droplets. The fast relaxation reflects the size of the structural units while the slower one is attributed to the formation of a network of percolated microemulsion aggregates. Electrochemical studies using ferrocene have been carried out and successfully elucidated the structural transformations with the help of diffusion coefficients. An unusual behavior of ferrocene has been observed in the present microheterogeneous medium, giving a deeper insight into ferrocene electrochemistry. NMR-ROESY experiments give information regarding the internal organization of the microemulsion droplets. In general, one finds a continuous structural transition from a W/O over a bicontinuous to an O/W microemulsion, however with a peculiar network formation over an extended concentration range, which is attributed to the somewhat amphiphilic oil ethyl oleate. The detailed knowledge of the structural behavior of this type of system might be important for their future applications.

Nanocarrier for the transdermal delivery of an antiparkinsonian drug

The purpose of the present study was to investigate the potential of nanoemulsions as nanodrug carrier systems for the percutaneous delivery of ropinirole. Nanoemulsions comprised Capryol 90 as the oil phase, Tween 20 as the surfactant, Carbitol as the cosurfactant, and water as an external phase. The effects of composition of nanoemulsion, including the ratio of surfactant and cosurfactant (Smix) and their concentration on skin permeation, were evaluated. All the prepared nanoemulsions showed a significant increase in permeation parameters such as steady state flux (Jss) and permeability coefficient (Kp) when compared to the control (p<0.01). Nanoemulsion composition (NEL3) comprising ropinirole (0.5% w/w), Capryol 90 (5% w/w), Smix 2:1 (35% w/w), and water (59.5% w/w) showed the highest flux (51.81+/-5.03 microg/cm2/h) and was selected for formulation into nanoemulsion gel. The gel was further optimized with respect to oil concentration (Capryol 90), polymer concentration (Carbopol), and drug content by employing the Box-Behnken design, which statistically evaluated the effects of these components on ropinirole permeation. Oil and polymer concentrations were found to have a negative influence on permeation, while the drug content had a positive effect. Nanoemulsion gel showed a 7.5-fold increase in skin permeation rate when compared to the conventional hydrogel. In conclusion, the results of the present investigation suggested a promising role of nanoemulsions in enhancing the transdermal permeation of ropinirole.