Developing Cream Formulations: Renewed Interest in an Old Problem

Microfluidics-on-a-chip for designing celecoxib-based amorphous solid dispersions: when the process shapes the product

The fundamental idea underlying the use of amorphous solid dispersions (ASDs) is to make the most of the solubility advantage of the amorphous form of a drug. However, the drug stability becomes compromised due to the higher free energy and disorder of molecular packing in the amorphous phase, leading to crystallization. Polymers are used as a matrix to form a stable homogeneous amorphous system to overcome the stability concern. The present work aims to design ASD-based formulations under the umbrella of quality by design principles for improving oral drug bioavailability, using celecoxib (CXB) as a model drug. ASDs were prepared from selected polymers and tested both individually and in combinations, using various manufacturing techniques: high-shear homogenization, high-pressure homogenization, microfluidics-on-a-chip, and spray drying. The resulting dispersions were further optimized, resorting to a 32 full-factorial design, considering the drug:polymers ratio and the total solid content as variables. The formulated products were evaluated regarding analytical centrifugation and the influence of the different polymers on the intrinsic dissolution rate of the CXB-ASDs. Microfluidics-on-a-chip led to the amorphous status of the formulation. The in vitro evaluation demonstrated a remarkable 26-fold enhancement in the intrinsic dissolution rate, and the translation of this formulation into tablets as the final dosage form is consistent with the observed performance enhancement. These findings are supported by ex vivo assays, which exhibited a two-fold increase in permeability compared to pure CXB. This study tackles the bioavailability hurdles encountered with diverse active compounds, offering insights into the development of more effective drug delivery platforms.

Enhancing topical delivery of ISRIB: Optimizing cream formulations with chemical enhancers and pH adjustment

Chemical warfare agents, particularly vesicants like lewisite, pose a threat due to their ability to cause skin damage through accidental exposure or deliberate attacks. Lewisite rapidly penetrates the skin, causing inflammation and blistering. This study focuses on developing a cream formulation of a therapeutic agent, called integrated stress response inhibitor (ISRIB), to treat lewisite-induced injuries. Moreover, animal studies demonstrate a molecular target engagement (ISR) and significant efficacy of ISRIB against lewisite-induced cutaneous injury. The goal of this formulation is to enhance the delivery of ISRIB directly to affected skin areas using an oil-in-water cream emulsion system. We investigated various excipients, including oils, surfactants, emollients, and permeation enhancers, to optimize ISRIB's solubility and penetration through the skin. The result of this study indicated that the optimal formulation includes 30 % w/w of N-Methyl-2-pyrrolidone, dimethyl sulfoxide and Azone® at a pH of 5. 5. It delivered the highest amount of ISRIB into the skin, demonstrating highest skin absorption with no detectable systemic exposure. Additionally, characterization of the cream, including texture analysis, emulsion type, and content uniformity, confirmed its' suitability for topical application. These findings suggest that ISRIB cream formulation is a promising approach for the localized treatment of skin injuries caused by lewisite.

Decoding Cosmetic Complexities: A Comprehensive Guide to Matrix Composition and Pretreatment Technology

Despite advancements in analytical technologies, the complex nature of cosmetic matrices, coupled with the presence of diverse and trace unauthorized additives, hinders the application of these technologies in cosmetics analysis. This not only impedes effective regulation of cosmetics but also leads to the continual infiltration of illegal products into the market, posing serious health risks to consumers. The establishment of cosmetic regulations is often based on extensive scientific experiments, resulting in a certain degree of latency. Therefore, timely advancement in laboratory research is crucial to ensure the timely update and adaptability of regulations. A comprehensive understanding of the composition of cosmetic matrices and their pretreatment technologies is vital for enhancing the efficiency and accuracy of cosmetic detection. Drawing upon the China National Medical Products Administration's 2021 Cosmetic Classification Rules and Classification Catalogue, we streamline the wide array of cosmetics into four principal categories based on the following compositions: emulsified, liquid, powdered, and wax-based cosmetics. In this review, the characteristics, compositional elements, and physicochemical properties inherent to each category, as well as an extensive overview of the evolution of pretreatment methods for different categories, will be explored. Our objective is to provide a clear and comprehensive guide, equipping researchers with profound insights into the core compositions and pretreatment methods of cosmetics, which will in turn advance cosmetic analysis and improve detection and regulatory approaches in the industry.

Rheology of Complex Topical Formulations: An Analytical Quality by Design Approach to Method Optimization and Validation

Analytical method validation ensures that a method provides trustworthy information about a particular sample when applied in accordance with the predefined protocol. According to regulatory standards, the rheological characteristics of topically applied semisolid formulations are one of the key elements involved in microstructure equivalence documentation. Therefore, for generic drug product manufacturers, it is a dire need to take a step forward in rheology method development and validation procedures. This paper aims to apply Analytical Quality by Design (AQbD) principles towards the development and validation of rheology methods for topical creams, as complex semisolid formulations. Risk assessment was carried out through an Ishikawa diagram and an estimate failure mode, effects, and criticality analysis (FMECA). Sample application, peltier temperature control, and sample rest time were identified as critical method variables (CMVs), and a 2³ full factorial design was applied to understand their impact on rotational, creep recovery and, oscillatory measurements. The development of the method was carried out as per the ICH Q8-Q10, and Q14 guidelines and validated according to ICH Q2 (R2) guideline. The method demonstrated adequate precision (RSD < 15%), as well as selectivity. AQbD provided a comprehensive framework for developing a reliable and effective rheology method for this type of formulation.

Prevention of skin lesions caused by the use of protective face masks by an innovative gelatin-based hydrogel patch: design and in vitro studies

The recent Covid-19 pandemics led to the increased use of facial masks, which can cause skin lesions due to continuous pressure, tension and friction forces on the skin. A preventive approach is the inclusion of dressings between the face and the mask. However, there are still uncertainties about the protective effect of dressings and whether their use compromises the efficiency of masks. The current study aimed to develop and test the efficacy of a gelatin-based hydrogel patch to be placed between the mask and the facial area. Design of Experiment with a Quality by Design approach tools were used in the patch development and in vitro characterization was performed through rheological evaluation, ATR-FTIR and molecular docking studies. Furthermore, tribology studies were performed to test the patch performance. The results showed that the addition of excipients enhanced gelation temperature, elasticity and adhesiveness parameters. The interactions between excipients were confirmed by ATR-FTIR and molecular docking. The tribology assay revealed similar friction values at room and physiological temperature, and when testing different skin types. In conclusion, the physical properties and the performance evaluation reported in this study indicate that this innovative film-forming system can be used to prevent skin lesions caused by the continuous use of protective masks.

In vitro characterization and clinical evaluation of skin hydration by two formulations mimicking the skin's natural components

BACKGROUND

We have developed innovative base formulations that were designed to mimic the skin with respect to its components and galenic structure. Components include water, proteins, lipids, sugars and minerals.

OBJECTIVES

We characterized formulations and their skin penetration using in vitro methods and evaluated their impact on skin hydration in a clinical trial.

METHODS

Scanning electron microscopy (SEM) imaging and X-ray diffraction were used to analyse formulations as well as formulation impact on the stratum corneum (SC) structure. Mass spectrometry imaging (MSI) was used to compare formulation ingredients with SC components and to detect their distribution in the skin. Clinical studies were performed to confirm effects on skin hydration and investigate potential adverse skin effects (irritation and sensitization).

RESULTS

SEM and X-ray diffraction of the formulations showed that lipids were organized in sheets similar to SC lipids. MSI demonstrated similarities between formulation components and skin constituents, as well as a good penetration into the skin. The formulations did not modify the lamellar organization of the SC lipids, but they increased the relative proportion of the crystallized lipids and some of the amorphous lipids. In in vivo studies, a high level of hydration was maintained over 24 h after application with an intense and 'very good hydration'. Both formulations were shown to be non-(photo)sensitizers with excellent tolerance. Sensorial evaluation indicated the formulations were not oily or sticky and maintained the skin's suppleness over time. Formulations had a 'nude skin' touch and created a natural protective film.

CONCLUSIONS

The two formulations were well-tolerated and increased skin hydration in clinical subjects, an effect that could contribute to the alleviation of sensitive skin. The formulations were shown to resemble the lipid organization of the stratum corneum, as well as penetrate the skin without disrupting the lipid lamella organization.

Physical characterisation and stability study of formulated Chromolaena odorata gel

AIM

Formulating topical products for skin delivery has always been a challenge for pharmaceutical scientists to fulfil good formulation criteria. Despite the challenges, gel-based drug delivery offers some advantages such that it is non-invasive, painless, avoidance of the first-pass metabolism and has satisfactory patient compliance.

OBJECTIVES

In this study, Chromolaena odorata gel and quercetin gel (bioactive flavonoid compound) were successfully formulated and compared with placebo and conventional wound aid gel. The chromatographic profilling was conducted to screen the presence of phytoconstituents. Subsequently, all formulated gels were subjected to physical characteristic and stability study.

METHODS

Reverse Phase High-Performance Liquid Chromatography (RP-HPLC) of C.odorata methanolic leaves extract shows a distinct compound separation at retention time 8.4min to 34.8 min at 254nm. All gels were characterised by evaluating their rheological properties including storage modulus, loss modulus and plastic viscosity. Besides, texture analysis was performed to measure the gels' firmness, consistency, cohesiveness, and viscosity index.

RESULTS

From the observation, C. odorata gel demonstrated better spreadability as compared to the other gels, which acquired less work and favourable to be applied onto the skin. Moreover, C. odorata gel showed no changes in organoleptic properties and proven to be stable after 30 days of accelerated stability study at 40°C ± 2°C with relative humidity (RH) of 75%± 5%.

CONCLUSION

C. odorata gel has shown to be stable, reflecting the combination of materials used in the formulation, which did not degrade throughout the study. This work suggests the potential of this gel as a vehicle to deliver the active ingredients of C. odorata to the skin, which can be further explored as a topical application in antimicrobial wound management or other skin diseases study.

Complying with the Guideline for Quality and Equivalence for Topical Semisolid Products: The Case of Clotrimazole Cream

Semisolids constitute a significant proportion of topical pharmaceutical dosage forms available on the market, with creams being considered profitable systems for releasing active substances into the skin. This work aimed at the development of a generic Clotrimazole topical cream, based on the assumptions that assist the development of such formulations. First, the critical parameters to obtain a final formulation as similar as possible to the reference product were defined. Then, the percentages of cetyl palmitate and octyldodecanol were identified as critical variables and chosen for optimization in further studies. A "quality by design" approach was then used to identify the effect of process variability on the structural and functional similarity (Q3) of the generic product qualitatively (Q1) and quantitatively (Q2). A two-factor central composite orthogonal design was applied and eleven different formulations were developed and subjected to physicochemical characterization and product performance studies. The results were used to estimate the influence of the two variables in the variation of the responses, and to determine the optimum point of the tested factors, using a design space approach. Finally, an optimized formulation was obtained and analysed in parallel with the reference. The obtained results agreed with the prediction of the chemometric analysis, validating the reliability of the developed multivariate models. The in vitro release and permeation results were similar for the reference and the generic formulations, supporting the importance of interplaying microstructure properties with product performance and stability. Lastly, based on quality targets and response constraints, optimal working conditions were successfully achieved.

Effects of processing conditions and glycerol concentration on rheological and texture properties of starch-based hydrogels produced by high pressure processing (HPP)

Starch-based hydrogels are natural polymeric structures which could be potentially utilized in food, pharma and cosmetic sectors to produce creams, gels and ointments, as well as functional foods and products for personalized nutrition. In this paper, the effects of processing conditions (pressure levels and holding time) on gelation of corn and rice starch solutions were evaluated also in presence of glycerol. Considering the utmost importance of humectants as active moisturizers in gels, their addition in starch solutions has been investigated in view of the industrial exploitation of HPP starch-based hydrogels. Experimental results demonstrated that at 600 MPa the gelation of the formulations tested was homogenous and the hydrogels formed were stable. However, glycerol at 10% concentration played an antagonistic role, being longer processing times necessary to form gels. Viscosity and G' values of rice and corn starch HPP hydrogels decreased with increasing glycerol concentration, particularly for corn starch hydrogels. At all HPP processing conditions investigated, rice starch solutions containing the humectant were more prone to gelation and the hydrogels formed had better texture properties than those based on corn starch. 5% glycerol concentration was identified as the critical value to obtain stable HPP hydrogels with good rheological and texture properties.

Rheology by Design: A Regulatory Tutorial for Analytical Method Validation

The increasing demand for product and process understanding as an active pursuit in the quality guideline Q8 and, more recently, on the draft guideline on quality and equivalence of topical products, has unveiled the tremendous potential of rheology methods as a tool for microstructure characterization of topical semisolid dosage forms. Accordingly, procedure standardization is a dire need. This work aimed at developing and validating a methodology tutorial for rheology analysis. A 1% hydrocortisone cream was used as model cream formulation. Through a risk assessment analysis, the impact of selected critical method variables (geometry, temperature and application mode) was estimated in a broad range of rheological critical analytical attributes-zero-shear viscosity, upper-shear thinning viscosity, lower-shear thinning viscosity, infinite-shear viscosity, rotational yield point, thixotropic relative area, linear viscoelastic region, oscillatory yield point, storage modulus, loss modulus, and loss tangent. The proposed validation of the approach included the rheometer qualification, followed by the validation of numerous operational critical parameters regarding a rheology profile acquisition. The thixotropic relative area, oscillatory yield point, flow point and viscosity related endpoints proved to be highly sensitive and discriminatory parameters. This rationale provided a standard framework for the development of a reliable and robust rheology profile acquisition.

Progressing Towards the Sustainable Development of Cream Formulations

This work aims at providing the assumptions to assist the sustainable development of cream formulations. Specifically, it envisions to rationalize and predict the effect of formulation and process variability on a 1% hydrocortisone cream quality profile, interplaying microstructure properties with product performance and stability. This tripartite analysis was supported by a Quality by Design approach, considering a three-factor, three-level Box-Behnken design. Critical material attributes and process parameters were identified from a failure mode, effects, and criticality analysis. The impact of glycerol monostearate amount, isopropyl myristate amount, and homogenization rate on relevant quality attributes was estimated crosswise. The significant variability in product droplet size, viscosity, thixotropic behavior, and viscoelastic properties demonstrated a noteworthy influence on hydrocortisone release profile (112 ± 2–196 ± 7 μg/cm²/√h) and permeation behavior (0.16 ± 0.03–0.97 ± 0.08 μg/cm²/h), and on the assay, instability index and creaming rate, with values ranging from 81.9 to 120.5%, 0.031 ± 0.012 to 0.28 ± 0.13 and from 0.009 ± 0.000 to 0.38 ± 0.07 μm/s, respectively. The release patterns were not straightforwardly correlated with the permeation behavior. Monitoring the microstructural parameters, through the balanced adjustment of formulation and process variables, is herein highlighted as the key enabler to predict cream performance and stability. Finally, based on quality targets and response constraints, optimal working conditions were successfully attained through the establishment of a design space.

Fast Screening Methods for the Analysis of Topical Drug Products

Considering the recent regulatory requirements, the overall importance of in vitro release testing (IVRT) methods regarding topical product development is undeniable, especially when addressing particulate systems. For each IVRT study, several hundreds of samples are generated. Therefore, developing rapid reversed-phase high-performance liquid chromatography (RP-HPLC) methods, able to provide a real-time drug analysis of IVRT samples, is a priority. In this study, eight topical complex drug products exhibiting distinct physicochemical profiles were considered. RP-HPLC methods were developed and fully validated. Chromatographic separations were achieved on a XBridgeTM C18 (5 µm particle size, 150 mm × 2.1 mm), or alternatively on a LiChrospher® 100 RP-18 (5 µm particle size, 125 mm × 4.6 mm) at 30 °C, under isocratic conditions using UV detection at specific wavelengths. According to the physicochemical characteristics of each drug, different mobile phases were selected. Irrespective of the drug (hydrocortisone, etofenamate, bifonazole, clotrimazole, acyclovir, tioconazole, clobetasol, and diclofenac) and formulation, retention time values did not exceed 6.5 min. All methods were linear, specific, precise, and accurate at the intraday and interday levels, robust, and stable. These were successfully applied to establish product-specific IVRT profiles, thus providing a key database useful for topical pharmaceutical manufacturers.