Rational Design of Topical Semi-Solid Dosage Forms-How Far Are We?

FORMULATION OF SEMI SOLID DOSAGE FORMS FOR TOPICAL APPLICATION UTILIZING QUALITY BY DESIGN (QbD) APPROACH

OBJECTIVE

Over the last few decades, there have been advancements in our comprehension of the design and development of topical semisolid formulations; however, they still follow an empirical development. Our study focuses on building a framework for designing and developing topical semisolid products using the "Quality-by-Design" (QbD) approach.

METHODS

A review of the literature was conducted to identify and list the factors related to the design and development of topical semi solid dosage forms using Quality by Design approach. The information extracted from the relevant articles was used to build a QbD framework based on four main pillars: Define the quality target product profile (QTPP); identify critical quality attributes (CQAs); identify critical material attributes (CMAs) and critical process parameters (CPPs); understand how CMAs and CPPs affect CQAs and establish a control strategy.

RESULTS

Some typical elements of the QTPP for topical products include dosage form, route of administration, shelf-life, critical quality attributes of the final formulation. Critical material attributes such as characteristics of API (molecular weight, lipophilicity, solubility, metamorphosis events, and polymorphism), characteristics of excipients, and critical process parameters (temperature, heating and cooling rates, mixing speed, pumping speed, order of addition) were identified and explained for their impact on CQAs.

CONCLUSIONS

Proper characterization of the API and drug delivery system will increase the likelihood of developing a stable, pleasing, and tolerable topical formulation and minimize the risk of failure.

Q1 and Q2 selection, Q3, IVRT, IVPT, pharmacokinetic and pharmacodynamic evaluation of topical generic product

OBJECTIVE

To establish a detailed step-by-step example for the topical development of generic products.

SIGNIFICANCE

Topical semisolids are complex products requiring extensive research for bioequivalence by establishing Q1/Q2/Q3.

METHODS

The detailed process establishes Q1/Q2 selection and Q3 evaluation of the innovator and proposed formulation. The proposed generic product along with the innovator formulation has been evaluated for physicochemical properties. Once the Q3 structure is matched with innovator formulation, the invitro release and in-vitro permeation study have been conducted to move forward for the bioequivalence study. Pharmacokinetic and pharmacodynamic studies were employed for bioequivalence with an innovator in humans.

RESULTS

Selection of Q1 and Q2 establish the formulation composition through literature search and reverse engineering. The test and reference products are pharmaceutically equivalent through Q3 characterization, IVRT, and IVPT. In the PK study, test and reference samples were compared for Cmax, Tmax, and t1/2 and found bioequivalent. The PD study was performed in pilot and pivotal study to establish dose duration response relationship and bioequivalence respectively without adverse events. A crucial study has exhibited that reference and test formulations are bioequivalent with a 90% confidence interval and results in 84.67%-101.09%.

CONCLUSION

The Cutivate® cream 0.05%, and proposed generic product Fluticasone Propionate cream 0.05% formulations are bioequivalent and have a favorable safety profile.

Advantages and therapeutic applications of different semisolids as vehicles for nano-based systems

The aim of this review is to highlight the role of semisolid systems as vehicles for nanovesicles and nanoparticles. In general, nanotechnology plays a critical role in facilitating the delivery of therapeutic agents to their active sites, and several nanocarrier systems have been explored for the topical administration of active components. The major disadvantage of the prepared nanosystems is their low viscosity, which reduces the time needed for enough absorption and negatively affects their stability and bioavailability. The role of semisolid systems is to overcome this limitation. In conclusion, this review presents an updated summary of recent advances in the use of semisolids as vehicles for various nanosystems through comprehensive scrutiny of the types of semisolids and their advantages and their role in enhancing the absorption of nanoparticles and nanovesicles.

Advancements in Ocular Modelling and Simulations: Key Considerations and Case Studies

This review paper discusses the key aspects of ocular biopharmaceutics, with emphasis on the crucial role played by ocular compartmental modelling and simulation in deciphering physiological conditions related to various eye diseases. It describes eye's intricate structure and function and the need for precise and targeted drug delivery systems to address prevalent eye conditions. The review categorizes and discusses various formulations employed in ocular drug delivery, delineating their respective advantages and limitations. Additionally, it probes the challenges inherent in diverse routes of drug administration for ocular therapies and provides insights into the complexities of achieving optimal drug concentrations at the target site within the eye. The central theme of this work is the ocular compartmental modelling and simulations. Hence, this works discusses on the nuanced understanding of physiological conditions within the eye, drug distribution, drug release kinetics, and key considerations for ocular compartmental modelling and simulations. By combining information from various sources, this review aims to serve as a comprehensive reference for researchers, clinicians, and pharmaceutical developers. It covers the multifaceted landscape of ocular biopharmaceutics and the transformative impact of modelling and simulation in optimizing ocular drug delivery strategies.

Opportunities of topical drug products in a changing dermatological landscape

Despite the prevalence and the impact on quality of life of dermatological indications, drug products to treat such conditions have rarely been blockbusters. The prevailing perception of a limited commercial potential of dermatological drug products has restricted innovation and encouraged a more conservative development approach. For example, the focus was on repurposing/reformulation of existing active pharmaceutical ingredients (APIs) specifically for the topical delivery route. However, the situation is quite different today catalyzed in part by the blockbuster success of Dupixent (dupilumab), the first monoclonal antibody treatment for atopic dermatitis which has been approved by the US Food and Drug Administration (US FDA) in 2017. Dupixent's success not only encouraged the development of other biologics but also inspired the (re-)development of new dermal drug products that can reap the many benefits of topical administration. We have also witnessed a shift toward outsourcing development efforts (and associated risks) towards small- to mid-size pharmaceutical companies which often require support of contract research and development/manufacturing organizations (CRO and CDMO). Such trends also emphasize the need of greater expertise in topical formulation design, as well as associated commercial and regulatory considerations. Today, we believe that topical drug products remain not only an essential but also commercially viable class of dermatological therapeutics. In this opinion article, we will address the challenges as well as opportunities of coherent development strategies in the current market environment, formulation innovations of topical drug products and technological advances to facilitate rational topical drug formulation development.

Stimuli-responsive drug delivery systems for inflammatory skin conditions

Inflammatory skin conditions highly influence the quality of life of the patients suffering from these disorders. Symptoms include red, itchy and painful skin lesions, which are visible to the rest of the world, causing stigmatization and a significantly lower mental health of the patients. Treatment options are often unsatisfactory, as they suffer from either low patient adherence or the risk of severe side effects. Considering this, there is a need for new treatments, and notably of new ways of delivering the drugs. Stimuli-responsive drug delivery systems are able to deliver their drug cargo in response to a given stimulus and are, thus, promising for the treatment of inflammatory skin conditions. For example, the use of external stimuli such as ultraviolet light, near infrared radiation, or alteration of magnetic field enables drug release to be precisely controlled in space and time. On the other hand, internal stimuli induced by the pathological condition, including pH alteration in the skin or upregulation of reactive oxygen species or enzymes, can be utilized to create drug delivery systems that specifically target the diseased skin to achieve a better efficacy and safety. In the latter context, however, it is of key importance to match the trigger mechanism of the drug delivery system to the actual pathological features of the specific skin condition. Hence, the focus of this article is placed not only on reviewing stimuli-responsive drug delivery systems developed to treat specific inflammatory skin conditions, but also on critically evaluating their efficacy in the context of specific skin diseases. STATEMENT OF SIGNIFICANCE: Skin diseases affect one-third of the world's population, significantly lowering the quality of life of the patients, who deal with symptoms such as painful and itchy skin lesions, as well as stigmatization due to the visibility of their symptoms. Current treatments for inflammatory skin conditions are often hampered by low patient adherence or serious drug side effects. Therefore, more emphasis should be placed on developing innovative formulations that provide better efficacy and safety for patients. Stimuli-responsive drug delivery systems hold considerable promise in this regard, as they can deliver their cargo precisely where and when it is needed, reducing adverse effects and potentially offering better treatment outcomes.

Topically Applied Therapies for the Treatment of Skin Disease: Past, Present, and Future

The purpose of this review is to summarize essential biological, pharmaceutical, and clinical aspects in the field of topically applied medicines that may help scientists when trying to develop new topical medicines. After a brief history of topical drug delivery, a review of the structure and function of the skin and routes of drug absorption and their limitations is provided. The most prevalent diseases and current topical treatment approaches are then detailed, the organization of which reflects the key disease categories of autoimmune and inflammatory diseases, microbial infections, skin cancers, and genetic skin diseases. The complexity of topical product development through to large-scale manufacturing along with recommended risk mitigation approaches are then highlighted. As such topical treatments are applied externally, patient preferences along with the challenges they invoke are then described, and finally the future of this field of drug delivery is discussed, with an emphasis on areas that are more likely to yield significant improvements over the topical medicines in current use or would expand the range of medicines and diseases treatable by this route of administration. SIGNIFICANCE STATEMENT: This review of the key aspects of the skin and its associated diseases and current treatments along with the intricacies of topical formulation development should be helpful in making judicious decisions about the development of new or improved topical medicines. These aspects include the choices of the active ingredients, formulations, the target patient population's preferences, limitations, and the future with regard to new skin diseases and topical medicine approaches.

The effect of skin diffusion kinetics of isopropyl ester permeation enhancers on drug permeation: Role of lateral spread and penetration characteristics

The purpose of present work was to study the effects of permeation enhancers' two kinetic behaviors of simultaneous lateral diffusion and vertical penetration in the skin on its enhancing effect. The skin diffusion kinetics of isopropyl ester permeation enhancers were characterized by the innovative concentric tape peeling study and Raman imaging, which were quantitatively assessed through innovative parameters, namely, lateral-to-vertical penetration amount (CL-V) and lateral-to-vertical penetration distance (DL-V). The enhancement effect of permeation enhancers on drug flurbiprofen (FLU) was assessed by in vitro skin permeation tests, which were confirmed by transdermal water loss and skin resistance study. The relationship between kinetic parameters of permeation enhancers and permeation parameters of FLU was carried out by correlation analysis. The molecular mechanisms of effect of skin diffusion kinetics of permeation enhancers on drug permeation were characterized by molecular docking, modulated-temperature differential scanning calorimetry (MTDSC), Raman spectra, solid-state NMR and molecular dynamic simulation. The results indicated skin diffusion kinetics of short-chain (C8-C12) isopropyl ester permeation enhancers were governed by vertical penetration, while long-chain (C14-C18) ones were characterized by lateral spread. Quadratic correlation between CL-V and enhancement ratio of permeation-retention ratio of FLU (ERQ/R) (R2 = 0.95), DL-V and enhancement ratio of permeation area (ERA) of FLU (R2 = 0.98) indicating that varied skin diffusion kinetics of permeation enhancers directly influenced the barrier function of stratum corneum (SC) and further enhancing drug permeation. In terms of molecular mechanism, long-chain isopropyl ester enhancers had good miscibility with SC, leading to their high CL-V and DL-V, and causing strong interaction strength with SC and resulting in weaker skin barrier function for drug permeation. In summary, in comparison to short-chain isopropyl ester enhancers that relied on penetration, long-chain ones that depended on lateral spread exhibited greater enhancement efficacy, which guided the application of enhancers in transdermal formulations.

Functional Nanostructured Lipid Carrier-Enriched Hydrogels Tailored to Repair Damaged Epidermal Barrier

In this study, a functional nanostructured lipid carriers (NLCs)-based hydrogel was developed to repair the damaged epidermal skin barrier. NLCs were prepared via a high-energy approach, using argan oil and beeswax as liquid and solid lipids, respectively, and were loaded with ceramides and cholesterol at a physiologically relevant ratio, acting as structural and functional compounds. Employing a series of surfactants and optimizing the preparation conditions, NLCs of 215.5 ± 0.9 nm in size and a negative zeta potential of -42.7 ± 0.9 were obtained, showing acceptable physical and microbial stability. Solid state characterization by differential scanning calorimetry and X-ray powder diffraction revealed the formation of imperfect crystal NLC-type. The optimized NLC dispersion was loaded into the gel based on sodium hyaluronate and xanthan gum. The gels obtained presented a shear thinning and thixotropic behavior, which is suitable for dermal application. Incorporating NLCs enhanced the rheological, viscoelastic, and textural properties of the gel formed while retaining the suitable spreadability required for comfortable application and patient compliance. The NLC-loaded gel presented a noticeable occlusion effect in vitro. It provided 2.8-fold higher skin hydration levels on the ex vivo porcine ear model than the NLC-free gel, showing a potential to repair the damaged epidermal barrier and nourish the skin actively.

Technological and Physical-Chemical Evaluation of Cotton Gauzes Impregnated with Semisolid Preparations for Wound Healing

Chronic wounds are marked by an extended healing period during which damaged tissues fail to undergo orderly and timely repair. Examples of chronic wounds encompass venous ulcers, pressure ulcers, and diabetic foot ulcers. The process of wound healing is complex and dynamic, relying on the interplay and response among various cells and mediators. In this study, four marketed wound dressing products based on cotton gauzes impregnated with different semisolid products (namely Betadine® 10%, Connettivina® Bio Plus Fitostimoline® Plus, and Non-Ad® gauzes) have been characterized for their physicochemical properties and ex vivo behaviors. More in detail, the pH and rheological features of semisolid formulations impregnating the gauzes were analyzed along with their ability to adhere to the gauzes. The most promising ones were selected and compared in ex vivo experiments on fresh pig skin. The pH measurements showed an acidic environment for all the tested solutions, albeit with variations in mean values, ranging from 2.66 to 4.50. The outcomes of rheological studies demonstrated that all the semisolid preparations impregnating the gauzes exhibited a pseudoplastic behavior, with significant differences in the pseudoplasticity index across the preparations, which is likely to influence their ability to adhere to the gauze. A rheological study in oscillatory mode revealed rheological behavior typical of a viscous solution only for the cream impregnating non-paraffin gauzes. The other products exhibited rheological behavior typical of a weak gel, which is expected to be advantageous as regards the capability of the semisolid preparation to create and maintain the space within the wound and to provide protection to the injured tissue. Results of ex vivo experiments demonstrated that Fitostimoline® Plus was more effective than Connettivina® Bio Plus in promoting both skin hydration and energy.

Acanthus mollis Formulations for Transdermal Delivery: From Hydrogels to Emulsions

Topical formulations of Acanthus mollis L. leaf and the optimization of the release of their active compounds and their topical bioavailability were investigated for the first time. In vitro, the release of active compounds from three formulations-an oil-in-water cream and two hydrogels (Carbopol 940 and Pluronic F-127)-was determined using Franz diffusion cells. Detection and quantification of the compounds was performed via high-performance liquid chromatography with a photodiode array (HPLC-PDA). DIBOA, a bioactive compound of this medicinal plant, exhibited release kinetics of the Weibull model for the Carbopol and Pluronic F-127 formulation, identifying it as a potential active agent to optimize the topical distribution of the formulations. The implications extend to applications in inflammation treatment and tyrosinase inhibition, suggesting that it can make a significant contribution to addressing skin conditions, including melanoma and various inflammatory diseases.