Active compounds release from semisolid dosage forms

In Vitro Study of Cyano-Phycocyanin Release from Hydrogels and Ex Vivo Study of Skin Penetration

BACKGROUND

This study explored the most suitable materials for incorporating cyano-phycocyanin (C-PC) into hydrogels, focusing on maintaining the C-PC's long-term structural integrity and stabilityNext, the release of C-PC from the hydrogels and its skin penetration were investigated.

METHODS

A series of 1% (w/w) C-PC hydrogels was prepared using various gelling agents and preservatives. Spectrophotometric measurements compared the amount of C-PC in the hydrogels to the initially added amount. After selecting the most suitable gelling agent and preservative, two C-PC hydrogels, with and without propylene glycol (PG) (Sigma-Aldrich, St. Louis, MO, USA), were produced for further testing. In vitro release studies utilized modified Franz-type diffusion cells, while ex vivo skin-permeation studies employed Bronaugh-type cells and human skin. Confocal laser scanning microscopy analyzed C-PC accumulation in the skin.

RESULTS

The findings demonstrated that sodium alginate (Sigma-Aldrich, St. Louis, MO, USA), hydroxyethyl cellulose (HEC) (Sigma-Aldrich, St. Louis, MO, USA), and SoligelTM (Givaudan, Vernier, Switzerland) are effective biopolymers for formulating hydrogels while maintaining C-PC stability. After 6 h, C-PC release from the hydrogel containing PG was approximately 10% or 728.07 (±19.35) μg/cm2, significantly higher than the nearly 7% or 531.44 (±26.81) μg/cm2 release from the hydrogel without PG (p < 0.05). The ex vivo qualitative skin-permeation study indicated that PG enhances C-PC penetration into the outermost skin layer.

CONCLUSION

PG's ability to enhance the release of C-PC from the hydrogel, coupled with its capacity to modify the skin barrier ex vivo, facilitates the penetration of C-PC into the stratum corneum.

Low drug load, high retention mometasone furoate cream with polyglyceryl - 3 oleate as a chemical enhancer: Formulation development, in vivo and in vitro evaluation and molecular mechanisms

The study aimed to create a low loading, high retention, easier to apply O/W mometasone furoate (MF) cream using a chemical enhancer (CE) approach to provide more options for patients with atopic dermatitis (AD) and to investigate molecular mechanisms of its increased release and retention. A Box-Behnken design determined the optimal formulation based on stability and in vitro skin retention. Evaluations included appearance, rheological properties, irritation, in vivo tissue distribution and pharmacodynamics. Molecular mechanisms of enhanced release were studied using high-speed centrifugation, molecular dynamics and rheology. The interaction between the CE, MF and skin was studied by tape stripping, CLSM, ATR-FTIR and SAXS. The formulation was optimized to contain 0.05% MF and used 10% polyglyceryl-3 oleate (POCC) as the CE. There was no significant difference from Elocon® cream in in vivo retention and pharmacodynamics but increased in vivo retention by 3.14-fold and in vitro release by 1.77-fold compared to the basic formulation. POCC reduced oil phase cohesive energy density, enhancing drug mobility and release. It disrupted skin lipid phases, aiding drug entry and formed hydrogen bonds, prolonging retention. This study highlights POCC as a CE in the cream, offering insights for semi-solid formulation development.

Tranexamic acid loaded in a physically crosslinked trilaminate dressing for local hemorrhage control: Preparation, characterization, and in-vivo assessment using two different animal models

This work aimed at formulating a trilaminate dressing loaded with tranexamic acid. It consisted of a layer of 3 % sodium hyaluronate to initiate hemostasis. It was followed by a mixed porous layer of 5 % polyvinyl alcohol and 2 % kappa-carrageenan. This layer acted as a drug reservoir that controlled its release. The third layer was 5 % ethyl cellulose backing layer for unidirectional release of tranexamic acid towards the wound. The 3 layers were physically crosslinked by hydrogen bonding as confirmed by Infrared spectroscopy. Swelling and release studies were performed, and results proposed that increasing number of layers decreased swelling properties and sustained release of tranexamic acid for 8 h. In vitro blood coagulation study was performed using human blood and showed that the dressing significantly decreased coagulation time by 70.5 % compared to the negative control. In vivo hemostatic activity was evaluated using tail amputation model in Wistar rats. Statistical analysis showed the dressing could stop bleeding in a punctured artery of the rat tail faster than the negative control by 59 %. Cranial bone defect model in New Zealand rabbits was performed to check for bone hemostasis and showed significant decrease in the hemostatic time by 80 % compared to the control.

A New Blend of Litsea cubeba, Pinus mugo, and Cymbopogon winterianus Essential Oil Active as an Anti-tyrosinase Ingredient in Topical Formulations

Tyrosinase is a target enzyme to be inhibited in order to reduce excessive melanin production and prevent typical age-related skin disorders. Essential oils are complex mixtures of volatile compounds, belonging mainly to monoterpenoids and sesquiterpenoids, which have been relatively little studied as tyrosinase inhibitors. Among the monoterpenoids, citral (a mixture of neral and geranial) is a fragrance compound in several essential oils that has shown interesting tyrosinase inhibitory activity. Although citral is listed as an allergen among the 26 fragrances in Annex III of the Cosmetics Directive 2003/15/EC, it can be safely used for the formulation of topical products in amounts that are not expected to cause skin sensitization, as shown by various commercially available products.The aim of this work was to evaluate two different formulations (oil/water emulsion, oily solution) containing a new combination of essential oils (Litsea cubeba, Pinus mugo, Cymbopogon winterianus) applied to the skin both in nonocclusive and partially occlusive modes. The blend is designed to reduce the concentration of citral to avoid potential skin reactions while taking advantage of the inhibitory activity of citral. Specifically, the amount of citral and other bioactive compounds (myrcene, citronellal) delivered through the skin was studied as a function of formulation and mode of application.The results show that an oil/water emulsion is preferable because it releases the bioactive compounds rapidly and minimizes their evaporative loss. In addition, semi-occluded conditions are required to prevent evaporation, resulting in higher availability of the bioactive compounds in viable skin.

Balsam Poplar Buds Extracts-Loaded Gels and Emulgels: Development, Biopharmaceutical Evaluation, and Biological Activity In Vitro

Balsam poplar buds have been used for wound healing and treating irritated skin in traditional medicine. Balsam poplar buds extracts exhibit anti-inflammatory, antioxidant, and antimicrobial effects. In recent years, scientific research has begun to validate some of these traditional uses, leading to an increased interest in balsam poplar buds as a potential source of natural remedies in modern medicine. The study aims to simulate semi-solid pharmaceutical forms with balsam poplar buds extract and evaluate their quality through biopharmaceutical research. The active compounds identified in Lithuanian poplar buds were p-coumaric acid, cinnamic acid, caffeic acid, galangin, pinocembrin, pinobanksin, and salicin. In gels, pH values ranged from 5.85 ± 0.05 to 5.95 ± 0.07. The determined pH values of emulgels ranged from 5.13 ± 0.05 to 5.66 ± 0.15. After 6 h, the release of active compounds from gels and emulgels ranged from 47.40 ± 2.41% to 71.17 ± 3.54. p-coumaric acid dominates in the balsam poplar buds extracts. The pH values of the prepared sem-solid pharmaceutical forms are suitable for use on the skin. The viscosity of the formulations depends on the amount of gelling agent. All formulations showed antioxidant activity. It is relevant to conduct a more extensive study on the influence of the chosen carrier on the release of active compounds from semi-solid formulations with an extract of balsam poplar buds.

Cutaneous Polymeric-Micelles-Based Hydrogel Containing Origanum vulgare L. Essential Oil: In Vitro Release and Permeation, Angiogenesis, and Safety Profile In Ovo

Origanum vulgare var. vulgare essential oil (OEO) is known as a natural product with multiple beneficial effects with application in dermatology. Oregano essential oil represents a potential natural therapeutic alternative for fibroepithelial polyps (FPs), commonly known as skin tags. Innovative formulations have been developed to improve the bioavailability and stability of essential oils. In this study, we aimed to evaluate the morphology of a polymeric-micelles-based hydrogel (OEO-PbH), the release and permeation profile of oregano essential oil, as well as to assess in vivo the potential effects on the degree of biocompatibility and the impact on angiogenesis in ovo, using a chick chorioallantoic membrane (CAM). Scanning electron microscopy (SEM) analysis indicated a regular aspect after the encapsulation process, while in vitro release studies showed a sustained release of the essential oil. None of the tested samples induced any irritation on the CAM and the limitation of the angiogenic process was noted. OEO-PbH, with a sustained release of OEO, potentially enhances the anti-angiogenic effect while being well tolerated and non-irritative by the vascularized CAM, especially on the blood vessels (BVs) in the presence of leptin treatment. This is the first evidence of in vivo antiangiogenic effects of a polymeric-micelle-loaded oregano essential oil, with further mechanistic insights for OEO-PbH formulation, involving leptin as a possible target. The findings suggest that the OEO-containing polymeric micelle hydrogel represents a potential future approach in the pathology of cutaneous FP and other angiogenesis-related conditions.

Nanostructured Lipid Carriers (NLC)-Based Gel Formulations as Etodolac Delivery: From Gel Preparation to Permeation Study

Topical administration of drug is an attractive alternative to the oral administration as it provides a reduction in adverse reactions and an enhancement of therapeutic effects. The use of lipid carriers in hydrogel structures makes it possible to introduce lipophilic substances in a dissolved form. In this study, an NSAID from the BCS class II, etodolac (ETD), was used. The nanostructured lipid carriers (NLC) obtained with ETD were incorporated into semi-solid forms (gels). Hydrogels with the suspended drug and oleogel were also prepared for comparison purposes. The obtained gels were tested in terms of pH, viscosity, rheological, mechanical, and bioadhesive properties. The release and permeation through membranes were also studied. All tested formulations were characterized by a pH below 7, which ensured the physiological state of the skin. The viscosities of all gels decreased with increasing shear rate, indicating non-Newtonian behavior. The fastest ETD release was observed for NLC with a Carbopol base (formulation F1); a similar result was noticed in the permeation test. The developed gel formulations containing ETD-NLC dispersion and Carbopol or Poloxamer as gelling agents were stable and possessed beneficial pharmaceutical properties.

Hemostatic Alginate/Nano-Hydroxyapatite Composite Aerogel Loaded with Tranexamic Acid for the Potential Protection against Alveolar Osteitis

Wound control in patients on anticoagulants is challenging and often leads to poor hemostasis. They have a higher tendency to develop alveolar osteitis after tooth extraction. The application of a hemostatic dressing that has a high absorbing capacity and is loaded with an antifibrinolytic drug could help in controlling the bleeding. Alginate/nano-hydroxyapatite (SA/Nano-HA) composite aerogels loaded with tranexamic acid (TXA) were prepared. Nano-HA served as a reinforcing material for the alginate matrix and a source of calcium ions that helps in blood clotting. It influenced the porosity and the water uptake capacity. TXA release from SA/Nano-HA aerogels showed a biphasic profile for up to 4 h. Blood coagulation studies were performed on human whole blood. The TXA-loaded aerogel significantly reduced the clotting time by 69% compared to the control (p < 0.0001). Recalcification time was significantly reduced by 80% (p < 0.0001). Scanning electron microscopy analysis revealed the porous nature of the aerogels and the ability of the optimum aerogel to activate and adhere platelets to its porous surface. The cell migration assay showed that there was a delay in wound healing caused by the TXA aerogel compared to the control sample after treating human fibroblasts. Results suggest that the developed aerogel is a promising dressing that will help in hemostasis after tooth extraction.

An Update to Dialysis-Based Drug Release Testing-Data Analysis and Validation Using the Pharma Test Dispersion Releaser

Currently, a wide variety of complex non-oral dosage forms are entering the global healthcare market. Although many assays have been described in recent research, harmonized procedures and standards for testing their in vitro performance remain widely unexplored. Among others, dialysis-based techniques such as the Pharma Test Dispersion Releaser are developed for testing the release of drugs from nanoparticles, liposomes, or extracellular vesicle preparations. Here, we provide advanced strategies and practical advice for the development and validation of dialysis-based techniques, including documentation, analysis, and interpretation of the raw data. For this purpose, key parameters of the release assay, including the hydrodynamics in the device at different stirring rates, the selectivity for particles and molecules, as well as the effect of excipients on drug permeation were investigated. At the highest stirring rate, a more than twofold increase in the membrane permeation rate (from 0.99 × 10⁻³ to 2.17 × 10⁻³ cm²/h) was observed. Additionally, we designed a novel computer model to identify important quality parameters of the dialysis experiment and to calculate error-corrected release profiles. Two hydrophilic creams of diclofenac, Voltaren^® Emulgel, and Olfen^® gel, were tested and provide first-hand evidence of the robustness of the assay in the presence of semisolid dosage forms.

Comparative in vitro release testing (IVRT) of acyclovir products

The aim was to evaluate whether an in vitro release test (IVRT) could differentiate the release rates from five pharmaceutically equivalent acyclovir cream products and one ointment compared to that from a reference product, Zovirax cream (USA), to identify a test product with an inequivalent drug release rate that could serve as negative control for bioequivalence (BE) in a separate in vivo study. The reference product showed equivalent drug release rates compared to itself. The six test products failed to show equivalent drug release rates compared to the reference product. Aciclovir 1A pharma cream was selected to serve as a negative control for subsequent BE studies, since it exhibited the greatest difference in release rate among all creams, compared to the reference product. The results of this study indicate that IVRT results can be highly sensitive and may discriminate clinically relevant differences between products. Results from an appropriately validated IVRT method can support a demonstration of BE by showing that the drug release rates from test and reference products are statistically equivalent, mitigating the risk that differences may exist between the products which may influence in vivo performance of the drug product.

The Influence of Tea Tree Oil on Antifungal Activity and Pharmaceutical Characteristics of Pluronic® F-127 Gel Formulations with Ketoconazole

Fungal skin infections are currently a major clinical problem due to their increased occurrence and drug resistance. The treatment of fungal skin infections is based on monotherapy or polytherapy using the synergy of the therapeutic substances. Tea tree oil (TTO) may be a valuable addition to the traditional antifungal drugs due to its antifungal and anti-inflammatory activity. Ketoconazole (KTZ) is an imidazole antifungal agent commonly used as a treatment for dermatological fungal infections. The use of hydrogels and organogel-based formulations has been increasing for the past few years, due to the easy method of preparation and long-term stability of the product. Therefore, the purpose of this study was to design and characterize different types of Pluronic^® F-127 gel formulations containing KTZ and TTO as local delivery systems that can be applied in cases of skin fungal infections. The influence of TTO addition on the textural, rheological, and bioadhesive properties of the designed formulations was examined. Moreover, the in vitro release of KTZ, its permeation through artificial skin, and antifungal activity by the agar diffusion method were performed. It was found that obtained gel formulations were non-Newtonian systems, showing a shear-thinning behaviour and thixotropic properties with adequate textural features such as hardness, compressibility, and adhesiveness. Furthermore, the designed preparations with TTO were characterized by beneficial bioadhesive properties. The presence of TTO improved the penetration and retention of KTZ through the artificial skin membrane and this effect was particularly visible in hydrogel formulation. The developed gels containing TTO can be considered as favourable formulations in terms of drug release and antifungal activity.

The Potential of a Site-Specific Delivery of Thiamine Hydrochloride as a Novel Insect Repellent Exerting Long-Term Protection on Human Skin: In-vitro, Ex-vivo Study and Clinical Assessment

Thiamine hydrochloride (TH) was thought to exert a good insect repellent activity. The purpose of this work was to develop a formulation that releases TH in sustained regimen on human skin. Long lasting protection against mosquito bites was achieved. Pullulan acetate (PA) was used to prepare TH nanospheres. Optimal system was incorporated in Pluronic® hydrogel. Formulae were tested for in-vitro release and ex-vivo permeation. Complete protection time (CPT) was done adopting Kaplan-Meier survival function for the synthetic repellent (DEET), TH solution and nanospheres in hydrogel. Release profile of TH solution, nanospheres and nanosphere-loaded hydrogel (DG) demonstrated an added effect of DG, where t _1/2 was 11.2 ± 1.4 h. SEM for DG showed homogenous dispersion of nanospheres inside the matrix of the gel. Ex-vivo permeation showed only 0.761 ± 0.04% of TH in hydrogel permeated the skin after 12 h, while 44.98 ± 3.2% permeated when TH solution was applied. Clinical study revealed a significant difference in CPT between TH solution with either DEET or (DG) (p<0.05), and no significant difference between DEET and DG with CPT 400 ± 31 and 360 ± 18 min, respectively (P > 0.05). The high efficacy of TH-loaded hydrogel rendered it a successful alternative for DEET, offering long protection against mosquito bites.

Impact of Membranes on In Vitro Release Assessment: a Case Study Using Dexamethasone

In vitro release studies are commonly used to assess the product performance of topical dosage forms. In such studies, the mass transport of drugs through synthetic membranes into a receiving chamber filled with a release medium is measured. The release medium is also passed through filtration membranes prior to chromatographic analysis. There are no official guidelines directing membrane selection for in vitro release studies or for filtration. Considering the diversity in membrane materials and their physical properties, the aim of this study was to investigate membrane-drug binding and the effect of various membranes on the release performance of a model drug dexamethasone (DEX) using USP dissolution apparatus IV. Seven membranes of different pore sizes (0.45 and 1.2 μm) and materials (cellulose acetate, polyethersulfone, and nylon) were assessed. Two different methods, syringe filter and 24-h incubation, were used for the determination of membrane-drug binding effects at low drug concentrations and saturated concentration conditions. Cellulose acetate and nylon membranes showed significant drug binding after 24-h incubations at both drug concentrations. DEX diffusion through membranes was significantly slowed down in all the tested membranes when compared with DEX solution without membranes. The extent of the retardation varied due to the differences in membrane structures. In conclusion, materials and sources of membranes affected drug dissolution profiles and the results showed membrane-drug binding effects. Proper selection of membranes with low drug binding ability and low diffusion resistance is essential to ensure appropriate and reproducible in vitro release assessments and filtration studies. Graphical Abstract.

In Vitro Release Testing of Acyclovir Topical Formulations Using Immersion Cells

The objective of the study was to reinforce the applicability of the immersion cells for the in vitro release testing (IVRT) of topical formulations by using marketed acyclovir 5% cream formulation (Cream 1) as a model. The method employing the immersion cells was optimized by studying the effect of variables, such as membrane type, media temperature and volume, agitation speed, and cell size, on acyclovir release from the formulation. The in-house formulation similar to the qualitative and quantitative composition of Cream 1 and the other trial formulations with variable compositions were prepared and studied by using the immersion cells. Various other brands of acyclovir topical formulations available in the Indian market were also subjected to IVRT by using the optimized method. An increase in the media temperature from 32°C to 37°C and the stirring speed from 50 to 100 to 150 rpm led to an increase in the drug release. As the immersion cell size increased (0.5, 2 and 4 cm² surface area), the release rate also increased. Nitrocellulose membrane showed the highest drug release and Fluoropore^™ the least. The optimized IVRT method could establish the differences in the drug release rates among the formulations with the altered compositions. The method could also prove its discriminatory potential for various marketed formulations. The immersion cell method could serve as a simpler, facile, and reliable aid during product development and also as a quality control tool in assessing stability, aging, and batch-to-batch uniformity of semisolid formulations.

Influence of in vitro release methods on assessment of tobramycin ophthalmic ointments

The current investigation was carried out to identify appropriate parameters for measuring the in vitro release of tobramycin (TOB) ophthalmic ointments and to evaluate the feasibility of in vitro release testing methods to assess the product performance. Drug release was assessed using USP dissolution apparatus IV and a modified USP dissolution apparatus I with simulated tear solution (STS) as the dissolution medium. The study variables included temperature, membrane material, source and pore size. The results demonstrated a significant influence of the membrane source and pore size on the release of TOB from the ointments. A dissolution medium temperature of 40 °C was found to be appropriate for the release studies. Both of the apparatuses were able to discriminate between the release profiles of ointments with different physicochemical/rheological properties. Maximum release rate of TOB was observed in the first hour which followed a logarithmic time dependent release. The correlation between the release rates/amounts and yield stress of the ointments was observed in both the dissolution apparatuses. These results support a rational approach to guide the in vitro release testing of TOB ophthalmic ointments.

Inhibitory Effect of Roselle Aqueous Extracts-HPMC 6000 Gel on the Growth of Staphylococcus Aureus ATCC 25923

Objectives

Roselle (Hibiscus sabdariffa L.) is a medicinal plant commonly used as a beverage and herbal medicine. Complex compounds in the aqueous extracts have provided good antibacterial activity by which the growth of gram-negative and -positive bacteria is inhibited. The aims of this research were to formulate hydroxypropyl methylcellulose (HPMC) 6000 gel containing the extract and investigate the inhibitory activity of the extract and its gel formula against Staphylococcus aureus ATCC 25923.

Materials and Methods

Thin layer chromatography (TLC) on silica gel GF254 was used for analyzing flavonoids and polyphenols using butanol: acetic acid: water (4:1:5) and chloroforms: ethyl acetate: formic acid (0.5:9:0.5) as eluent, respectively. A serial dilution of aqueous extract powder in citrate buffer was made to obtain 0.50, 0.25, 0.10, 0.05, and 0.02 mg/mL solution. The roselle aqueous extract (3%) was formulated as a component of gel containing HPMC 6000 in various concentrations (2%, 3%, and 4%). A diffusion agar method on two layers of nutrient agar media was applied using Staphylococcus aureus ATCC 25923 and gentamicin 25 ppm as bacterial test and standard, respectively. After incubation for 24 h at 37°C, the inhibitory effect was denoted by a clear zone around the hole and the inhibitory activity was measured as minimum inhibitory concentration (MIC).

Results

The aqueous extract of Hibiscus sabdariffa L. contained flavonoid and polyphenol compounds based on the TLC chromatogram profile. It was found that the gel formula containing 3% HPMC 6000 and 3% aqueous extract gave a good physical characteristic and the lowest MIC (6.0 mg/mL), equivalent to 7.58 ppm of gentamicin standard at 12.0 mg/mL concentration.

Conclusion

The HPMC 6000 at 3% (w/w) concentration in roselle aqueous extract gel preparation gave good physical characteristics. The gel preparation exhibited inhibitory activity against Staphylococcus aureus ATCC 25923 shown by MIC 6.0 mg/mL. Formula 2 is recommended and should be further investigated for implementation in topical preparations.

A Validated IVRT Method to Assess Topical Creams Containing Metronidazole Using a Novel Approach

An IVRT method was developed and validated to confirm its reproducibility, precision, sensitivity, selectivity, accuracy, robustness, and reliability. A novel approach was used to demonstrate the appropriateness of the IVRT method to accurately assess "sameness" between topical products and to confirm that the methodology applied also possesses the requisite discriminatory power to detect differences should such differences exist between products. In the first instance, the reference product (Metrocreme®) containing 0.75% metronidazole (MTZ) was tested against itself as a positive control, to accurately demonstrate "sameness", where the results met the relevant acceptance criteria falling within the limits of 75-133.33% in accordance with the FDA's SUPAC-SS guidance. In addition, two specially prepared creams containing 25% less and 26% more MTZ, i.e., 0.563% and 0.945%, served as negative controls and were compared against the reference product. Neither of these creams fell within the "sameness" acceptance criteria, thereby confirming the discriminatory ability of the IVRT method to detect differences between MTZ products. Furthermore, another cream containing 0.75% MTZ tested against the reference product was shown to be pharmaceutically equivalent to the reference product. These results confirm the appropriateness of the IVRT method as a valuable tool for use in the development of topical MTZ products intended for local action and indicate the potential for general use with other topical products.

Perspectives on Physicochemical and In Vitro Profiling of Ophthalmic Ointments

Ophthalmic ointments are unique in that they combine features of topical drug delivery, the ophthalmic route and ointment (semisolid) formulations. Accordingly, these complex formulations are challenging to develop and evaluate and therefore it is critically important to understand their physicochemical properties as well as their in vitro drug release characteristics. Previous reports on the characterization of ophthalmic ointments are very limited. Although there are FDA guidance documents and USP monographs covering some aspects of semisolid formulations, there are no FDA guidance documents nor any USP monographs for ophthalmic ointments. This review summarizes the physicochemical and in vitro profiling methods that have been previously reported for ophthalmic ointments. Specifically, insight is provided into physicochemical characterization (rheological parameters, drug content and content uniformity, and particle size of the API in the finished ointments) as well as important considerations (membranes, release media, method comparison, release kinetics and discriminatory ability) in in vitro release testing (IVRT) method development for ophthalmic ointments. Graphical Abstract Summary of the physicochemcial profiling and in vitro drug release testing (IVRT) for ophthalmic ointments.

Release studies of undecylenoyl phenylalanine from topical formulations

The aim of this study was to characterize the stability of new vehicles for the undecylenoyl phenylalanine that is used as skin-lightening agent in the melasma treatment. The purpose of this research was also to analyse the release kinetics of phenylalanine derivative from topical preparations through different synthetic membranes. Topical formulations such as two different macroemulsions, hydrogels (based on carbomer and hydroxyethylcellulose) and microemulsions were characterized in terms of stability by laser diffraction method. Additionally, multiple light scattering assessed the stability of macroemulsions. The release rates of active substance through different membranes (such as Cuprophan, nitrocellulose, cellulose acetate and Strat-M) were determined using enhancer cell. In order to explain the mechanism of release process the results were fitted with different kinetic models. New stable vehicles for Ude-Phe were successfully obtained. The results proved that the membrane structure had the influence on the release rate of undecylenoyl phenylalanine. The slowest release rate of Ude-Phe was observed when Strat-M membrane was applied. The highest amount of active substance was released from the hydrogel based on carbomer. The release of undecylenoyl phenylalanine from both macroemulsions and hydrogel based on hydroxyethylcellulose followed the Higuchi model. Whereas the release results of Ude-Phe from both microemulsion-based hydrogels and carbomer hydrogel can be described by using Korsmeyer-Peppas model. Hydrogels and microemulsion-based hydrogels could be recommended as proper vehicles for the derivative of phenylalanine.

Influence of Testing Parameters on In Vitro Tramadol Release from Poloxamer Thermogels using the Immersion Cell Method

The immersion cell is an in vitro performance test of drug release from semisolids. Several studies made use of immersion cells to investigate drug release from thermosensitive Poloxamer-based gels; however, specifications on the parameter setting are not yet available. Therefore, the aim of this study was to evaluate the influence of testing parameters on tramadol (a model drug) release, release rate, and dissolution efficiency (DE) from Poloxamer gels, using immersion cells. The thermosensitive gelling formulation showed batch-to-batch uniformity of gelling behavior, drug content, and drug release. The use of a membrane in the immersion cell resulted in slower drug release as compared to the absence of a membrane. Moreover, the faster the paddle rotation, the faster the drug release was. Membrane thickness showed a strong and significant linear relationship with corresponding DE values (Pearson's correlation coefficient, r = -0.9470; p = 0.004). Factors that did not influence drug release include paddle position, i.e., distance between paddle and membrane, as well as membrane mean pore size. This study sets forth the importance of carefully controlling the following parameters including presence/absence of membrane, paddle rotation speed, and membrane thickness during the setup of release experiments from gels using immersion cells.

Physico-chemical characterization of formulations containing endomorphin-2 derivatives

In this study semisolid formulations containing AcYPFF (N-acetyl-Tyr-Pro-Phe-Phe-NH₂) tetrapeptide were obtained and characterized in terms of rheology, stability by multiple light scattering and particle size distribution by laser diffraction. Additionally, the release studies of tetrapeptide from formulations obtained were performed. The influence of different factors such as semisolid and membrane type on tetrapeptide release rate was examined. The release experiments of tetrapeptide modified with palmitoyl group (PalmYPFF) were also carried out. The results proved that formulation type and its rheological properties strongly determined the permeation process of the tetrapeptide. The fastest release of tetrapeptide was observed from hydrogel that had the lowest viscosity. The kinetic data of tetrapeptide released from oil-in-water (o/w) and water-in-oil (w/o) emulsions prepared at elevated temperature showed good fit to the Higuchi equation, whereas when AcYPFF was released from oil-in-water (o/w) emulsion prepared with the addition of auto-emulsifier high linearity with Korsmeyer–Peppas model was observed. While when tetrapeptide was released from Hydrogel the most suitable model was the first-order kinetics. It was suggested that mechanism that led to the release of tetrapeptide from all formulations was non-Fickian diffusion transport. The presence of palmitoyl group changed the solubility of tetrapeptide both in formulation and receptor fluid and thus the release rate of active compound was modified.

Development of an Ointment Formulation Using Hot-Melt Extrusion Technology

Ointments are generally prepared either by fusion or by levigation methods. The current study proposes the use of hot-melt extrusion (HME) processing for the preparation of a polyethylene glycol base ointment. Lidocaine was used as a model drug. A modified screw design was used in this process, and parameters such as feeding rate, barrel temperature, and screw speed were optimized to obtain a uniform product. The product characteristics were compared with an ointment of similar composition prepared by conventional fusion method. The rheological properties, drug release profile, and texture characteristics of the hot-melt extruded product were similar to the conventionally prepared product. This study demonstrates a novel application of the hot-melt extrusion process in the manufacturing of topical semi-solids.

Development and validation of an in vitro release method for topical particulate delivery systems

The aim of this study was to develop an in vitro release method for topical particulate delivery systems using the immersion cell in combination with paddle dissolution apparatus. Chitosan- and methacrylate-based microparticles with mupirocin were prepared and used as model topical delivery systems for method development. Diffusion of the drug occurred across a mixed cellulose ester membrane, which demonstrated low drug adsorption and low diffusional resistance. After an initial lag phase the amount of drug released became proportional to the square root of time. The method was discriminative toward differences in formulation, as well as toward differences in drug concentration inside the sample compartment. The method was further used to confirm sameness between batches of the same composition prepared by the same process. Variations in paddle rotation speed (25 rpm, 50 rpm, 100 rpm), paddle height (1cm, 2.5 cm) and volume of release medium (100ml, 200 ml) did not significantly alter the release rates. The method of analysis was validated according to ICH guidelines. Currently there are no compendial or standard methods and apparatuses for in vitro release testing of topical microparticles. The developed method can be a useful guide in formulation development of such delivery systems.

Characterization of supramolecular gels based on β-cyclodextrin and polyethyleneglycol and their potential use for topical drug delivery

Novel gels were prepared by blending β-cyclodextrin and polyethyleneglycol (PEG) in the presence of K2CO3. The objective of this study was thus to characterize the gels using rheology, modulated temperature differential scanning calorimetry (MTDSC), turbidity measurements, and hot stage microscopy, and then investigate the potential use of the gel for topical drug delivery. Two types of supramolecular gels, GelL and GelH were prepared at a low temperature (below 50 °C) and at a high temperature (above 70 °C), respectively. Both gels were thermo-reversible. Upon heating, GelL could turn to GelH. Nevertheless, upon cooling, GelH that was more stable than GelL precipitated and GelL could not be reformed. GelL may form through simple complexation of polyethyleneglycol (PEG) with β-cyclodextrin in the presence of K2CO3. However, GelH may form a specific complex or a pseudopolyrotaxane gel. For pharmaceutical application, GelL was investigated instead of GelH because the forming temperature of this gel was close to the human body temperature. The interactions among diclofenac sodium (DS), a model drug, and the components of the gel were examined using FTIR. These interactions may include ionic attraction and hydrogen bonds between the carboxylate groups of DS and the hydroxyl groups of PEG or β-cyclodextrin and probably also the inclusion of the aromatic ring of DS into the cavity of β-cyclodextrin. Furthermore, the release and permeation of diclofenac from GelL were significantly greater than those from a commercial gel. Therefore, GelL may be useful for the topical delivery of drugs.

Demonstrating comparative in vitro bioequivalence for animal drug products through chemistry and manufacturing controls and physicochemical characterization: a proposal

The assessment of in vivo bioequivalence (BE) of nonsystemically absorbed drug products has been a longstanding challenge facing drug manufacturers and regulators of human or animal health products. Typically, in situations where blood level BE studies are not feasible, clinical endpoint BE trials have provided the only option for generating interproduct comparisons. Given the imprecision and logistic challenges associated with these studies, there has been an effort to identify alternative pathways that can reliably ensure the equivalence of product performance and quality. This commentary provides a proposal for an in vitro approach for evaluating the in vivo BE of veterinary drug products that are either nonsystemically absorbed or that act both locally and systemically but where the local site of action is proximal to the absorption window. The assumption underlying this approach is that equivalence in product physicochemical attributes and in vitro product performance translates to equivalence in product in vivo behavior. For sponsors with a right of reference to underlying safety and effectiveness data, this approach could be used to support pre and post-approval changes. When comparing a generic test product to the pioneer (reference listed new animal drug, RLNAD) product, a demonstration of sameness across a battery of in vitro test procedures could be used to confirm that the test and RLNAD products are bioequivalent.

Could albumin affect the self-assembling properties of a block co-polymer system and drug release? An in-vitro study

PURPOSE

This work investigated the influence of a model protein, bovine serum albumin (BSA), on the properties of a thermogelling formulation intended for administration inside body compartments where there is high albumin content, as in the case of inflamed joints; it also explored the relation between the variation of these properties and release performance of methotrexate (MTX), a drug used to treat forms of arthritis and rheumatic conditions.

METHODS

The influence of BSA on the micellisation and gelation behaviour of Poloxamer 407, chosen as a model copolymer, was studied by differential scanning calorimetry (microDSC), dynamic light scattering (DLS), fluorescence spectroscopy and rheology studies. A release study of MTX loaded inside the hydrogel in presence and in absence of BSA was performed.

RESULTS

DLS and microDSC data revealed that the micellisation process was not affected by the protein, as demonstrated by unaltered micellar size and thermodynamic parameters. While the presence of BSA in the copolymer system reduced gel consistency, the hydrogel release performance was only slightly affected.

CONCLUSION

Our results suggested that the kinetics of MTX release mainly depended on the presence of the thermogelling copolymer, although other mechanisms related to BSA could be involved. Finally, the study assessed the feasibility of using a thermogelling hydrogel for in situ drug administration in areas with the presence of high protein concentrations.

In vitro drug release and ex vivo percutaneous absorption of resveratrol cream using HPLC with zirconized silica stationary phase

Since the designs of optimal formulations for resveratrol permeation via the skin are lacking, the aim of this study was to establish the profile of resveratrol permeability into and across human skin. For that, a laboratory-made chromatographic column was used (Zr-PMODS), with its performance being compared to a traditional C18 column. In vitro drug release was conducted with polysulfone membranes, and the flux (JS) was 30.49 μg cm(-2) h(-1)), with a lag time (LT) of 0.04 h, following a pseudo-first-order kinetics. For ex vivo percutaneous absorption using excised female human skin, the kinetic profile was the same, but JS was 0.87 μg cm(-2) h(-1) and LT was 0.97 h. From the initials 49.30 μg applied to the skin, 9.50 μg were quantified in the receptor medium, 20.48 μg was retained at the stratum corneum (do not account as permeated) and 21.41 μg was retained at the viable epidermis+dermis (account as permeated), totalizing 30.90 μg of resveratrol permeated after 24 h of application (62.6%). From these results, one can conclude that a person using the 1-g emulsion dose released by the pump containing 20mg of resveratrol will have, theoretically, 12.53 mg of it liberated into his bloodstream, gradually and continuously for 24 h.

Development of ciclopirox olamine topical formulations: evaluation of drug release, penetration and cutaneous retention

With the aim of reducing system absorption and consequently, the side effects, and simultaneously select a penetration enhancing, three topical formulations with 0.5% ciclopirox olamine (CO) and 15% of propylene glycol (PG), ethoxydiglycol or oleic acid were developed and evaluated regarding the skin penetration and cutaneous retention of the drug using Franz diffusion cells. Release experiments were performed through synthetic membrane while dermatomed pig ear skin was used to evaluate CO skin penetration and skin retention. Retention studies were carried out applying tape stripping method and dosing CO in stratum corneum and in epidermis and dermis. A HPLC method was validated for quantifying CO. All formulations tested with synthetic membrane presented no retention of the drug. Permeation data suggested that there was no systemic absorption of ciclopirox olamine from the studied formulations, even when the skin penetration enhancers were applied. Higher concentrations of the drug were found in the stratum corneum (SC) and also in epidermis and dermis, for all of the developed formulations. The addition of enhancers improved the penetration and cutaneous retention of CO, and propylene glycol promoted higher concentrations in epidermis and dermis, probably because its cumulative effect on the skin and by an efficient solvent power.

Release of Propolis Phenolic Acids from Semisolid Formulations and Their Penetration into the Human SkinIn Vitro

Antioxidant and free radical scavenging effects are attributed to phenolic compounds present in propolis, and when delivered to the skin surface and following penetration into epidermis and dermis, they can contribute to skin protection from damaging action of free radicals that are formed under UV and premature skin aging. This study was designed to determine the penetration of phenolic acids and vanillin into the human skinin vitrofrom experimentally designed vehicles. Results of the study demonstrated the ability of propolis phenolic acids (vanillic, coumaric, caffeic, and ferulic acids) and vanillin to penetrate into skin epidermis and dermis. The rate of penetration and distribution is affected both by physicochemical characteristics of active substances and physical structure and chemical composition of semisolid vehicle. Vanillin and vanillic acid demonstrated relatively high penetration through epidermis into dermis where these compounds were concentrated, coumaric and ferulic acids were uniformly distributed between epidermis and dermis, and caffeic acid slowly penetrated into epidermis and was not determined in dermis. Further studies are deemed relevant for the development of semisolid topically applied systems designed for efficient delivery of propolis antioxidants into the skin.