MICROEMULSION FORMULATIONS DEVELOPED FOR WOUND-BURN TREATMENT

Technical Field of the Invention

The invention relates to a microemulsion formulation having high penetration properties into the skin containing antibacterial effective fucidic acid and/or its salts and local anesthetic effective benzocaine and/or salt developed for use in the treatment of wounds and bums, and to a method of preparation thereof.

State of the Art of the Invention (Prior Art)

There are many active substances used in the treatment of the disease and there are commercial formulations developed with these active substances. However, the formulations known in the art are generally oil-based cream, ointment formulations or water-based gel formulations. These carrier systems have limited penetration into the lower layers of the skin. Microemulsion carrier systems where the active substances are loaded have gained importance in recent years for this reason.

Microemulsions are structures consisting of oil, surfactant, cosurfactant and water phase. Microemulsions are modem pharmaceutical drug delivery systems that have the ability to pass through the stratum cornea and reach the substrates of the skin. The preparation of microemulsions is fairly easy and there is no need for special apparatus and equipment for both small-scale and large-scale production. They can be basically prepared using a stirrer and heater.

Substances with different pharmacological effects such as antibacterial agents, local anesthetics, analgesics, anti-inflammatory agents can be used in wound-burn treatment. The active substances with these effects are commercially available on the market alone or sometimes as a combined preparation. For example, fucidic acid is an antibacterial agent used in wound-burn treatment. This active substance has commercial cream formulations. A microemulsion system that can increase the antibacterial effect of fucidic acid in the treatment of burns was designed in the study conducted by Neslihan Ustiindag Okur et al. The types and amounts of use of cosurfactant and surfactant substances, which are the excipients used, were also optimized accordingly since only fucidic acid is used as the active substance.

The invention relates to the method of preparing the microemulsion-based hydrogel formulation containing the benzocaine active substance in patent document TR 2015/10892. The hydrogel formulation is expected to show only local anesthetic effect since the formulation contains only benzocaine as the active substance.

A microemulsion system was designed in which analgesic effective indomethacin and local anesthetic effective benzocaine can be presented together and the passage of active substances through the skin can be increased in the study conducted by Mohamed A. Osman et al.

Briefly, there is no microemulsion system design and drug formulation study in which fucidic acid and benzocaine are combined in the known state of the art.

Brief Description and Objects of the Invention

The object of the invention is to design a microemulsion formulation that can synergistically show the local anesthetic effect of benzocaine with the antibacterial effect of fucidic acid in the treatment of wounds and burns and to increase the bioavailability of the active substances by increasing their passage through the skin with the developed microemulsion-based system.

A microemulsion-based combined formulation of antibacterial effective fucidic acid and local anesthetic effective benzocaine active substances was prepared with the invention. Both antibacterial and local anesthetic effects can be achieved with a single application, and higher efficacy can be obtained compared to the cream formulation by penetrating a higher amount of skin thanks to the carrier system microemulsion in this way.

The in vitro release data of the formulation, which was developed due to the absence of a commercial product containing these two substances in the market, were compared with the commercial preparation Fucidin cream (Fucidic acid) and the prepared Benzocaine solution. It was observed that the formulation developed in the obtained data gave better results against both products.

It was aimed to provide both antibacterial and anesthetic effects by developing a microemulsion-based formulation in which these two active substances are together. Thus, high patient compliance can be achieved by both healing and less pain and ache by using a single formulation. This is an important advantage in terms of pharmacological effect compared to the formulations in which fucidic acid is included alone. In addition, these two active substances are presented together with a microemulsion-based carrier. Microemulsions are colloidal carriers that increase the passage of the active substance through the skin. Since the Y/S-based microemulsion of these two oil-soluble active substances has higher permeability properties, it increases the bioavailability of both active substances. However, since microemulsions do not reach the vessels in the dermis, they do not cause an increase in the systemic side effects of the active substances.

The invention formulation is used in the preparation of the drug to be used for the treatment of wounds and burns.

Definitions of Figures Describing the Invention

Figure 1: The in vitro release comparison graph of the fucidic acid and benzocaine release in the microemulsion formulation developed by the invention with the benzocaine solution and the fucidin cream containing the commercially available fucidic acid is shown.

Detailed Description of the Invention

The invention relates to a microemulsion formulation having high permeability properties containing antibacterial effective fucidic acid and local anesthetic effective benzocaine developed for the treatment of wounds and burns, and to a method of preparation thereof.

Inventive microemulsion formulation effective in wound and bum treatment comprises the following; Antibacterial fucidic acid and/or its salts in the range of 0.1-10% by weight and local anesthetic benzocaine and/or its salt in the range of 0.1-20% by weight as active substance,

• Ethyl oleate in the range of 1-30% by weight as the oil phase,

• Water in the range of 5-30% by weight as water phase,

• Surfactant in the range of 1-50% by weight,

• Cosurfactant in the range of 5-50% by weight.

The surfactant is selected from sorbitan oleate/monooleate and its derivatives, PEG (Polyethylene glycol) sorbitan oleate/monooleate and its derivatives, PEG lauryl ether and its derivatives, PEG-castor oil and its derivatives in the formulation of the invention. Preferably Cremophor EL (Polyoxyl 35 Hydrogenated Castor Oil) was used as the surfactant in the invention.

The cosurfactant in the formulation of the invention may be propylene glycol, glycerin, and/or ethanol. A mixture of propylene glycol and ethanol, preferably in a ratio of 1 : 1, was used as the cosurfactant in the invention.

Benzocaine and fucidic acid are coexisting in a microemulsion-based carrier in the formulation of the invention.

The drug to be used in wound and burn treatment comprises the invention formulation.

The invention formulation may also include local anesthetic and/or local antibacterials. It contains lidocaine, procaine, chloroprocaine, mepivacaine, prilocaine, tetracaine, etidocaine, bupivacaine or kincocaine as local anesthetics. It contains mupirocin amikacin, bacitracin, gentamycin, chloramphenicol, neomycin, rifamycin, rifaximine, tyrothricin and/or their salts as local antibacterials. Inventive microemulsion formulation effective in wound and burn treatment in an embodiment of the invention comprises the following;

• Antibacterial fucidic acid and/or its salts in the range of 0.1-10% by weight as active substance and local anesthetic benzocaine and/or its salt in the range of 0.1-20% by weight,

• Ethyl oleate in the range of 1-30% by weight as the oil phase,

• Water in the range of 5-30% by weight as water phase,

• PEG-35 Hydrogenated Castor Oil in the range of 1-50% by weight as surfactant,

• Propylene glycol and ethanol in the ratio of 1 : 1 in the range of 5-50% by weight as the cosurfactant.

Inventive microemulsion formulation effective in wound and burn treatment in another embodiment of the invention comprises the following;

• Antibacterial fucidic acid and/or its salts in the amount of 2% by weight and local anesthetic benzocaine and/or its salt in the amount of 2% by weight as active substance,

• Ethyl oleate in the amount of 11.5% by weight as the oil phase,

• Water in the amount of 23.2% by weight as water phase,

• PEG-35 Hydrogenated castor oil in the amount of 32.2% by weight as surfactant,

• Propylene glycol and ethanol in the ratio of 1 : 1 in the amount of 32.2% by weight as cosurfactant. Of the substances that make up the microemulsion, which is the carrier system; ethyl oleate is the oil phase, cremophor is surfactant, propylene glycol and ethanol are the co-surfactant, and distilled water is the water phase. A stable microemulsion is formed since these 4 main component are in specific concentrations together. If any of these substances are removed from the formulation, microemulsion does not occur or microemulsion does not occur if they are outside the specified ratios.

It has been determined that the formulation developed in in vitro release studies has better release properties than Fucidin cream. In addition, the difference in release results compared to benzocaine solution was not statistically significant (p>0.05). 2% benzocaine solution reached a release level of 98%, while the percentage of benzocaine release from the microemulsion developed was found to be 97% according to the results of in vitro release studies conducted with the dialysis bag method for 24-hours. The percentage of release of fucidic acid from microemulsion in 24 hours was found to be 68% in the same study. On the other hand, the release of the active substance from the commercial product containing 2% fucidic acid (Fucidin cream) at the end of the same period was found to be 20% (Figure 1). The 2% benzocaine solution was prepared by dissolving 2% benzocaine by weight in ethyl oleate since there is no commercially available product on the market.

One of the most important features of microemulsions is that they penetrate the skin and do not penetrate the deep layers of the skin too much. This is a very important advantage for the formulations that are desired to show local effect. Benzocaine and fucidic acid active substances are also desired to have a local effect in the developed invention. The permeability of the microemulsion performed in the Franz Diffusion Cell system using mice skins was compared with the commercial product (Fucidin cream) and the oily solution of benzocaine (2% benzocaine solution) for this purpose. According to the results of the studies conducted for 24 hours, oily solution of benzocaine (2%) and Fucidin cream showed 18% and 1.6% permeability values (%), respectively; while in the developed microemulsion, permeability values of benzocaine and fucidic acid were found as 9.3% and 0.3%, respectively. The skin was cut into small pieces and mixed in appropriate solvents and the amount of active substance remaining in the skin was analyzed at the end of the study. It has been observed that the microemulsion formulation penetrates 1.6 times higher for benzocaine (compared to benzocaine solution) and approximately 3 times higher for fucidic acid (compared to Fucidin cream). These results show that the developed microemulsion formulation penetrates the upper layers of the skin better and will pass less into the systemic circulation.

The invention is also a method of preparing fucidic acid and benzocaine microemulsion.

A method of preparing a microemulsion formulation effective in wound and bum treatment comprises the following steps; a) First, dissolving 2% by weight of benzocaine and 2% by weight of fucidic acid, which are active substances dissolved in oil, in ethyl oleate by mixing at room temperature for 10 minutes-4 hours and at a rate of 50-1000 rpm, b) Adding 32.2% by weight of PEG-35 Hydrogenated castor oil (Cremophor EL, Polyoxyl 35 Hydrogenated Castor Oil) to the oil phase and dissolving at room temperature for 10 minutes-4 hours and at 50-1000 rpm, c) Afterward, adding 32.2% by weight of propylene glycol and ethanol (1 : 1) mixture to the cosurfactant oil phase, respectively and homogenizing by mixing in the magnetic stirrer for 10 minutes-4 hours and at a speed of 50-1000 rpm, d) Finally, adding 23.2% by weight of distilled water dropwise to the oil phase with the titration and mixing for 10 minutes-4 hours and at a speed of 50-1000 rpm method and homogenizing.

The microemulsion can be mixed for a total of 15 minutes to 24 hours in all process steps in the process. Steps a and b are carried out in the temperature range of 20-80°C. Steps c and d are carried out in the temperature range of 20-40°C. The formulation can be made gel-like by adding 0.1-20% gel -forming agent by weight after step d. Polyacrylic acid and derivative polymers, cellulose-derived polymers, alginic acid and derivative polymers or chitosan and derivative natural or synthetic polymers can be used as gel-forming agents.

Microemulsion Characterization Results

Table 1 shows the characterization results of the developed microemulsion. Table 1: Characterization of microemulsion formulations with and without the active substance developed (mean±SD, n = 5).

Formulation Microemulsion not Microemulsion containing

Parameters containing active Benzocaine and Fucidic acid substance

Particle Size (nm) 23.076±0.285 19.388±0.480

Polydispersity index 0.097±0.016 0.054 ±0.011

Zeta Potential (mV) -3.274±0.313 -3.014±1.265

Refractive Index 1.4173±0.0003 1.4266±0.0003

Conductivity (mS/cm) 0.427±0.015 0.386±0.007

Viscosity (cP) 500.800±2.490 338.400±2.074 pH 7.398±0.058 6.440±0.016