No description available.

The skin is an amazingly resilient and relatively impermeable barrier that provides protective, perceptive and communication functions to the body (Ramachandran & Fleisher, 2000). The stratum corneum is widely accepted as the barrier of the skin - limiting the transport of molecules into and across the skin. One of the bottlenecks in the successful development of transdermal drug delivery devices is the fact that the skin (more accurately, the stratum corneum - SC) tends to control the rate of drug transport. This makes it very difficult to influence or regulate the transdermal drug absorption kinetics from outside, Le. by means of the vehicle. A possible, and even elegant, solution may be the use of so-called "penetration enhancers", thereby suppressing the dominant role of the stratum corneum penetration barrier (Bodde et al., 1990). For this study 5-fluorouracil (5-FU), a polar hydrophilic drug, was chosen as model drug to study its penetration through the stratum corneum. Terpenes used as possible penetration enhancers for 5-FU were menthol, isomenthol, menthone, l3-myrcene, limonene and 1,8-cineole. In previous studies, terpenes with low skin irritancy and low systemic toxicity, were found to be effective penetration enhancers for a number of hydrophilic and lipophillic drugs (Cornwell & Barry, 1994; Cornwell et a/., 1996; Godwin & Michniak, 1999). The objective of this study was to determine the different flux rates of 5-FU in the absence of any pre-treatment of the stratum corneum and also through ethanol and selected terpene pre-treated SC. The effect of each terpene on the penetration of 5-FU was determined. The penetration of the selected terpenes themselves through the human stratum corneum was also determined in vitro permeation studies were performed using vertical Franz diffusion cells with human skin (stratum corneum). A saturated aqueous solution of 5-fluorouracil in the absence and presence of pre-treatment of the SC was used as the donor phase. Pre-treatment was performed by applying a 5 % terpene solution or absolute ethanol to the SC half an hour before the saturated III solution was applied in the donor compartment. A 50/50 ethanol/water solution was used as the receptor phase. All the experiments were conducted over a 24 h period. The 37°C temperature was held constant by means of a water bath. For the analysis of 5-FU flux rates, samples from the receptor compartment were obtained and were analysed by means of high-pressure liquid chromatography (HPLC). In order to determine the cumulative percentage of terpenes penetrated through human stratum corneum, the samples were analysed by gas chromatography (GC). In this study, only menthol and isomenthol (both oxygen-containing terpenes) showed a statistically significant increase on the flux of 5-FU, with flux values of 1.13 +- 0.38 and 1.45 +- 0.68 ug/cm2/h, respectively, compared to untreated skin with a flux value of 0.54 +- 0.23 ug/cm2/h for 5-FU. It was also proved that ethanol itself had an enhancing effect on 5-FU and showed synergistic effects on the enhancement activities of all the terpenes. It was found that all the terpenes (applied as a 5 % solution in ethanol) penetrated through the stratum corneum in the absence of 5-fluorouracil. 5-Fluorouracil had either an increasing or decreasing effect on the penetration of the terpenes. From these findings, it could be concluded that oxygen-containing terpenes had the best penetration enhancing effect on 5-FU and that menthol and isomenthol were the most effective penetration enhancers, although the extend of penetration enhancement is not large enough for clinical application. All the terpenes have the ability to penetrate through human stratum corneum, and 5-FU either had an increasing or decreasing effect on their penetration. / Thesis (M.Sc.)--North-West University, Potchefstroom Campus, 2004.

Acyclovir is an antiviral drug used in the treatment and prevention of herpes simplex and varicella-zoster viral infections. The major problem in the transdermal delivery of acyclovir is the permeation in sufficient amounts to deeper layers of the skin and into the systemic circulation. Acyclovir is a hydrophilic substance with a low partition coefficient, resulting in poor penetration through the excellent barrier of the skin, the stratum corneum. In an attempt to enhance the transdermal permeability of acyclovir, the aim of this study was to employ terpenes as possible penetration enhancers. Terpenes are constituents of natural essential oils, with widespread medicinal use including in aromatherapy. The terpenes used in this study were 1,8-cineole, limonene, menthol, menthone, and 13- myrcene. Terpenes are not only used as penetration enhancers, but are even more often present in drugs and cosmetics. Limited studies have been done concerning the penetration of terpenes through the skin. Thus, not only the effect of the terpenes on the penetration of acyclovir, but also the penetration of the terpenes themselves were studied. The influence of acyclovir on the penetration of the terpenes was also determined. In vitro permeation experiments were performed on human skin using Franz diffusion cells. The skin was pretreated with a 5 % solution of the terpene in ethanol and left for 30 minutes to enable ethanol evaporation and terpene incorporation into the skin. Saturated aqueous solutions of acyclovir (pH 7.4) were added in the donor compartment before and after skin pre-treatment. The acyclovir concentration retrieved from the receptor compartment of the Franz cells was analyzed by HPLC. The amount of terpene that penetrated were semi-quantitatively determined by GC. Penetration of acyclovir was significantly enhanced by two terpenes, viz. 1,8-cineole and menthol. The extent of enhancement was, however, not large enough to be of clinical use. The enhancement in acyclovir penetration observed upon ethanol pre-treatment alone, or in the presence of limonene, menthone or ~-myrcene, was not significant. Penetration enhancement of acyclovir by the terpenes was in accordance with previous studies, which postulated better enhancement of hydrophilic drugs by hydrophilic terpenes. Large percentages of the terpenes with log P values within the optimum log P range (1 - 3) penetrated, as was found with menthone and menthol. Penetration decreased accordingly as the log P, and thus lipophilicity, increased. Stratum corneum retention is regarded as the most plausible explanation for this phenomenon. In the case of 1,8- cineole, enhancer pooling in the stratum corneum could be a possible reason for its poor penetration. Acyclovir significantly influenced the penetration profiles of some of the terpenes, but no clear explanation could be given. / Thesis (M.Sc. (Pharm.))--North-West University, Potchefstroom Campus, 2004.

The skin is an amazingly resilient and relatively impermeable barrier that provides protective, perceptive and communication functions to the body (Ramachandran & Fleisher, 2000). The stratum corneum is widely accepted as the barrier of the skin - limiting the transport of molecules into and across the skin. One of the bottlenecks in the successful development of transdermal drug delivery devices is the fact that the skin (more accurately, the stratum corneum - SC) tends to control the rate of drug transport. This makes it very difficult to influence or regulate the transdermal drug absorption kinetics from outside, Le. by means of the vehicle. A possible, and even elegant, solution may be the use of so-called "penetration enhancers", thereby suppressing the dominant role of the stratum corneum penetration barrier (Bodde et al., 1990). For this study 5-fluorouracil (5-FU), a polar hydrophilic drug, was chosen as model drug to study its penetration through the stratum corneum. Terpenes used as possible penetration enhancers for 5-FU were menthol, isomenthol, menthone, l3-myrcene, limonene and 1,8-cineole. In previous studies, terpenes with low skin irritancy and low systemic toxicity, were found to be effective penetration enhancers for a number of hydrophilic and lipophillic drugs (Cornwell & Barry, 1994; Cornwell et a/., 1996; Godwin & Michniak, 1999). The objective of this study was to determine the different flux rates of 5-FU in the absence of any pre-treatment of the stratum corneum and also through ethanol and selected terpene pre-treated SC. The effect of each terpene on the penetration of 5-FU was determined. The penetration of the selected terpenes themselves through the human stratum corneum was also determined in vitro permeation studies were performed using vertical Franz diffusion cells with human skin (stratum corneum). A saturated aqueous solution of 5-fluorouracil in the absence and presence of pre-treatment of the SC was used as the donor phase. Pre-treatment was performed by applying a 5 % terpene solution or absolute ethanol to the SC half an hour before the saturated III solution was applied in the donor compartment. A 50/50 ethanol/water solution was used as the receptor phase. All the experiments were conducted over a 24 h period. The 37°C temperature was held constant by means of a water bath. For the analysis of 5-FU flux rates, samples from the receptor compartment were obtained and were analysed by means of high-pressure liquid chromatography (HPLC). In order to determine the cumulative percentage of terpenes penetrated through human stratum corneum, the samples were analysed by gas chromatography (GC). In this study, only menthol and isomenthol (both oxygen-containing terpenes) showed a statistically significant increase on the flux of 5-FU, with flux values of 1.13 +- 0.38 and 1.45 +- 0.68 ug/cm2/h, respectively, compared to untreated skin with a flux value of 0.54 +- 0.23 ug/cm2/h for 5-FU. It was also proved that ethanol itself had an enhancing effect on 5-FU and showed synergistic effects on the enhancement activities of all the terpenes. It was found that all the terpenes (applied as a 5 % solution in ethanol) penetrated through the stratum corneum in the absence of 5-fluorouracil. 5-Fluorouracil had either an increasing or decreasing effect on the penetration of the terpenes. From these findings, it could be concluded that oxygen-containing terpenes had the best penetration enhancing effect on 5-FU and that menthol and isomenthol were the most effective penetration enhancers, although the extend of penetration enhancement is not large enough for clinical application. All the terpenes have the ability to penetrate through human stratum corneum, and 5-FU either had an increasing or decreasing effect on their penetration. / Thesis (M.Sc.)--North-West University, Potchefstroom Campus, 2004.

Acyclovir is an antiviral drug used in the treatment and prevention of herpes simplex and varicella-zoster viral infections. The major problem in the transdermal delivery of acyclovir is the permeation in sufficient amounts to deeper layers of the skin and into the systemic circulation. Acyclovir is a hydrophilic substance with a low partition coefficient, resulting in poor penetration through the excellent barrier of the skin, the stratum corneum. In an attempt to enhance the transdermal permeability of acyclovir, the aim of this study was to employ terpenes as possible penetration enhancers. Terpenes are constituents of natural essential oils, with widespread medicinal use including in aromatherapy. The terpenes used in this study were 1,8-cineole, limonene, menthol, menthone, and 13- myrcene. Terpenes are not only used as penetration enhancers, but are even more often present in drugs and cosmetics. Limited studies have been done concerning the penetration of terpenes through the skin. Thus, not only the effect of the terpenes on the penetration of acyclovir, but also the penetration of the terpenes themselves were studied. The influence of acyclovir on the penetration of the terpenes was also determined. In vitro permeation experiments were performed on human skin using Franz diffusion cells. The skin was pretreated with a 5 % solution of the terpene in ethanol and left for 30 minutes to enable ethanol evaporation and terpene incorporation into the skin. Saturated aqueous solutions of acyclovir (pH 7.4) were added in the donor compartment before and after skin pre-treatment. The acyclovir concentration retrieved from the receptor compartment of the Franz cells was analyzed by HPLC. The amount of terpene that penetrated were semi-quantitatively determined by GC. Penetration of acyclovir was significantly enhanced by two terpenes, viz. 1,8-cineole and menthol. The extent of enhancement was, however, not large enough to be of clinical use. The enhancement in acyclovir penetration observed upon ethanol pre-treatment alone, or in the presence of limonene, menthone or ~-myrcene, was not significant. Penetration enhancement of acyclovir by the terpenes was in accordance with previous studies, which postulated better enhancement of hydrophilic drugs by hydrophilic terpenes. Large percentages of the terpenes with log P values within the optimum log P range (1 - 3) penetrated, as was found with menthone and menthol. Penetration decreased accordingly as the log P, and thus lipophilicity, increased. Stratum corneum retention is regarded as the most plausible explanation for this phenomenon. In the case of 1,8- cineole, enhancer pooling in the stratum corneum could be a possible reason for its poor penetration. Acyclovir significantly influenced the penetration profiles of some of the terpenes, but no clear explanation could be given. / Thesis (M.Sc. (Pharm.))--North-West University, Potchefstroom Campus, 2004.

The molecular basis of the potent transdermal enhancement activity of a series of iminosulfuranes, structure provided where X = H, Cl, Br, and I, is being investigated skin models. It has been shown (J. Lipid Res. 46(2005), 2192-2201.) that correlations exist between the activity of the aforementioned transdermal penetration enhancers (TPE) and the extent to which these agents bind to DMPC vesicles and perturb the gel to liquid crystal phase transition measured by calorimetry. The degree to which the perturbation of these compounds extends into the bilayer interior in contrast to surface activity is unclear. To gain insight into this issue, the 31P NMR resonance from DMPC and DMPC-cholesterol unilamellar vesicles have been split by the slowly penetrating paramagnetic metal ion Pr+3. The extent to which this perturbation is attenuated by transdermal penetration enhancers has been investigated as a function of Pr+3 exposure time and iminosulfurane concentration. The effect of these iminosulfuranes on bilayer integrity is also being explored by monitoring the induced release of carboxyfluorescein from DMPC and DMPC- cholesterol unilamellar vesicles.

Charles University, Faculty of Pharmacy in Hradec Králové Department of Pharmaceutical Technology Author: Petr Tirala Supervisor: PharmDr. Barbora Švecová, Ph.D. Title of thesis: Formulation and (trans)dermal application of liposomes containing imiquimod Imiquimod (IMQ), a substance belonging to the class of heterocyclic imidazoquinolines, shows significant immunomodulatory effects after topical administration, which is used to treat a variety of viral and malignant diseases of the skin. IMQ is currently used in clinical practice in the form of cream Aldara® containing 5% of active substance, which is unstable and irritating and after removal from the skin IMQ poses an ecological load for the environment. The aim of this thesis was preparation of liposomes for topical administrativ containing lower - 1% amount of IMQ and evaluation of penetration of IMQ into human skin in vitro. To improve the properties of liposomes and promote patency of the active ingredient through the skin barrier to the deeper skin layers various additives were used. Permeation experiments were carried out in Franz diffusion cells on the human skin in order to create the conditions that are as physiological as possible. Amount of IMQ was determined in the uppermost layer of the skin, epidermis, dermis, acceptor phase...

Onychomycosis also known as dermatophytic onychomycosis is the fungal infection of the toenails and fingernails, characterized by discoloration and thickening of the nail and involves the nail plate, nail bed and nail folds. The disease is more than a cosmetic problem, as it severely impacts the patient's quality of life. Onychomycosis is an opportunistic infection in special subpopulations of patients suffering from diabetes, psoriasis, HIV/AIDS etc. The current treatment strategies involve systemic delivery of oral antifungal agents including azoles (e.g. itraconazole) and allylamines (e.g. terbinafine hydrochloride) which are delivered to the nail plate from the nail bed. More recently, topical delivery of drugs including amorolfine and bifonazole/urea (available outside the United States) and Penlac® nail lacquer (ciclopirox) topical solution, 8%, available in the US are an alternative treatment option to the oral antifungal agents. Topical delivery of antifungal agents through the human nail offer several advantages over oral therapy including lower incidence of adverse events and lower potential for drug-drug interaction with drugs used to treat diabetes, HIV/AIDS and psoriasis. The objectives of this project were to: 1) To determine the critical factors affecting the delivery of ciclopirox olamine across the human nail, 2) To screen and select penetration enhancer(s) specific for ciclopirox olamine delivery into the target tissue(s) and 3) To develop a novel transungual formulation containing ciclopirox olamine (CPO) and penetration enhancer(s) for transungual delivery. Ciclopirox olamine, the salt form of the free acid of ciclopirox was used in the study to develop a novel transungual patch formulation and skin and nail permeation from the patch formulation was compared to Penlac® nail lacquer. Various factors such as drug partitioning into the healthy and infected toenail, drug-keratin binding, lateral diffusion, drug-epidermal binding and the formulation components, all play a role in achieving optimum drug penetration and permeation through the nail. Understanding the interplay of these factors helped in the development of an effective topical formulation which was observed to be superior to Penlac® nail lacquer in the in vitro studies. Most cases of onychomycosis show infection and inflammation of the nail folds (skin surrounding the nails). Therefore for an efficient treatment of OM, the antifungal drugs must be delivered to two target tissues - human nail and the nail folds. The major challenges in developing a topical formulation for treatment on OM are: a) Achieving antifungal drug minimum inhibitory concentration (MIC) in the epidermis of the nail folds. b) Enhancing penetration and permeation of the antifungal drug across the human nail to reach the nail bed and achieve the necessary MIC (tissue underneath the nail). Twelve chemical penetration enhancers (PEs) were screened for their ability to enhance ciclopirox olamine accumulation into the nail folds and permeation through the nail. Propylene glycol (PG) enhanced the levels of the drug in the epidermis of the skin while limiting its permeation across the skin. Thiourea (TU) was selected as the best enhancer to increase ciclopirox olamine penetration into the nail. The diffusion of the antifungal drug across the human nail was studied in vitro using human cadaver toenails mounted in Franz diffusion cells. Pressure sensitive adhesives (PSA) belonging to the polyisobutylene, polysiloxane and polyacrylate classes of adhesives were screened to develop a monolithic drug-in-adhesive-type nail patch. The in vitro release of CPO from the PSA patches were limited and did not improve in presence of hydrophilic plasticizer (propylene glycol) and hydrophobic plasticizers (triacetin and triethyl citrate). Increasing the concentration of TU from 1 % to 10 %, lead to its crystallization in the dry patches. Therefore a change in the patch design was recommended. Other hydrophilic polymers including Polyoxyethylene (POLYOX®) and hydroxyl propyl methyl cellulose (HPMC) were also screened to develop a modified drug-in-hydrophilic matrix patch design. The patch was designed to incorporate CPO, PG and TU in the polymer matrix overlaid on a non-occlusive backing membrane cast with polyacrylate PSA. The HPMC films showed the best drug release profile with 80 % release in 2 to 4 hours using a USP apparatus 5. These patches were characterized for drug penetration into the skin and nail permeation. Penlac® nail lacquer was used as the comparator control product. The prototype HPMC K15M patch containing 10 %w/w each of the drug and TU and 150 % w/w of PG showed 2.8 fold increase in CPO accumulation in epidermis compared to Penlac® nail lacquer in 24 hours. The skin permeation was found to be similar to that of Penlac®. The HPMC K15M patch formulation showed 2.7 fold increase in CPO concentration within the nail and 4.2 fold increase in transungual flux compared to Penlac®. The patch delivered higher levels of ciclopirox olamine into the target tissues with a lower permeation lag-time. The novel nail patch delivery system had the following properties: a) Ease of application, b) Contact with the nail surface, c) Increased concentration of drug in dissolved form within the patch, d) Presence of enhancers. The novel nail patch formulation has shown increased efficiency in topical and transungual drug delivery for treatment of OM, when compared to the commercial formulation, Penlac® nail lacquer in the in vitro studies. The physical characterization of the patch using Scanning Electron Microscopy, Polarized Light Microscopy, Optical Light Microscopy, Differential Scanning Calorimetry, X-Ray Diffractometer and Fourier Transform Infrared Spectroscopy show that ciclopirox olamine exists at a sub-saturation level in a non-crystalline form in the patch without any significant drug-polymer interaction. In conclusion, all the objectives of the study were met by successfully selecting penetration enhancers for CPO delivery into the nail folds and across the nail plate, evaluating the interaction between CPO and target tissues, developing a transungual patch system and characterizing the novel transungual patch. / Pharmaceutical Sciences

In pharmaceutical sciences, topical delivery is a transport process of an active pharmaceutical ingredient (API) from a formulated dosage form to the target site of action. For most topical delivery systems, the skin surface, or the specific skin layers, such as the outermost layer of the stratum corneum, the lipids amid the corneocytes within the stratum corneum, the corneocytes themselves, the epidermis, dermis, Langerhans cells, Merckle cells or the appendageal structures can be the target delivery location. When an API is delivered to the skin, it has to firstly diffuse from the formulation in which it is applied, to the skin surface. From there the API may partition into the stratum corneum, permeate across the stratum corneum and partition into the viable epidermis, from where it may partition further into the dermis and permeate across the dermis into the bloodstream (Wiechers, 2008:1-3, 7). With respect to the barrier function of the skin, the intercellular spaces within the stratum corneum contain lipids and its main purpose is to operate as a barrier to water-loss and to provide an imperative diffusional barrier to the absorption of APIs. This resistance is comprised of a complex interaction of lipids that creates a hydrophilic and lipophilic penetration pathway. The fundamental aspect underlying the impermeability of the skin, therefore, is the lipophilic nature of the stratum corneum (Bouwstra et al., 2003:4; Franz & Lehman, 2000:25; Walker & Smith, 1996:296). A common approach for the promotion of poorly penetrating APIs in transdermal delivery is the incorporation of chemical penetration enhancers in delivery systems, in order to promote the partitioning of an API into the stratum corneum. These chemicals are also referred to as accelerants, promoters and absorption promoters. Penetration enhancers are added to topical formulations and usually also partition into the stratum corneum, where they temporarily and reversibly disrupt its fundamental diffusional barrier properties, hence facilitating the absorption of an API through the skin (Büyüktimkin et al., 1997:358-359; Sinha & Kaur, 2000:1131; Walker & Smith, 1996:296). The mechanisms for the enhancement of diffusion of the API should therefore increase the solubility and partitioning of the drug from the formulation into the skin. It should further increase the solubility of the API within the skin and promote its permeability and diffusion coefficient (Rajadhyaksha et al., 1997:489). Fatty acids are recognised to effectively enhance the penetration of transdermally delivered hydrophilic and lipophilic APIs. Many penetration enhancers contain saturated and unsaturated hydrocarbon chains, and a popular fatty acid that has been used in this regard is oleic acid (Williams & Barry, 2004:609-610). It is believed that fatty acids disrupt the lipid organisation of the intercellular lipids within the stratum corneum to cause fluidisation of these bilayers, making the stratum corneum more permeable to APIs. Excipients with polar (hydrophilic) head groups and long hydrophobic chains i.e. fatty acids, can penetrate into the intercellular lipids of the stratum corneum and disrupt these endogenous lipid components, thereby increasing diffusion of an API within the skin (Barry, 2006:9-10; Hadgraft & Finnin, 2006:367-368; Kanikkannan et al., 2006:18; Williams & Barry, 2004:610). Natural oils are widely used in topical formulations and were an obvious choice in this study. Oils are liquids at room temperature, whereas fats are in solid form. They are relatively easy to obtain from both plants and animals. The main constituents of fats and oils are triglycerides comprising of fatty acids and a glycerol. Oils control the evaporation of moisture from the skin, spread easily and evenly and are partly metabolised in the skin to release valuable fatty acids (Fang et al., 2004:170,173; Lautenschläger, 2004:46; Mitsui, 1997:121-122). The focus of this study was not formulation per se, but included the formulation of avocado-, grapeseed-, emu-, crocodile, olive and coconut oil into semisolid emulgel- and two foam formulations. This was done in order to investigate the penetration enhancing properties of their fatty acid content on flurbiprofen which was chosen as the marker API. The emulgels containing the natural oils were compared to the same emulgel formulation containing liquid paraffin, and a hydrogel without the inclusion of an oil. Six natural oils were analysed by gas chromatography (GC) in order to quantify their fatty acid compositions, whilst also providing qualitative information by indicating the retention times of the materials with an alkyl chain composition (Mitsui, 1997:260). Data obtained with the GC indicated that olive- (76%), avocado- (68%), emu- (46%) and crocodile oil (40%) presented with high levels of oleic acid, also known as a mono-unsaturated fatty acid (MUFA). Lower levels of oleic acid were observed within grapeseed- (27%) and coconut oil (8%). The only oil demonstrating high levels of the poly-unsaturated fatty acid (PUFA), linoleic acid, was grapeseed oil (61%), whereas the remainder of the oils showed levels below 24%. Contrary, coconut oil seemed to have been the only oil high in saturated fatty acids (SFAs) and consisted of a lauric acid content of 52% and medium levels of myristic acid (21%). Average levels of palmitic acid (SFA) were found in crocodile- (21%) and in emu oil (21%), both of animal origin, whereas avocado-, grapeseed-, olive- and coconut oils from plants presented with levels below 15%. Stearic acid was also present in levels below 10% in all of these oils, with the oils of animal origin portraying the highest values. A method was developed and validated to determine the concentration of the marker flurbiprofen after diffusion from the formulations into the skin, as well as concentrations of the marker that diffused through the skin, by means of high performance liquid chromatography (HPLC). Franz cell membrane diffusion studies were conducted prior to the skin diffusion studies in order to verify the actual release of the marker from the semisolid formulations. Skin diffusion experiments were performed using dermatomed excised, human skin to which the six emulgel formulations, containing the natural oils, were applied. A comparative study was performed utilising liquid paraffin and a hydrogel, in order to compare the diffusion of the marker, flurbiprofen, into and through the skin. The two oil emulgel formulations that had indicated the best flux values were subsequently formulated into foam preparations in order to compare the penetration enhancement properties on flurbiprofen of these two oils in a foam preparation, to those in the equivalent emulgels. The data generated for all ten the formulations were compared, and the formulations that yielded the best results with regards to median flux values and the flurbiprofen concentrations within the stratum corneum-epidermis and epidermis-dermis, were identified. Application of the liquid paraffin emulgel (21.29 μg/ml) depicted the highest average concentration of the diffused lipophilic flurbiprofen within the stratum corneum-epidermis, followed by the olive oil foam (21.47 μg/ml), olive oil emulgel (17.82 μg/ml) and grapeseed oil emulgel (17.78 μg/ml). Very similar concentrations for the marker were demonstrated by the hydrogel (16.73 μg/ml) and crocodile oil emulgel (14.89 μg/ml), whereas a lower concentration was shown for coconut oil emulgel (7.18 μg/ml). The remainder of the formulations yielded concentrations below 3%, i.e. the avocado oil emulgel (2.72 μg/ml), the coconut oil foam (1.57 μg/ml) and finally the emu oil emulgel (1.25 μg/ml). The penetration of the marker, flurbiprofen, being trapped within the skin seemed to have been enhanced more by the oleic acid (UFA) containing emulgels and foam, especially. This was followed by oils containing high linoleic acid values, which indicated that the more kinked shaped the fatty acids, the more difficult it became to insert themselves within the lipid structures of the stratum corneum, with a resulting accumulation of the marker (Fang et al., 2003:318-319). It therefore seemed that those oils that predominantly consisted of unsaturated fatty acids (UFAs) (grapeseed-, crocodile- and olive oils) seemed to have increased the concentration of the diffused marker more significantly than those oils containing an almost even combination of MUFAs and PUFAs (avocado oil), or those mainly consisting of SFAs (coconut oil). Average concentrations of the diffused flurbiprofen found in the epidermis-dermis region of the skin for all of the formulations demonstrated low concentrations, ranging between 0.97 - 5.39 μg/ml, with the exception of the emu oil emulgel that presented with a higher concentration of 16.15 μg/ml. The reason for the high accumulation of the marker might have been as a result of epidermal proliferation, with subsequent accumulation of the marker within the epidermis-dermis due to high oleic- and linoleic acid values, as well as small amounts of palmitoleic acid present within this oil (Katsuta et al., 2005:1011). The resistance of the epidermis-dermis region to the general permeation of flurbiprofen might have been caused by its lipophilic nature, resulting in a reduced solubility within the hydrophilic environment of this region (Hadgraft, 1999:5). Median results from the skin diffusion studies demonstrated that the hydrogel (23.79 μg/cm2.h) had the highest flux, followed by the olive oil- (17.99 μg/cm2.h), liquid paraffin- (15.70 μg/cm2.h), coconut oil- (13.16 μg/cm2.h), grapeseed oil- (11.85 μg/cm2.h), avocado oil- (8.31 μg/cm2.h), crocodile oil- (6.68 μg/cm2.h) and emu oil emulgels (4.41 μg/cm2.h). The fact that the hydrogel presented a higher flux value for the marker could have been as a result of its high water content that had caused hydration of the skin. Hydration opens up the dense lipid structures inside of the stratum corneum, due to swelling of the corneocytes, with a subsequent increase in the marker‘s flux (Benson, 2005:28; Ranade & Hollinger, 2004:213). The high flux value of flurbiprofen with the liquid paraffin emulgel might also have resulted from the fact that it occluded the skin, which increased the hydration of the stratum corneum, with a subsequent increase in the flux (Mitsui, 1997:124; Thomas & Finnin, 2004:699). Results from the skin diffusion studies could be explained by the fact that the fatty acids differ in their hydrocarbon chain by (1) the length of the chain, and (2) the position- and number of the double bonds (Babu et al., 2006:144). It is suggested that fatty acids with hydrocarbon (lipophilic) chains between C12 to C14 (also present within coconut oil) have an optimal balance of the partition coefficient and its affinity for the skin (Ogiso & Shintani, 1990:1067). It appears as though the branched UFAs, especially oleic acid, present in high quantities in olive oil, were more powerful enhancers of the diffusion of the marker, flurbiprofen (Chi et al., 1995:270). Foam formulations were manufactured with the olive- and coconut oil emulgels that had demonstrated the best median flux values of flurbiprofen from the natural oil emulgel formulations. These formulated foams, however, did not significantly increased flux values for flurbiprofen through the skin, but only achieved values of 5.56 μg/cm2.h for the olive oil foam and 4.36 μg/cm2.h for the coconut oil foam formulations. The low flux values could have been attributed to the nature of the formulation itself, which was filled with trapped air that could have resulted in the formulation not making optimal direct contact with the available skin surface. Throughout this study, it became evident that olive oil, predominantly consisting of oleic acid (UFA), was most effective in enhancing the flux of the lipophilic marker, flurbiprofen, through the skin, closely followed by coconut oil consisting of SFAs, with lauric- and myristic acid as its main constituents. Better enhancement effects were observed with those oils containing high amounts of oleic acid (MUFA), than oils consisting of almost equal amounts of both PUFAs and MUFAs (avocado-, emu- and crocodile oil), or oils mainly consisting of PUFAs (grapeseed oil) as its main components, but their effect was not more significant than the oil containing SFAs (coconut oil) as its key components. / Thesis (MSc (Pharmaceutics))--North-West University, Potchefstroom Campus, 2013.

In pharmaceutical sciences, topical delivery is a transport process of an active pharmaceutical ingredient (API) from a formulated dosage form to the target site of action. For most topical delivery systems, the skin surface, or the specific skin layers, such as the outermost layer of the stratum corneum, the lipids amid the corneocytes within the stratum corneum, the corneocytes themselves, the epidermis, dermis, Langerhans cells, Merckle cells or the appendageal structures can be the target delivery location. When an API is delivered to the skin, it has to firstly diffuse from the formulation in which it is applied, to the skin surface. From there the API may partition into the stratum corneum, permeate across the stratum corneum and partition into the viable epidermis, from where it may partition further into the dermis and permeate across the dermis into the bloodstream (Wiechers, 2008:1-3, 7). With respect to the barrier function of the skin, the intercellular spaces within the stratum corneum contain lipids and its main purpose is to operate as a barrier to water-loss and to provide an imperative diffusional barrier to the absorption of APIs. This resistance is comprised of a complex interaction of lipids that creates a hydrophilic and lipophilic penetration pathway. The fundamental aspect underlying the impermeability of the skin, therefore, is the lipophilic nature of the stratum corneum (Bouwstra et al., 2003:4; Franz & Lehman, 2000:25; Walker & Smith, 1996:296). A common approach for the promotion of poorly penetrating APIs in transdermal delivery is the incorporation of chemical penetration enhancers in delivery systems, in order to promote the partitioning of an API into the stratum corneum. These chemicals are also referred to as accelerants, promoters and absorption promoters. Penetration enhancers are added to topical formulations and usually also partition into the stratum corneum, where they temporarily and reversibly disrupt its fundamental diffusional barrier properties, hence facilitating the absorption of an API through the skin (Büyüktimkin et al., 1997:358-359; Sinha & Kaur, 2000:1131; Walker & Smith, 1996:296). The mechanisms for the enhancement of diffusion of the API should therefore increase the solubility and partitioning of the drug from the formulation into the skin. It should further increase the solubility of the API within the skin and promote its permeability and diffusion coefficient (Rajadhyaksha et al., 1997:489). Fatty acids are recognised to effectively enhance the penetration of transdermally delivered hydrophilic and lipophilic APIs. Many penetration enhancers contain saturated and unsaturated hydrocarbon chains, and a popular fatty acid that has been used in this regard is oleic acid (Williams & Barry, 2004:609-610). It is believed that fatty acids disrupt the lipid organisation of the intercellular lipids within the stratum corneum to cause fluidisation of these bilayers, making the stratum corneum more permeable to APIs. Excipients with polar (hydrophilic) head groups and long hydrophobic chains i.e. fatty acids, can penetrate into the intercellular lipids of the stratum corneum and disrupt these endogenous lipid components, thereby increasing diffusion of an API within the skin (Barry, 2006:9-10; Hadgraft & Finnin, 2006:367-368; Kanikkannan et al., 2006:18; Williams & Barry, 2004:610). Natural oils are widely used in topical formulations and were an obvious choice in this study. Oils are liquids at room temperature, whereas fats are in solid form. They are relatively easy to obtain from both plants and animals. The main constituents of fats and oils are triglycerides comprising of fatty acids and a glycerol. Oils control the evaporation of moisture from the skin, spread easily and evenly and are partly metabolised in the skin to release valuable fatty acids (Fang et al., 2004:170,173; Lautenschläger, 2004:46; Mitsui, 1997:121-122). The focus of this study was not formulation per se, but included the formulation of avocado-, grapeseed-, emu-, crocodile, olive and coconut oil into semisolid emulgel- and two foam formulations. This was done in order to investigate the penetration enhancing properties of their fatty acid content on flurbiprofen which was chosen as the marker API. The emulgels containing the natural oils were compared to the same emulgel formulation containing liquid paraffin, and a hydrogel without the inclusion of an oil. Six natural oils were analysed by gas chromatography (GC) in order to quantify their fatty acid compositions, whilst also providing qualitative information by indicating the retention times of the materials with an alkyl chain composition (Mitsui, 1997:260). Data obtained with the GC indicated that olive- (76%), avocado- (68%), emu- (46%) and crocodile oil (40%) presented with high levels of oleic acid, also known as a mono-unsaturated fatty acid (MUFA). Lower levels of oleic acid were observed within grapeseed- (27%) and coconut oil (8%). The only oil demonstrating high levels of the poly-unsaturated fatty acid (PUFA), linoleic acid, was grapeseed oil (61%), whereas the remainder of the oils showed levels below 24%. Contrary, coconut oil seemed to have been the only oil high in saturated fatty acids (SFAs) and consisted of a lauric acid content of 52% and medium levels of myristic acid (21%). Average levels of palmitic acid (SFA) were found in crocodile- (21%) and in emu oil (21%), both of animal origin, whereas avocado-, grapeseed-, olive- and coconut oils from plants presented with levels below 15%. Stearic acid was also present in levels below 10% in all of these oils, with the oils of animal origin portraying the highest values. A method was developed and validated to determine the concentration of the marker flurbiprofen after diffusion from the formulations into the skin, as well as concentrations of the marker that diffused through the skin, by means of high performance liquid chromatography (HPLC). Franz cell membrane diffusion studies were conducted prior to the skin diffusion studies in order to verify the actual release of the marker from the semisolid formulations. Skin diffusion experiments were performed using dermatomed excised, human skin to which the six emulgel formulations, containing the natural oils, were applied. A comparative study was performed utilising liquid paraffin and a hydrogel, in order to compare the diffusion of the marker, flurbiprofen, into and through the skin. The two oil emulgel formulations that had indicated the best flux values were subsequently formulated into foam preparations in order to compare the penetration enhancement properties on flurbiprofen of these two oils in a foam preparation, to those in the equivalent emulgels. The data generated for all ten the formulations were compared, and the formulations that yielded the best results with regards to median flux values and the flurbiprofen concentrations within the stratum corneum-epidermis and epidermis-dermis, were identified. Application of the liquid paraffin emulgel (21.29 μg/ml) depicted the highest average concentration of the diffused lipophilic flurbiprofen within the stratum corneum-epidermis, followed by the olive oil foam (21.47 μg/ml), olive oil emulgel (17.82 μg/ml) and grapeseed oil emulgel (17.78 μg/ml). Very similar concentrations for the marker were demonstrated by the hydrogel (16.73 μg/ml) and crocodile oil emulgel (14.89 μg/ml), whereas a lower concentration was shown for coconut oil emulgel (7.18 μg/ml). The remainder of the formulations yielded concentrations below 3%, i.e. the avocado oil emulgel (2.72 μg/ml), the coconut oil foam (1.57 μg/ml) and finally the emu oil emulgel (1.25 μg/ml). The penetration of the marker, flurbiprofen, being trapped within the skin seemed to have been enhanced more by the oleic acid (UFA) containing emulgels and foam, especially. This was followed by oils containing high linoleic acid values, which indicated that the more kinked shaped the fatty acids, the more difficult it became to insert themselves within the lipid structures of the stratum corneum, with a resulting accumulation of the marker (Fang et al., 2003:318-319). It therefore seemed that those oils that predominantly consisted of unsaturated fatty acids (UFAs) (grapeseed-, crocodile- and olive oils) seemed to have increased the concentration of the diffused marker more significantly than those oils containing an almost even combination of MUFAs and PUFAs (avocado oil), or those mainly consisting of SFAs (coconut oil). Average concentrations of the diffused flurbiprofen found in the epidermis-dermis region of the skin for all of the formulations demonstrated low concentrations, ranging between 0.97 - 5.39 μg/ml, with the exception of the emu oil emulgel that presented with a higher concentration of 16.15 μg/ml. The reason for the high accumulation of the marker might have been as a result of epidermal proliferation, with subsequent accumulation of the marker within the epidermis-dermis due to high oleic- and linoleic acid values, as well as small amounts of palmitoleic acid present within this oil (Katsuta et al., 2005:1011). The resistance of the epidermis-dermis region to the general permeation of flurbiprofen might have been caused by its lipophilic nature, resulting in a reduced solubility within the hydrophilic environment of this region (Hadgraft, 1999:5). Median results from the skin diffusion studies demonstrated that the hydrogel (23.79 μg/cm2.h) had the highest flux, followed by the olive oil- (17.99 μg/cm2.h), liquid paraffin- (15.70 μg/cm2.h), coconut oil- (13.16 μg/cm2.h), grapeseed oil- (11.85 μg/cm2.h), avocado oil- (8.31 μg/cm2.h), crocodile oil- (6.68 μg/cm2.h) and emu oil emulgels (4.41 μg/cm2.h). The fact that the hydrogel presented a higher flux value for the marker could have been as a result of its high water content that had caused hydration of the skin. Hydration opens up the dense lipid structures inside of the stratum corneum, due to swelling of the corneocytes, with a subsequent increase in the marker‘s flux (Benson, 2005:28; Ranade & Hollinger, 2004:213). The high flux value of flurbiprofen with the liquid paraffin emulgel might also have resulted from the fact that it occluded the skin, which increased the hydration of the stratum corneum, with a subsequent increase in the flux (Mitsui, 1997:124; Thomas & Finnin, 2004:699). Results from the skin diffusion studies could be explained by the fact that the fatty acids differ in their hydrocarbon chain by (1) the length of the chain, and (2) the position- and number of the double bonds (Babu et al., 2006:144). It is suggested that fatty acids with hydrocarbon (lipophilic) chains between C12 to C14 (also present within coconut oil) have an optimal balance of the partition coefficient and its affinity for the skin (Ogiso & Shintani, 1990:1067). It appears as though the branched UFAs, especially oleic acid, present in high quantities in olive oil, were more powerful enhancers of the diffusion of the marker, flurbiprofen (Chi et al., 1995:270). Foam formulations were manufactured with the olive- and coconut oil emulgels that had demonstrated the best median flux values of flurbiprofen from the natural oil emulgel formulations. These formulated foams, however, did not significantly increased flux values for flurbiprofen through the skin, but only achieved values of 5.56 μg/cm2.h for the olive oil foam and 4.36 μg/cm2.h for the coconut oil foam formulations. The low flux values could have been attributed to the nature of the formulation itself, which was filled with trapped air that could have resulted in the formulation not making optimal direct contact with the available skin surface. Throughout this study, it became evident that olive oil, predominantly consisting of oleic acid (UFA), was most effective in enhancing the flux of the lipophilic marker, flurbiprofen, through the skin, closely followed by coconut oil consisting of SFAs, with lauric- and myristic acid as its main constituents. Better enhancement effects were observed with those oils containing high amounts of oleic acid (MUFA), than oils consisting of almost equal amounts of both PUFAs and MUFAs (avocado-, emu- and crocodile oil), or oils mainly consisting of PUFAs (grapeseed oil) as its main components, but their effect was not more significant than the oil containing SFAs (coconut oil) as its key components. / Thesis (MSc (Pharmaceutics))--North-West University, Potchefstroom Campus, 2013.