| dc.description.abstract | Intrinsic skin ageing is predominantly caused by a decrease in female hormones as menopause approaches. It is suggested that topical application of female hormones may treat these ageing symptoms. Unfortunately, the circulatory absorbance of these hormones may have damaging effects, such as triggering hormone sensitive cancers and cardiovascular incidences, which may be due to the favourable physicochemical properties that these hormones have for transdermal drug delivery.
Two formulation approaches were followed for comparison purposes via Franz cell diffusion studies. The first approach was taken by Idexis (Pty) Ltd., by formulating classified formulations (face, neck, hand and body cream) containing diffusion inhibitors (in order to hinder transdermal drug diffusion), the selected female hormones (oestriol, oestradiol and progesterone) and a wide range of antioxidants (for stability and skin care purposes). It was told that the Idexis formulation strategy was complex and expensive. The second approach was taken by formulating cost-effective, basic semi-solid formulations containing different natural oils (emu, castor and coconut oil) and the same APIs (active pharmaceutical ingredients) as those used in the Idexis formulations.
For pre-formulation purposes, three oil-in-water (o/w) semi-solids containing different excipients were formulated and characterised to determine which formulation should be used as a guideline to incorporate the hormones and natural oils. Subsequently, three formulations were formulated containing correct concentrations of hormones and natural oils. All three formulations were then characterised to determine stability status and cosmeceutical refinement in which all three met the requirements.
Membrane release studies were done on all the formulations (Idexis and custom-made) to obtain flux values, which indicated the release of the APIs from the different formulations. It was found that all formulations released the APIs, but to a lesser extent in the custom-made formulations. Skin diffusion studies (12 h) were then conducted with the formulations to analyse the API diffusion into the receptor phase to determine if transdermal drug delivery occurred. Tape stripping was performed for each formulation to determine the concentration of APIs present in each skin layer (stratum corneum-epidermis and epidermis-dermis). It was found that all formulations delivered the selected female hormones to the different skin layers (higher concentrations for the Idexis formulations), but unfortunately transdermal drug delivery occurred with the Idexis formulations, therefore the custom-made formulations achieved the aim for topical delivery.
A three-month accelerated stability study was conducted on the Idexis formulations at different climate conditions (25 °C/60% RH (relative humidity), 30 °C/65% RH and 40 °C/75% RH). Stability parameters, namely zeta-potential, particle size, pH, viscosity, mass loss, concentration assay, visual appearance and odour were measured at each time interval. The neck cream appeared to be the most stable formulation of all the Idexis formulations (possibly due to wide range and higher concentration of antioxidants used, compared to the other Idexis formulations), but eventually all the formulations tended to become unstable over time in all the aforementioned parameters, indicating further stability optimisation should occur for these formulations. | en_US |
