Microemulsions as Solubilizers and Penetration Enhancers for Minoxidil Release from Gels

Abstract

Micro- and nanoemulsions are potential drug solubilizers and penetration enhancers through the high surfactant/co-surfactant content. This study aimed to evaluate the influence of minoxidil (MXD) solubilized in the microemulsions (MEs) on drug release by in vitro/ex vivo diffusion through the semi-permeable membrane Spectra/Por® (Spectrum Laboratory, Gardena, CA, USA) and porcine ear skin. Moreover, a residual amount of drug in the skin after ex vivo diffusion was evaluated. The reference MER, lecithin-containing MEL, and gelatin-containing MEG were characterized in terms of their size, polydispersity index, density, viscosity, electrical conductivity and surface tension. Based on the in vitro diffusion, it can be argued that MEL slowed down the drug release, while MER and MEG have no significant effect compared to the sample, in which propylene glycol (PG) was used as a solubilizer. Determination of the residual drug amount in the skin after 6 h of the ex vivo permeation was demonstrated as the most valuable method to evaluate the effectiveness of the ME’s application. The results indicate that the most optimal MXD permeation enhancers in alginate gel were the natural surfactants containing MEs. MXD solubilization in MEG and MEL had caused more than 5% of the drug remaining in the skin, which is almost a 1.5-fold higher amount compared to the reference gel.

Nanoemulsion-Based Hydrogels and Organogels Containing Propolis and Dexpanthenol: Preparation, Characterization, and Comparative Evaluation of Stability, Antimicrobial, and Cytotoxic Properties

“…The effect of surfactant ratios and amounts is also evident here, and as the amount increased, the conductivity decreased very little. Similar results were obtained in the studies of Špaglová et al and Hasssanzadeh et al [ 33 , 34 ]. Again, homogeneous, white, non-phase separation nanoemulsions were obtained in the dilution technique, which indicates the miscibility of the nanoemulsion with ultrapure water.…”

Insights from a Box–Behnken Optimization Study of Microemulsions with Salicylic Acid for Acne Therapy

“…Flow behavior of microemulsions was considered specific for Newtonian fluids. Values of viscosity of 22.4-26.69 cP were reported in rheological study of O/W microemulsions with minoxidil, being associated with the composition based on a total amount of S/CoS mixture of 53% [83]. As the concentration of S/CoS blend increases between 54-60%, viscosity can attain 637.47-808.20 cP, as it was observed in the evaluation process of O/W microemulsions with palm oil 6%, without changing the model of viscosity [95].…”

“…In the study of Špaglová M. et al, topical microemulsions were formulated using a reduced level of Tween 80 of 26.5% and isopropyl alcohol of 26.5%. Lecithin was selected at 0.75% and was considered one of the formulation factors that influenced the behavior of microemulsions in the process of diffusion [83].…”

Lecithins: A comprehensive review of their properties and their use in formulating microemulsions

“…For example, ketoprofen, amphotericin B, lidocaine, insulin, flufenamic acid, and fluconazole have been successfully incorporated in lecithin‐based microemulsions (Table 3). Such microemulsions have been tested as transdermal drug delivery systems by direct skin contact (Paolino et al, 2002; Schwarz et al, 2012; Yuan et al, 2008), using in situ patches (Yuan & Acosta, 2009), and applied as gels (Špaglová et al, 2021).…”