Researchers at Tanta University have made significant strides in the treatment of benign prostatic hyperplasia (BPH) by developing menthol-based microemulsions capable of simultaneous transdermal delivery of finasteride and silodosin, two prime medications for this condition. BPH, which predominantly affects older men, can severely disrupt urinary function, leading to incomplete bladder emptying and increased pressure on the urethra.
Traditional treatment methods for BPH typically involve oral medications, but the low bioavailability of these drugs presents challenges for effective therapy. For example, finasteride, which inhibits the enzyme responsible for converting testosterone to dihydrotestosterone (a contributor to prostate enlargement), has only about 63% absorption when taken orally. Silodosin, another favored treatment due to its selectivity and fewer side effects, shows only 32% oral bioavailability. To overcome these limitations, the researchers explored transdermal delivery systems, which could potentially improve drug absorption and efficacy.
The study pioneered the use of menthol-based microemulsions combining finasteride and silodosin, utilizing pseudoternary phase diagrams to optimize the formulation. The microemulsions were characterized for their viscosity, droplet sizes, and drug release efficacy at both room temperature and at 32 °C, simulating human skin conditions.
Findings showed promising results; the researchers reported, "simultaneous loading of finasteride and silodosin in microemulsions modulated thermodynamic activity." Specifically, microemulsions demonstrated lower drug release rates compared to saturated aqueous solutions, yet they significantly enhanced the transdermal flux of both drugs. The ethanol-containing microemulsions were particularly effective, producing the highest drug flux, underscoring the advantage of incorporating cosurfactants to facilitate skin penetration.
Characterization studies revealed the microemulsions displayed thermoresponsive behavior, transitioning from gel-like structures at lower temperatures to clear microemulsions at higher temperatures, effectively demonstrating their applicability as drug delivery systems. The viscosity of these microemulsions varied significantly with temperature, ranging from 1476 cps at room temperature for cosurfactant-free formulations to as low as 21.1 cps when ethanol was included as cosurfactant.
One of the intriguing insights was the transdermal flux of finasteride. The flux from saturated aqueous solutions was determined to be just 0.47 μg cm−2 h−1, whereas the microemulsion systems achieved continuous release, with the researchers noting, "the transdermal flux of finasteride from microemulsion formulations significantly exceeded the flux from aqueous controls."
For silodosin, the enhanced transdermal flux was also recorded, with the highest levels observed from ethanol-containing microemulsions. The combination of finasteride and silodosin did not negatively impact transdermal absorption, maintaining higher flux rates than those achieved with oral delivery methods. The outcomes of this research indicate the potential for developing effective topical therapies using the described microemulsions for simultaneous drug delivery.
Overall, this novel formulation marks promising advancements for patients suffering from BPH and offers researchers new avenues for improving the bioavailability of other medications through transdermal delivery systems. The study introduces temperature-dependent microemulsion systems as efficient tools for enhanced transdermal drug delivery.
These findings are not only relevant for improving treatment options for BPH but also raise questions on the broader application of microemulsion systems across various therapeutic areas, emphasizing the importance of innovative drug delivery methods. Future studies will be necessary to validate these results and explore the full therapeutic potential of menthol-based microemulsions.