Microemulsions: A Novel Approach to Enhanced Drug Delivery

Abstract

Microemulsions are isotropic, thermodynamically stable transparent (or translucent) systems of oil, water and surfactant, frequently in combination with a cosurfactant with a droplet size usually in the range of 20-200 nm. They can be classified as oil-in-water (o/w), water-in-oil (w/o) or bicontinuous systems depending on their structure and are characterized by ultra low interfacial tension between oil and water phases. These versatile systems are currently of great technological and scientific interest to the researchers because of their potential to incorporate a wide range of drug molecules (hydrophilic and hydrophobic) due to the presence of both lipophilic and hydrophilic domains. These adaptable delivery systems provide protection against oxidation, enzymatic hydrolysis and improve the solubilization of lipophilic drugs and hence enhance their bioavailability. In addition to oral and intravenous delivery, they are amenable for sustained and targeted delivery through ophthalmic, dental, pulmonary, vaginal and topical routes. Microemulsions are experiencing a very active development as reflected by the numerous publications and patents being granted on these systems. They have been used to improve the oral bioavailability of various poorly soluble drugs including cyclosporine and paclitaxel as professed by Hauer et al., US patent 7235248, and Gao et al., US patent 7115565, respectively. Furthermore, they can be employed for challenging tasks such as carrying chemotherapeutic agents to neoplastic cells and oral delivery of insulin as diligently described by Maranhao, US patent 5578583 and Burnside et al., US patent 5824638 respectively. The recent commercial success of Sandimmune Neoral (Cyclosporine A), Fortovase (Saquinavir), Norvir (Ritonavir), etc. also reflects the tremendous potential of these newer drug therapeutic systems. A critical evaluation of recent patents claiming different approaches to improve the drug delivery is the focus of the current review.

Study of In Vitro Drug Release and Percutaneous Absorption of Fluconazole from Topical Dosage Forms

“…The obtained results show a remarkable influence of the kind of dosage form used when a considerable absorption of drug is desirable. These results are in agreement with other authors that have also indicated the proven enhancement effect observed for microemulsions (24)(25)(26). It is also promising that the inclusion of Transcutol® enhanced topical administration, and it was observed, as other literature also reflects, that the effect of skin penetration enhancers depends on the vehicle (37).…”

Introductory Chapter: Microemulsions

“…In this case, the permeation was shown to increase when glycolipids were incorporated into the microemulsion indicating that they could outperform macroemulsions in topical drug delivery. Poorly soluble drugs such as cyclosporine and paclitaxel have shown improved oral bioavailability in microemulsion systems and have been patented along with other drugs such as ritonavir and saquinavir [28].…”

Kesan Penambahan Limonena terhadap Mikroemulsi Asid oleik/Cremophor rh 40/Transcutol/Air

“…Sistem mikroemulsi mempunyai kelebihan berbanding sistem konvensional yang sedia ada dari segi pembentukan yang spontan tanpa memerlukan tenaga yang tinggi, stabil secara termodinamik dan berupaya memperbaiki sifat keterlarutan serta bioketersediaan bahan aktif (Idress et al 2011;Talegaonkar et al 2008). Penggunaan sistem mikroemulsi sebagai sistem penghantar melalui kulit telah banyak dibangunkan oleh kerana kelebihan sistem ini di dalam meningkatkan penembusan bahan aktif hidrofobik dan hidrofilik melalui lapisan kulit (Al Abood et al 2013;Maura et al 2014;Silva et al 2013;Sintov 2015;Talegaonkar et al 2008). Komponen amfifilik di dalam sistem mikroemulsi berperanan sebagai bahan penggalak penembusan bagi sistem ini (Idress et al 2011;Som et al 2012).…”