"MEs are thermodynamically stable-phase transition systems, which possess low surface tension and small droplet size (5–200 nm), which may result in high drug absorption and permeation, and hence, strong possibility of drug delivery to the posterior segment of the eye. The term ME was first coined by Hoar and Schulman in 1943 . Scientifically, a ME is a system of water, oil, and an amphiphile, frequently in combination with a cosurfactant, which is a single optically isotropic and thermodynamically stable liquid solution . "
[Show abstract][Hide abstract] ABSTRACT: Delivery of drugs into eyes using conventional drug delivery systems, such as solutions, is a considerable challenge to the treatment of ocular diseases. Drug loss from the ocular surface by lachrymal fluid secretion, lachrymal fluid-eye barriers, and blood-ocular barriers are main obstacles. A number of ophthalmic drug delivery carriers have been made to improve the bioavailability and to prolong the residence time of drugs applied topically onto the eye. The potential use of microemulsions as an ocular drug delivery carrier offers several favorable pharmaceutical and biopharmaceutical properties such as their excellent thermodynamic stability, phase transition to liquid-crystal state, very low surface tension, and small droplet size, which may result in improved ocular drug retention, extended duration of action, high ocular absorption, and permeation of loaded drugs. Further, both lipophilic and hydrophilic characteristics are present in microemulsions, so that the loaded drugs can diffuse passively as well get significantly partitioned in the variable lipophilic-hydrophilic corneal barrier. This review will provide an insight into previous studies on microemulsions for ocular delivery of drugs using various nonionic surfactants, cosurfactants, and associated irritation potential on the ocular surface. The reported in vivo experiments have shown a delayed effect of drug incorporated in microemulsion and an increase in the corneal permeation of the drug.
"Microemulsion is a clear, thermodynamically stable, isotropic mixture of oil, water, surfactant and cosurfactant, which has typically a droplet diameter of approximately 100 nm or less (Hoar and Schulman, 1943; Danielsson and Lindman, 1981; Schulman et al., 1959). It has found widespread uses in pharmaceutics (Lawrence and Rees, 2000), food (Garti, 2003), and many other industries (Campbell and Rusling, 1999; Zarur and Ying, 2000; Lee et al., 2003; Wu et al., 1999). "
[Show abstract][Hide abstract] ABSTRACT: In this work, a hydrogel-thickened microemulsion (HTM) was investigated for delivering an extremely low concentration of drug molecule. The pseudo-ternary phase diagrams were constructed using isopropyl myristate (IPM), Tween 80, propylene glycol and water. The various HTM were prepared and characterized. We described that HTM has the combination of o/w microstructure of microemulsion and the three-dimensional gel network of hydrogel in continuous phase using transmission electron microscope. The stability tests showed that HTM had good stability. The influence of the addition of hydrogel into microemulsions on the viscosity and permeation ability is investigated. The abilities of HTM to deliver an extremely low concentration of triptolide as a model drug were evaluated using the in vitro permeation studies. The permeation rates of triptolide from various HTM were 2.2-3.6 times over that from the control hydrogel. The addition of 2% menthol into HTM consisting of 3% IPM, 30% Tween 80, 15% propylene glycol, 0.75% carbomer 940 resulted in the highest permeation rate of 0.105+/-0.006microcm(-2)h(-1), which was 5.8 times over control gel. The powerful permeation enhancing ability of HTM with a suitable viscosity makes it promising alternative carrier for transdermal administration of drug molecule at an extremely low concentration.
International Journal of Pharmaceutics 09/2007; 341(1-2):78-84. DOI:10.1016/j.ijpharm.2007.03.052 · 3.65 Impact Factor
"Microemulsions were first introduced by Hoar and Schulman in 1943 : they are isotropically clear, and thermodynamically stable dispersions of two immiscible liquids such as oil and water, stabilized by relatively large amount of surfactant and usually in conjugation with a cosurfactant, typically a short to medium chain alcohols . Microemulsions are clear fluids of low viscosity and may form a number of different structures, e.g., oil-in-water (o/w) or waterin-oil (w/o) droplets, and bicontinuous structures, over a wide range of compositions dependent on the properties of the oil and the surfactant. "
[Show abstract][Hide abstract] ABSTRACT: Attempts were to develop microemulsion systems using medium chain triglyceride, deionized water, and TPGS as surfactant for the oral delivery of protein drugs or poorly water-soluble drugs. Phase diagrams were constructed to elucidate the phase behavior of systems composed of Captex 300 and water with D-alpha-tocopheryl polyethylene glycol 1000 succinate (TPGS) as main surfactant, polysorbates (Tween 20, Tween 40, Tween 60 and Tween 80) as adjuvant surfactants, and polyethylene glycols (PEG 400 and PEG 600) and polyols (ethanediol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol and glycerin) as cosurfactants. The ratios of TPGS to Tweens, PEGs or polyols (K(m)) were set at 4/1, 2/1, 1/1, 1/2, and 1/4. The phase diagram for H(2)O/Captex 300/TPGS system reveals that when TPGS was used as a sole surfactant, it is not capable of producing isotropic solutions of water and oil over a wide range of the compositions. H(2)O/Captex 300/TPGS/Tweens systems with various K(m), regardless of the adjuvant surfactant used were capable of producing an isotropic phase. The extension of microemulsion phase and the presence and extension of the gel phase were found to be dependent on the surfactant mixture. The phase diagrams of H(2)O/Captex 300/TPGS systems using polyols as cosurfactants demonstrate that the types of polyols have a slight effect on the region of existence of the microemulsions. Comparison between the isotropic regions for the polyols system reveals that as the relative concentration of polyols increase, the isotropic region decrease in size. This decrease is towards the S(mix)-water axis indicating that as the relative concentration of polyols increases the maximum amount of oil solubilized decreases. The gel region decreased in size with the increase of polyols weight ratio. All polyols do not solubilized Captex 300 without using TPGS as surfactant.
Note: This list is based on the publications in our database and might not be exhaustive.
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.