Microemulsion

Oral route has been considered as most convenient route but restricted to only hydrophilic compounds having GI stability and greater dissolution. The delivery of lipophilic compounds has been area of interest since most of the drugs under discovery shows limited bioavailability. Self-emulsifying delivery systems (SMEDDS) has drawn a greater attention in the formulation of poorly soluble compounds where increase in the absorption and permeation of the drug has observed. The self-emulsification which occurs in the case of SMEDDS has shown a potential advantage over conventional emulsion due to the fine globules formed upon dilution. The recent trends such as dry emulsion, s-SMEDDS, SNEDDS thoroughly investigated. This article, attempts to present the overview of the SMEDDS along with its formulation, application and characterization.

The objective of the present research was to develop and characterize an olive oil based oral microemulsion systems for famotidine, is a BCS class III drugs which are known to have high solubility but low permeability. An olive oil based microemulsion formulation with Tween-80 as surfactant, and PEG-400 as co-surfactant, was developed for oral delivery of famotidine. Pseudoternary phase diagram was constructed to determine the microemulsion existing zone. Optimized microemulsion was evaluated for its transparency, droplet size, polydispersity index, zeta potential, viscosity, conductivity, DSC studies, SANS studies. The results showed that maximum oil was incorporated in microemulsion system that was contained surfactant to co-surfactant ratio (Km) of 2:1. The optimized microemulsion formulation containing olive oil (7.14%), Tween-80 & PEG-400 [Smix=64.29% (2:1 ratio)], and distilled water (28.57%), had a droplet size (10 times diluted) and zeta potential (10 times diluted) of 170.1 nm and -6.58 mV respectively. Particle size characterization of the resulting microemulsion is essential in ensuring stability and efficient dosage. FTIR and DSC studies revealed the compatibility among the famotidine and microemulsion components. The experimental SANS data of optimized formulation fit well by spherical micelles interacting with hard sphere potential. These results demonstrate microemulsion formulation may be used as an effective and alternative drug delivery system for the antiulcer oral therapy with famotidine.

Rheumatoid arthritis is a common inflammatory disease characterized by progressive bone and cartilage destruction, A full cure for rheumatoid arthritis  is yet to be discovered but  Microemulsion containing NSAID can be used as best option for the management of pain in Rheumatoid arthritis 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.  Association of drugs with Microemulsion is normally noncovalent, based on collective strength of weak binding forces which are broken to release drug. The small droplets of Microemolsion provide better adherence to membranes and transport NSAID molecules in a controlled fashion for the pain management of Rheumatoid Arthritis. These adaptable delivery systems provide protection against oxidation, enzymatic hydrolysis and improve the solubilization of lipophilic drugs and hence enhance their bioavailability.

The novel carriers have been exploited through almost all the routes of administration. Many newer carriers are evolving with the advent of technology and the demand of targeted delivery like microemulsions. Microemulsions are clear, stable, isotropic mixtures of oil, water and surfactant. These systems are currently of interest because of their considerable potential to act as drug delivery vehicles by incorporating a wide range of drug molecules. In addition to oral and intravenous delivery, they are amenable for sustained and targeted delivery through nasal, pulmonary, vaginal and topical routes. The intent of the paper focuses on use of microemulsion technology in intranasal drug delivery along with mechanism.

  Microemulsions are clear, thermodynamically stable, isotropic mixtures of oil, water and surfactant, frequently in combination with a co-surfactant. They offer numerous advantages like improved solubilization of both hydrophilic and lipophilic drugs, better bioavailability, prolong and targeted release, enhanced permeation across biological membranes, protection against oxidation, better stability and ease of manufacturing as well as processing. These systems are currently of interest to the pharmaceutical scientist because of their unique characteristics and considerable potential to act as drug delivery carrier by incorporating a wide range of drug molecules. In order to appreciate the potential of microemulsions as delivery carrier, this review gives an overview of the microemulsion properties, formulation, phase behaviour, characterization and application of microemulsions as a drug delivery carrier.