Selfmicroemulsifying

Self-microemulsifying drug delivery systems, often abbreviated as SMEDDS, are a type of liquid dosage formulation designed to improve the oral bioavailability of poorly soluble drugs. These systems consist of a mixture of oils, surfactants, and co-surfactants, along with the drug. Upon contact with aqueous media, such as gastrointestinal fluids, the SMEDDS spontaneously disperses to form a fine emulsion of oil droplets, typically ranging from 1 to 100 nanometers in diameter. This fine dispersion significantly increases the surface area of the drug, promoting its dissolution and absorption.

The spontaneous formation of the microemulsion is driven by the thermodynamic stability of the system, which is achieved by carefully selecting the components. The surfactant lowers the interfacial tension between the oil and water phases, while the co-surfactant helps to stabilize the resulting small droplets and prevent coalescence. The drug is dissolved within the oil phase or incorporated into the surfactant/co-surfactant mixture.

SMEDDS offer several advantages, including enhanced drug solubility, improved oral bioavailability, simplified manufacturing processes, and the potential for developing liquid formulations that can be encapsulated into soft or hard gelatin capsules. They are particularly beneficial for lipophilic drugs belonging to BCS class II and IV. The effectiveness of a SMEDDS formulation is evaluated based on its drug encapsulation efficiency, droplet size distribution after emulsification, and in vitro drug release profiles, which are often correlated with in vivo pharmacokinetic performance.