Approximately one-third of newly discovered drug molecules show insufficient water solubility and therefore low oral bioavailability. Different lipid-based formulations have been explored in the past few decades to improve the oral delivery of such compounds. Self-nano-emulsifying drug-delivery systems (SNEDDSs) are one of the emerging strategies developed to tackle the issues associated with their oral delivery.

Self-Nano-emulsifying drug delivery systems (SNEDDS), which are isotropic mixtures of oils, surfactants, solvents, and co-solvents/surfactants, can be used for the design of formulations in order to improve the oral absorption of highly lipophilic drug compounds. The efficiency of oral absorption of the said drug from such type of formulation depends on many formulation-related parameters, such as surfactant concentration, oil/surfactant ratio, the polarity of the emulsion, droplet size, and charge, all of which in essence determine the self-emulsification ability. With the growing interest in this field, there is an increasing need for the selection of excipients guidelines to obtain an effective and safe delivery system with improved bioavailability. The aim of this review is to present the mechanism of self-emulsification, composition, the role of various excipients, formulation approaches, different techniques, evaluation parameters, factors affecting SNEDDS, advantages, drawbacks, applications, and future trends. This review also offers an updated overview of SNEDDS application from the biopharmaceutical point of view, various techniques used for the transformation of liquid SNEDDS into solid dosage forms, and regulatory status of SNEDDS. The present review gives an insight into SNEDDS for the oral administration of both lipophilic and hydrophilic compounds.