Gastro-retentive drug delivery system (GRDDS) has gained immense popularity in the field of oral drug delivery recently. It is a widely employed approach to retain the dosage form in the stomach for an extended period of time and release the drug slowly that can address many challenges associated with conventional oral delivery, including poor bioavailability. Different innovative approaches like magnetic field assisted gastro-retention, plug type swelling system, muco-adhesion technique, floating system with or without effervescence are being applied to fabricate GRDDS. Apart from in vitro characterization, successful GRDDS development demands well designed in vivo study to establish enhanced gastro-retention and prolonged drug release. Gama scintigraphy and MRI are popular techniques to evaluate in vivo gastric residence time. However, checking of their overall in-vivo efficacy still remains a major challenge for this kind of dosage form, especially in small animals like mice or rat. Reported in vivo studies with beagle dogs, rabbits, and human subjects are only a handful in spite of a large number of encouraging in vitro results. In spite of the many advantages, high subject variations in gastrointestinal physiological condition, effect of food, and variable rate of gastric emptying time are the challenges that limit the number of available GRDDS in the market. This review article highlights the in vivo works of GRDDS carried out in the recent past, including their limitations and challenges that need to be overcome in the near future

Self-emulsifying drug delivery system (SEDDS) is an isotropic mixture of lipid, surfactant and co-surfactant, which forms a fine emulsion when comes in contact of an aqueous medium with mild agitation. SEDDS is considered as a potential platform for oral delivery of hydrophobic drug in order to overcome their poor and irregular bioavailability challenges. In spite of fewer advantages like improved solubility of drug, bypassing lymphatic transport etc., SEDDS faces different controversial issues such as the use of appropriate terminology (self-microemulsifying drug delivery system; SMEDDS or self-nanoemulsifying drug delivery system; SNEDDS), presence of high amount of surfactant, correlation of in vitro model to in vivo studies, lack of human volunteer study and effect of conversion of SEDDS to final administrable dosage form on pharmacokinetic behavior of the drug. In this review, potential issues or questions on SEDDS are identified and summarized from the pharmacokinetic point of view. Primarily this review includes the conflict between the influences of droplet size, variation in correlation between in vitro lipolysis or ex-vivo intestinal permeation and pharmacokinetic parameters, variation in in vivo results of solid and liquid SEDDS, and potential challenges or limitation of pharmacokinetic studies on human volunteers with orally administered SEDDS. In the past decades, hundreds of in vivo studies on SEDDS have been published. In the present study, only the relevant article on in vivo pharmacokinetic studies with orally administered SEDDS published in past 5-6 years are analyzed for an up to date compilation.

Background: Most of the active pharmaceutical ingredients discovered recently in pharmaceutical field exhibits poor aqueous solubility that pose major problem in their oral administration. The oral administration of these drugs gets further complicated due to their short bioavailability, inconsistent absorption and inter/intra subject variability. Methods: Pharmaceutical emulsion holds a significant place as a primary choice of oral drug delivery system for lipophilic drugs used in pediatric and geriatric patients. Pharmacokinetic studies on nanoemulsion mediated drugs delivery approach indicates practical feasibility in regards to their clinical translation and commercialization. Results: This review article is to provide an updated understanding on pharmacokinetic and pharmacodynamic features of nanoemulsion delivered via oral, intravenous, topical and nasal route. Conclusion: The article is of huge interest to formulation scientists working on range of lipophilic drug molecules intended to be administered through oral, intravenous, topical and nasal routes for vivid medical benefits.