Self Emulsifying Drug Delivery Systems as a formulation strategy to improve oral bioavailability
by Jurgen Vercruysse, PhD, Project Leader, Eurofins Amatsigroup (CDMO)
The majority of new chemical entities show limited aqueous solubility. The oral delivery of these compounds presents a major challenge due to low bioavailability. Several formulation strategies are applied to improve the solubility, including salt formation, particle size reduction, solid dispersions and complexation. Especially when lymphatic absorption is targeted, lipid-based formulations like Self Emulsifying Drug Delivery Systems (SEDDS) are more appropriate.
SEDDS are isotropic mixtures of drugs, lipids, and surfactants, potentially with one or more hydrophilic co-solvents or co-emulsifiers. Following their oral intake, the digestive motility of the stomach and intestine provide the agitation necessary for self-emulsification into a fine oil-in-water emulsion. A distinction is made between SEDDS and self micro-emulsifying drug delivery systems (SMEDDS) or self nano-emulsifying drug delivery systems (SNEDDS), on the basis that the latter have a smaller droplet size and are visibly transparent instead of opalescent. SEDDS present the drug in a dissolved form, avoiding the rate-limiting dissolution step, and the small droplet size provides a large interfacial area for drug absorption. Surfactants help to solubilise the lipophilic drug compound and avoid precipitation of the drug in the gastrointestinal lumen. SEDDS are applied either for indications where a quick onset of action is required or for sustained delivery by the addition of polymers.
Eurofins Amatsigroup (CDMO) offers the design and formulation of SEDDS based on pre-formulation solubility and phase-diagram studies to identify the most efficient self-emulsifying region. Ultimately, SEDDS are formulated as an oral solution in vials or gelatin capsules or are transformed into granules, pellets, or powders for filling in hard capsules or for tablet production. Liquid SEDDS can be converted into solid SEDDS by adsorption on solid carriers using conventional technologies like spray drying, granulation, and melt extrusion. To conclude, SEDDS are a unique and industrially feasible approach to overcome the problem of low oral bioavailability associated with lipophilic drugs.
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