Introduction: Oral delivery of more than over
one-half of the drug compounds through gastrointestinal
(GI) tract gets thwarted owing to their high
lipophilicity and consequently, poor aqueous solubility.
Oral bioavailability of such drugs, being primarily a
function of their solubility and dissolution, tends to
exhibit inadequate magnitude with high intra- and
inter-subject variability. Besides, oral bioavailability
also depends upon a multitude of other drug factors such
as stability in GI fluids, intestinal permeability,
resistance to metabolism by cytochrome P450 family of
enzymes present in gut enterocytes and liver hepatocytes,
and interaction with efflux transporter systems like
P-glycoprotein (P-gp). Figure 1 explicitly illustrates
the mechanisms of the physiological pathways through
which the bioavailability of a drug from the
conventional formulations tends to get impeded.
Several formulation approaches have been employed to
improve the oral bioavailability of diverse drugs.
Amongst these, oral lipid-based DDS have proved their
immense potential in improving the poor and inconsistent
drug absorption of many poorly water-soluble drugs,
especially following their administration after meals.
Self-emulsifying drug delivery systems (SEDDS) are
relatively newer lipid-based technological innovations
with immense promise in oral bioavailability enhancement
of drugs. These formulations have shown to reduce the
slow and incomplete dissolution of a drug, facilitate
the formation of its solubilized phase, increase the
extent of its transportation via intestinal lymphatic
system, and bypass the P-gp efflux, thereby augmenting
drug absorption from the GI tract. Figure 2 specifically
illustrates the lymphatic pathways thorugh which these
self-emulsifying formulations are known to carry the
drug from the GI mucosa to systemic circulation.