IJPI’s Journal of Pharmaceutics and Cosmetology

IJPI’s Journal of Pharmaceutics and Cosmetology

INTRODUCTION
Drug formulation plays a very vital role for its delivery to the site of action. Variations in formulation of any
drug can affect bioavailability. The Drugs can show different degree of availability from one type of dosage form to
another when given by the same route. The biological availability of a drug is greatly affected by its physical state and
formulation of the dosage form and hence the therapeutic activity of a drug product.
The difference in product formulation can lead to large difference in speed of onset, intensity and duration of
drug response. The study of formulation factors in pharmacological response can be known as the science of biological
availability of particular preparation (Badawy et al., 2006).
Oral route is a preferred rout owing to convenience in application and having a good bioavailability. Solution
form is convenient in both elderly and young patient groups. One of commonly prescribed drugs are cough or cold
medicines, frequently available in solution forms. In oral preparations, solution dosage form is considered to have a
rapid and complete absorption in most of cases. For any oral dosage form, state of stomach and rate of stomach
emptying plays key role in drug absorption. Potent lipophilic drugs having poor water solubility show a poor oral
bioavailability (Kommuru et al., 2001). For these drugs as defined by Amidon et al., 1995 ―low solubility/high
permeability class‖ rate-limiting step in their absorption is dissolution in the lumen. Studies have been conducted to
increase oral bioavailability of lipophilic drugs or otherwise they will not have much clinical efficacy. Such drugs
when prepared in suspension form of finely divided powder show a better bioavailability. Most popular approach used
for these drugs is to incorporate these active lipophilic components into inert lipid vehicles (Aungst, 1993).Such poor
water soluble drugs can be prepared by dissolving them in either water/alcohol or glycerol solvents, oils ( Burcham et
al., 1997) and surfactant dispersions (Serajuddin et al., ;1988 Aungst et al., 1994). Use of self-emulsifying agents has
been suggested in many studies (Wakerly et al., 1986; Charman et al., 1992; Craig et al., 1993; Shah et al., 1994).
Other studies suggest emulsions can be used in this regard (Stella et al., 1978; Palin et al., 1986; Toguchi et al., 1990;
Myers and Stella 1992; Kararli et al., 1992). Liposomes can also be used to dissolve poorly water soluble drugs
(Schwendener and Schott 1996) . All these formulations enhance absorption with advantages and limitations with each
formulation. Compounds with hard crystal structure and non ionic drugs with higher melting points can be prepared
with such types of formulations. It is reported that ―self-emulsifying drug delivery systems‖(SEDDS) are
homogeneous mixtures of natural or synthetic oils, solid or liquid surfactants, or alternatively, one or more hydrophilic
solvents and co-solvents (Constantinides, 1995). The most important quality of these systems is their ability to form
oil-in-water (o/w) emulsions or microemulsions on gentle agitation when followed with aqueous dilution by aqueous
phases. This property causes SEDDS to increase the oral bioavailability of poor water soluble drugs and make them
sufficiently soluble in oils or oil/surfactant formulations (Tatyana and Simon 2000).