Abstract

Microemulsions are being increasingly used as vehicles for lipophilic drugs. They can be used for parenteral drug delivery systems (Date and Nagarsenker 2010) or could be encapsulated into softgel capsules as a convenient solid dosage form (Gullapalli 2010). In contrast to conventional emulsions, microemulsions are small droplet size (typically between 20 and 200 nm) (Talegaonkar et al. 2008) and exhibit long-term stability (McClements 2012). They have been proven to promote the gastric-intestinal (GI) absorption of lipophilic drugs and consequently enhance the bioavailability of some active pharmaceutical ingredients (API) (Lawrence and Rees 2000). Food and Drug Administration in the United States (U.S. FDA) has classified APIs into four groups based on the Biopharmaceutical Classification System (BCS). APIs in class II (high permeability, low solubility) and class IV (low permeability, low solubility) are ideal candidates for microemulsion-based drug delivery systems due to their poor solubility in the aqueous phase. Table 10.1 gives examples of drugs that have been successfully delivered in microemulsion form.