Functions of Lipids for Enhancement of Oral Bioavailability of Poorly Water-Soluble Drugs 719 improved drug absorption provided by self-emulsifying formulations, however, depends on the maintenance of the drug in the solubilised state before it can be absorbed from the GI-tract. Marketed Lipid-Based Dosage Forms Lipids are versatile tools for drug administration because they cover a wide array of different types of formulations, such as solutions, suspensions, emulsions, self-emulsifying systems, lipid particles, and microemulsions. The commercially available oral lipid-dosage forms are either filled in capsules or represent bulk oral solutions. Both soft and hard gelatine capsules are used for lipid-based formulations. Usually, liquid formulations are manufactured either as soft or hard gelatine capsules, whereas semisolid or solid formulations are filled into hard gelatine capsules. Parenteral formulations include emulsions, microemulsions, liposomes, lipid complexes, suspensions, and colloidal dispersions. The different kinds of formulations are generally divided into following categories: • • • • • • • • One-lipid excipient formulations Two-lipid excipients formulations Three-lipid excipients formulations Four-lipid excipients formulations Extended release formulations Microemulsions Oral suspensions s Oral solutions One-lipid excipients formulations The simplest lipid-based formulations contain only one excipient such as oleic acid, α- tocopherol, corn oil, peanut oil, sesame oil, medium chain triglycerides, or medium chain mono- and diglycerides. All such oral formulations are marketed in soft gelatin capsules. Many of the over-the-counter sold products contain polyethylene glycol or medium chain triglycerides as the solubilizing excipients (see Table 6). Tab. 6. Marketed one-lipid excipient formulations Marketed formulation Heminevrin® Marinol® Epadel® API Dosage form Manufacturer Clomethiazole Capsule (soft gelatin) Dronabinol Capsule (soft gelatin) Ethyl icosapentate Capsule (soft gelatin) AstraZeneka Solvay Pharmaceuticals Mochida Pharmaceuticals Country of sale UK USA Japan Sci Pharm. 2011; 79: 705–727