Phospholipids are amphiphilic, endogenous molecules with excellent biocompatibility and tolerability. Therefore, they are an ideal choice for various “over-the-counter” (OTC) products, including formulations for sensitive tissue such as the ocular surface. Phospholipids can serve as active principle, as excipients to modulate tissue interaction, and as building blocks to form lipid particles such as emulsions and liposomes (Fig. 1).

Application in topical OTC products

Phospholipids are essential components of all mucosal surfaces. On the ocular surface, phospholipids stabilize the outer non-polar lipid layer that prevents evaporation and thereby keeps the eye mucosa moisturized. In the nasal and oral cavity, a surfactant film covers the air-mucus interface, which contains mainly saturated and unsaturated phospholipids (Fig. 2). Topical phospholipid-based products restore and moisturize mucosal surfaces in a natural way. For this purpose, phospholipids often serve as active principle but may also be combined with additional actives.

Further applications

Also, in a broad variety of other OTC formulations phospholipids are used. In dermal topicals, phospholipids can modulate intrinsic metabolism pathways, restore the skin barrier properties, or enhance skin interaction of co-formulated actives. In oral dosage forms, phospholipids function as emulsifiers and building blocks for colloidal species or serve as an active, typically in products for liver protection.

In addition, phospholipids are used as technical excipients, e.g., in suppositories. The highly versatile use as technical and functional components underscores the suitability of phospholipids for a wide variety of OTC formulations.