The cutaneous bioavailability of a topically applied drug depends on the galenic concept of the formulation

In addition to the physicochemical properties of the drug, its penetration is mainly dependent on its concentration gradient (Fick's diffusion law)

Immediately after application of the topical preparation, its vehicle undergoes metamorphosis, which causes molecular rearrangement of the vehicle components

To achieve the highest possible concentration gradient of a drug after application, the concept of supersaturation can be applied

In supersaturation, a stable solution is achieved by the selection of suitable solvents and pressure increase in the packaging material, which causes a supersaturated solution after application by evaporation of solvent fractions

This leads to supersaturation without precipitation in a circumscribed concentration range (Ostwald-Miers range)

The resulting high concentration gradient can be used for improved cutaneous bioavailability of the drug