Why is the vehicle important when recommending a topical corticosteroid?

The choice of vehicle may affect several factors that relate to potency, including bioavailability, lipid solubility, and the partition coefficient of each product. A vehicle should also be selected based on indication, disease severity and extent, body region to be treated, as well as patient preference. A steroid molecule in an ointment base will result in the most potent preparation, because it is the most occlusive with the greatest penetration. This is followed by creams, lotions, solutions, gels, and sprays. Compounding, dilution, or addition of ingredients to a proprietary product should be discouraged. This practice can affect the uniformity, stability, and/or bioavailability of the active ingredient. Also, the cost is greater because additional labor is required.