In order to test the advantage of vitamin D₃ preparations in liposomal form, calcitriol, the natural activated form of vitamin D₃, and tacalcitol, a vitamin D₃ analogue, were employed in various concentrations and using different vehicles in the mouse tail test, an animal model for testing the antiparakeratotic efficacy of topical medications. The optimal concentration in petrolatum turned out to be similar to that in commercial preparations. The liposomal preparations were superior to those in petrolatum and to those in nonliposomal phospholipids. The antiparakeratotic potency (drug activity) of liposomal tacalcitol in a concentration of 2 µg/g was twice that of the commercial preparation with a higher concentration of 4 µg/g. These results suggest that the use of liposomal vitamin D₃ preparations can achieve a given antipsoriatic effect with a reduced concentration of the active substance thereby reducing the risk of skin irritation and of hypercalcemia.

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