Combination therapy with vitamin D analogues.

Monotherapy with vitamin D analogues has been shown to be effective in the treatment of psoriasis. Vitamin D analogues have also been used in combination with other topical therapies, systemic therapies and phototherapy. In many instances, the efficacy of these other treatments can be maximized and adverse effects minimized when combined with vitamin D analogues. The combination of a topical corticosteroid with a vitamin D analogue can work synergistically to improve efficacy and reduce the side-effects from both treatments. However, caution must be used when mixing the two agents, as some topical corticosteroids will result in the degradation of the vitamin D analogue. Benefit from phototherapy is also increased when using vitamin D analogues, so that greater improvement occurs with fewer treatments. Effects on minimal erythema dose must be considered and the potential for ultraviolet blocking by vitamin D analogues may affect treatment. Some vitamin D analogues may also be susceptible to degradation by certain wavelengths of ultraviolet light. Combining vitamin D analogues with systemic agents exerts a dose-sparing effect, thus reducing the possibility of side-effects, but such combinations require further study. As long as treatments are used correctly, the benefits of combination therapy with vitamin D analogues usually outweigh the few drawbacks.