ABSTRACT

Every agent known to have an antipsoriatic effect has been used in combination with UV therapy and some have been fairly thoroughly evaluated. An important question to consider before using a combination therapy is: has the combination treatment been shown to be more effective than the primary treatment used alone? At first glance this question might sound silly and evoke a response of two agents must be better than one, but this is not necessarily true. Tar clearly is effective in psoriasis but, as discussed earlier, when combined with erythemogenic doses of UVB radiation no therapeutic effect of tar can be detected. Or put more simply, the weak therapeutic effect of tar is swamped by the more potent therapeutic activity of UVB radiation. Therefore, it is important to establish the therapeutic benefit of a second agent; otherwise the patient could be exposed to unnecessary potential adverse effects from that agent.