- Treatment with any systemic medications which in the opinion of the investigator might counter or influence the trial aim (including anti psoriasis medications, eg, corticosteroids, cytostatics or retinoids) or medications which are known to provoke or aggravate psoriasis (eg, beta blocker, anti malarial drugs, lithium) or phototherapy/psoralen+UVA (PUVA) within 4 weeks preceding the treatment phase of the trial and during the trial.