Chronic skin diseases such as Psoriasis show remissions and exacerbations. These remissions and exacerbations are interpreted as resulting from intercurrent events: psychological stress, focal infections and medications. In this volume of the Journal of Dermatological Treatment two cases have been described showing exacerbation of pustular psoriasis to fluoxetine. This report suggests that in addition to antimalaria drugs, betha-blockers, non-steroidal corticosteroids also fluoxetine may be a trigger for psoriasis.
The establishment of a causal relationship between a drug and disease aggravation is not simple as by definition it is an equation with two unknowns: the drug and the reason why the drug had been given. For example ones tetracyclins have been suggested to induce psoriasis; the infection – requiring this treatment – obviously is the permissive factor. Therefore, the temporarily relationship between initiation and discontinuation with appearance and disappearance of the skin diseases in itself is not sufficient to establish the relationship.
Some prudence is reasonable before concluding on a causal relationship with aggravation of psoriasis and other skin diseases. In fact rechallenge with the suspected drug in a phase that there is no disease requiring that medication is a prerequisite before establishing such relationship.