Case study: cyproheptadine and aggression in a five-year-old boy

Cyproheptadine is an antihistamine and serotonin antagonist given to children for allergies, migraine headaches, and growth problems. A 5-year-old boy began to have episodes of violent behavior after the initiation of cyproheptadine therapy. After cyproheptadine was discontinued, the aggression ceased over the course of a few weeks. Although there are other causal explanations possible in this case, cyproheptadine seems the most likely cause of the violent behavior, especially in view of the literature on the relation between serotonin and aggression.