Histamine synthesis in man: inhibition by 4-bromo-3-hydroxybenzyloxyamine.

Oral administration of 4-bromo-3-hydroxybenzyloxyamine to normal humans resulted in decreased urinary excretion of histamine; the normal increase in urinary levels of histamine after oral histidine loading was prevented. In two patients having systemic mastocytosis, additional evidence of inhibition of biosynthesis of histamine included marked reduction in symptoms attributed to histamine, and prevention of symptomatic exacerbation associated with histidine loading.