Spontaneous reporting of suspected adverse reactions to antihistamines: a national and international perspective

Twenty-one sedative and five non-sedating antihistamines are presently avai lable on the UK market. Analysis of spontaneous reports of suspected advers e drug reactions was performed for those drugs with more than 90 reported r eactions on the UK ADROIT database to the period ending 31 December 1997. T hus nine antihistamines, (four sedative antihistamines and five non-sedatin g antihistamines) were included. For each of the four sedative agents (azat idine, chlorpheniramine, diphenhydramine and trimeprazine), reactions assoc iated with the cardiovascular, gastrointestinal, central nervous systems, t he skin, general and psychiatric reactions made up more than 70% of total r eported reactions. For all four agents, fatal reactions constituted less th an 2.5% of total reactions. For each of the five non-sedating agents (acriv astine, astemizole, cetirizine, loratidine and terfenadine), reactions asso ciated with the cardiovascular, gastrointestinal central nervous systems, t he skin, general and psychiatric disorders together made up more than 75% o f total reported reactions. For all five non-sedating agents, fatal reactio ns constituted less than 1% of total reactions. However, there were 21 repo rts of fatality in association with terfenadine, 11 (52%) of which were eit her sudden deaths or those associated with a cardiac rate of rhythm reactio n. Analysis of the WHO database for non-sedating drugs showed a similar pat tern, with terfenadine being associated with the highest frequency of repor ts of potentially serious arrhythmias and of sudden death and death related to disturbances of cardiac rate and rhythm combined. Despite the limitatio ns of spontaneous reporting systems, comparison of the benefit-risk profile s of drugs using this data within a class of drugs can provide valuable inf ormation, and pharmacovigilance of antihistamines land all other agents) us ing this and other means should continue for the lifetime of their use in h umans.