CNS effects of the antihistamines diphenhydramine and terfenadine (RMI 9918).

The quantitative EEG profile of a putative antihistaminic drug, terfenadine, was determined in a crossover comparison with diphenhydramine in normal male volunteers. Terfenadine failed to elicit the characteristic EEG or behavioral effects of sedative antihistaminics, and was distinguishable from diphenhydramine. The EEG profile confirmed the lack of CNS effect observed in preclinical and clinical trials.