Methods of studying antihistamines.

A variety of ingenious methods have been devised to challenge and incite episodes of acute allergic rhinitis in susceptible individuals. These methods teach us much about basic mechanisms involved in the disease. There is some danger in using them for efficacy trials because antihistamines are only partially effective treatment for hay fever and the challenge administered could easily overcome the degree of protection. Additional studies may lead to a better understanding of the factors involved in challenges and hence, their usefulness in clinical testing. The out-patient trial design is successful in demonstrating efficacy in 40 to 60 per cent of trials. The field trial is 70 to 90 percent accurate in its findings. The clinical design of antihistamine trials has improved remarkably in the past 10 years. Because of the nature of the disadvantages discussed throughout this report, I would doubt that further improvements in design will occur in future years unless a substitute is found for subjective evaluations.