Double-blind, controlled study of clemastine fumarate, chlorpheniramine and placebo in the symptomatic treatment of seasonal allergic rhinitis in desensitized and nondesensitized patients.

: In double-blind trials clemastine fumarate 2.68 mg. chlorpheniramine 4 mg and placebo were randomly assigned to two groups of patients with seasonal allergic rhinitis. Thirty-nine desensitized patients were given one of the three test drugs in a parallel design; 67 nondesensitized patients each received two of the three drugs in a crossover design. Assessment of drug activity in each study was by whole body plethysmography and intranasal color photography as well as by subjective methods. Objective measurements showed clemastine fumarate was significantly superior to placebo and often better than chlorpheniramine in decreasing true nasal resistance and relieving nasal congestion. High placebo responses characterized the subjective evaluations, although the active drugs were clearly better. Responses varied somewhat between desensitized and nondesensitized patients. The number of reports of sedative effect, high in all groups, seemed to be more closely related to these antihistamine conditioned patients than to activity of the drugs themselves, based on previous reports of low sedation with clemastine fumarate. The techniques described proved very useful in distinguishing relative activity of antihistamines. Clemastine fumarate, the new antihistamine studied, appears to offer certain advantages over the older drug, chlorpheniramine.