Intranasally and orally administered antihistamine treatment of experimental rhinovirus colds.

Although antihistamines are widely used for symptomatic treatment of seasonal (allergic) rhinitis, the role of histamines in the pathogenesis of infectious rhinitis is not clear. Two antihistamines, orally administered chlorpheniramine maleate (CM) and diphenhydramine hydrochloride (DH) administered by intranasal spray, were used under double-blinded, randomized, placebo-controlled conditions to assess both tolerance and efficacy in volunteers with experimental rhinovirus (RV) colds. In the initial trial, CM (4.0 mg per treatment) was ingested 4 times daily for 4 days beginning 24 h after intranasal inoculation of RV type 29 in susceptible volunteers. In the second trial, DH was sprayed intranasally 4 times daily (2 mg per treatment) for 5 days beginning 24 h after inoculation of RV type 39. Clinical colds occurred in 60% of the CM group (n = 13) and 73% of the placebo (n = 15) in the first study, and in 66% of the DH group (n = 12) compared with 81% in the placebo group (n = 11) in the second. Both CM and DH were well tolerated but had no significant effects on nasal symptoms or nasal mucus production. The findings provide additional evidence against an important role for histamine in the pathogenesis of nasal symptomatology in rhinovirus colds.