Nasal Resistance Observations in Decongestant Spray Trials

Abstract

Forty-two patients with common colds entered a randomized, double-blind crossover trial of topical nasal therapy. Four sprays (phenylephrine/thenyldi-amine/benzalkonium, phenylephrine/benzalkonium, thenyldiamine/benzalko-nium, and placebo) were instilled in the right nostril. Nasal flow resistance (R_n) was measured in the treated right nostril (R_nr) and the untreated left passage (R_nl) at baseline, and over 6 hours, by electronic posterior rhinometry; an efficacy ratio was calculated for each spray. Nasal resistance rose in the untreated left nostril and the placebo-treated right nostril; the active sprays induced a drop in R_nr. Analysis of R_nr and covariant analysis of R_nr and R_nl indicated that the changes following the active solutions were statistically more significant than those following placebo, or occurring in the left nostril (p = 0.01 or better). The efficacy ratios for the active sprays did not differ from one another at the 95 per cent confidence interval. Estimates of R_n are sensitive indices of effective nasal therapy. Trials of topical medications allow two control references–a direct placebo observation in a treated nostril, and similar measurements in an untreated nostril (“no-placebo” placebo)–and enhance reliability.