Physiologic/clinical comparisons of a sustained-release decongestant combination, its components and placebo in patients with allergic rhinitis.

Fifteen subjects with chronic allergic rhinitis had measurements of nasal airways flow/resistance (Rn) made before, and for 12 hours after, single doses of a sustained release decongestant combination, some of its components given alone or together, and placebo, in a randomized double-blind trial. The magnitude of improvement in Rn was statistically greater for the the four active preparations than for placebo over the first 8 hours; the effects of phenylpropanolamine/chlorpheniramine were still present after 10 hours, while at the end of 12 hours only the full triple-drug capsule had significant activity. Patient-estimates of symptomatic improvement generally mirrored these physiologic changes although statistical differences among the active capsules were not delineated. The data confirm the ability of electronic posterior rhinometry to discriminate between the effects of active medications and placebo at the 95 per cent confidence level or better and suggest that observed decreases in elevated Rn mean reflected helpful clinical activity as well as increased nasal patency.