The aim of this study was to functionally evaluate the decongestant effect of a topical intranasal drug (Rhinofluimucil consisting of tuaminoheptane sulphate (CAS 6411-75-2, THS), a vasoconstrictor, combined with N-acetyl-cysteine (CAS 616-91-1, NAC). This was a double-blind randomized study, versus both xylometazoline and placebo. 18 subjects (8M and 10F, aged 20-47 years), unaffected by any rhinitic pathology, underwent anterior rhinomanometry. Following the basal evaluation (T0), subjects were randomly divided into three groups and subjected, in a double-blind manner, to nasal instillations (2 puffs per nostril) of THS/NAC (R), xylometazoline (O) and saline solution (P), respectively. Rhinomanometry was repeated after 5, 10 and 20 min (T5, T10, T20). Resistance and flow were measured in both nostrils at a pressure gradient of 150 Pa. After R and O nasal resistance significantly decreased from 0.30 Pa to 0.19 Pa and from 0.31 Pa to 0.17 Pa, respectively, and flow significantly increased; no effects were observed with placebo. In this study, THS/NAC showed rapid decongestant properties, with a significant decrease of resistance and increase of inspiratory flow. The same finding was observed with xylometazoline, but not with the placebo. The decongestant effect was rapid: it could already be observed at T5, and remained constant up to T20 without any rebound effect.