BACKGROUND: Intranasal oxymetazoline (OMZ) is used as a decongestant during common colds. Recently, intracellular adhesion molecule (ICAM) 1 receptor expression in vitro has been shown to be diminished by OMZ. ICAM-1 is the major receptor used by rhinovirus to gain entry to human cells. The objective of this study was to assess the effect of OMZ on geometric mean titer of rhinovirus in nasal lavage fluid after rhinovirus inoculation. METHODS: Volunteers with antibody titers of </=1:4 to rhinovirus type 39 were enrolled in a randomized, reference-controlled, double-blind study. Beginning 3 hours after intranasal challenge with 100-300 tissue culture infectious dose (TCID)(5)(0) of virus, subjects received active 0.05% OMZ (45 muL containing 22.5 mug of OMZ hydrochloride in citrate buffer) or reference control (physiological saline solution [PSS]) three times daily for 5 days. Rhinovirus was detected in fibroblast cultures. RESULTS: Geometric mean viral titer (log(1)(0)) in 34 rhinovirus-infected subjects receiving OMZ was 1.49 on day 2 compared with 2.24 in the 38 infected subjects receiving PSS (p = 0.04). On day 3, the mean titers were 1.45 and 2.08, respectively. Median length of viral shedding was 3.3 days (OMZ) and 3.4 (PSS). Duration of clinical illness was 6.1 days in both groups. CONCLUSION: Topical OMZ decreased viral titer on day 2 during experimental rhinovirus infection in normal volunteers.