The effect of a benzalkonium chloride-containing nasal spray on human respiratory mucosa in vitro as a function of concentration and time of action.

Human respiratory mucosa was exposed to oxymetazoline nasal spray in varying concentrations and for varying periods of time in vitro. The drug destroyed the tissue in a concentration- and time-dependent manner. In the experiments with various concentrations of the spray, some tissue fragments retained their viability throughout the experiment. This number increased parallel to a decrease in concentrations of the test substance. All the tissue fragments exposed to undiluted nose spray underwent severe destructive alterations during the exposure period. These alterations appeared first and were most extensive in those exposed for the longest periods of time. It has previously been demonstrated that the toxic effect of oxymetazoline nasal spray in vitro is probably due to the preservative benzalkonium chloride. The apparent lack of consistency between the toxic effects of benzalkonium chloride in vitro and in vivo is discussed, with special reference to protective systems absent in vitro but present in vivo.