EFFECTS OF SOME PRESERVATIVE AGENTS ON RAT AND GUINEA-PIG TRACHEAL AND HUMAN NASAL CILIARY BEAT FREQUENCY

Many preservatives commonly included in nasal drops and sprays are kno wn to impair mucociliary clearance. We studied the effects of four fre quently used preservatives on ciliary beat frequency (CBF) in respirat ory tissue. Sodium metabisulfite and chlorbutol did not change the CBF at concentrations up to 50 mg/L in rat tracheal mucosa. Chlorocresol 25 mg/L and 50 mg/mL reversibly decreased CBF (by 33% and 68%, respect ively) in 60 minutes. Benzalkonium chloride impaired CBF irreversibly already at a relatively low concentration (12.5 mg/L). To further clar ify these results, we studied the effects of the most ciliotoxic (benz alkonium chloride) and nonciliotoxic (chlorbutol) preservative on guin ea pig tracheal epithelium and human nasal mucosa. Although chlorbutol had no effect on the CBF, a dose-dependent decrease on CBF was seen i n guinea pig and human ciliated epithelium during their immersion in b enzalkonium chloride. At a concentration of 50 mg/L it stopped the cil iary activity in 40 minutes in guinea pig trachea, and in human nasal mucosa, benzalkonium chloride concentrations of 25 and 50 mg/L, decrea sed the CBF irreversibly (by 28% and 60%, respectively) in 60 minutes. These results suggest that chlorbutol is a safe and well tolerated pr eservative. Banzalkonium chloride is ciliostatic in vitro to rat, guin ea pig, and human respiratory mucosa. Therefore, prolonged clinical us e of benzalkonium chloride may impair mucociliary clearance, a major d efense respiratory mechanism.