The effects of vadocaine, dextromethorphan, diphenhydramine and hydroxyzine on the ciliary beat frequency in rats in vitro.

Mucociliary function is a major cleansing mechanism of the respiratory tract. Many drugs used in the treatment of respiratory diseases impair the ciliary beat frequency (CBF) of mucous membrane. Our aim was to study by means of a photoelectric technique, the effects of two antitussives--dextromethorphan and vadocaine--and two antihistamines--hydroxyzine and diphenhydramine--on the rat tracheal CBF in vitro. The CBF was measured from tracheal explants immersed in drug solutions. Dextromethorphan (1.0 mg/ml and 10.0 mg/ml) caused 16.9-20.8% decrease in the CBF during the 40 min. measurement period. Vadocaine (0.1 mg/ml and 0.5 mg/ml) decreased the CBF by 6.9%. Higher vadocaine concentrations caused a dose-dependent inhibitory effect so that mucociliary function stopped totally within 20 min. with 5.0 mg/ml vadocaine solution. Both diphenhydramine and hydroxyzine totally stopped the ciliary activity during 20 min. with concentrations of 2.5 mg/ml and 1.0 mg/ml. respectively. Locke-Ringer solution used as a control did not cause any change in the CBF. These results suggest that the antihistamines diphenhydramine and hydroxyzine are more ciliostatic than the antitussives dextromethorphan and vadocaine on the rat tracheal cilia in vitro. The results suggest further in vivo studies. The used photoelectric detection method proved to be suitable for evaluating drug effects on the CBF of respiratory mucosa.