AbstractChinoin-170 (Ch-170; 3,7-dihydro-1,3-dimethyl-7-[(5-methyl-1,2,4-oxadiazol-3-yl)methyl]1H-purine-2,6-dione) is a new antitussive with bronchodilating activity. Its effects on the ciliary beating frequency (CBF) and mucociliary clearance were studied. In tracheal explants of rats, Ch-170 dose-dependently at concentrations 2 and 5 mg mL−1 depressed CBF by 24 and 33%, respectively. In human mucosal explants, however, no effects were seen at concentrations up to 5 mg mL−1. In anaesthetized guinea-pigs, an intravenous 50 mg kg−1 dose of Ch-170 caused no changes, and 100 mg kg−1 increased the CBF by 15%. Intravenous Ch-170 dose-dependently increased by 93 (50 mg kg−1), 179 (70 mg kg−1) and 253% (100 mg kg−1) the tracheobronchial mucociliary clearance in rabbits. The effect, studied using 99mTc-labelled red blood cells as a marker, was of similar quantity to that brought about by administering 16, 25 and 40 mg kg−1 doses of bromhexine. It is concluded that unlike many older antitussives, Ch-170 in-vitro only slightly decreases the CBF in rats and has no adverse effects on the CBF in human mucosal explants at concentrations up to 5 mg mL−1. In-vivo, Ch-170 does not significantly alter the CBF in guinea-pigs, but dose-dependently increases the mucociliary clearance in rabbits. The increase is most probably a result of changes in the production and the properties of respiratory mucus.
