[Ambroxol and protective reflexes of the respiratory tract]

Ambroxol, trans-4-/(2-amino-3,5-dibromobenzyl) amino/cyclohexanol hydrochloride, a drug used to increase surfactant secretion in the lungs, has been reported to be effective in reducing exacerbation of chronic bronchitis and in the protection from inflammatory reactions (Bianchi et al., 1990). The effect of this drug on the defence reflexes of airways remains unknown.

The aim of this study was to follow the changes in the cough reflex after administration of ambroxol in the dose of 10 mg/kg body weight. Ambroxol was administered i.p. and perorally. Further, we investigated the bronchodilatory activity of ambroxol.

In the present study, the effects of ambroxol on the cough reflex in the cats were investigated. The drug was administered intraperitoneally and perorally in the dose of 10 mg/kg body weight. Cough was induced by mechanical stimulation of airways. The effect of ambroxol on the smooth muscles of guinea pig (weight 300-400 g) airways was investigated in vitro. The contractions were induced by carbachol in the concentration of 10(-5) mol/l and by histamine in the same concentration.

The results indicate that ambroxol, when administered intraperitoneally attained a total fall in cough parameters by about 51.6%. Ambroxol, when administered perorally suppressed all cough parameters by about 37.04%. Further, ambroxol has no effect on carbachol-induced contraction of smooth muscles of airways. The histamine-induced contraction of tracheal smooth muscles was significantly reduced after administration of ambroxol in the concentration of 10(-4) mol/l. The lung smooth muscles of guinea pig became relaxed after administration of the drug in the concentrations of 10(-5)-10(-4) mol/l.

The study suggests, that ambroxol has a cough-suppressive effect. More expressive effect of the drug on smooth muscles of airways was found out in case of histamine-induced contraction. (Fig. 6, Ref. 13.)