In vitro pharmacology of ambroxol: Potential serotonergic sites of action.

Aims: Ambroxol is a muco-active agent with multiple, clinically relevant effects in the airway. Despite its widespread use and well documented clinical efficacy, there are few data on its mechanism of action and receptor pharmacology beyond sodium channel blockade and inhibition of guanylate cyclase. Accordingly, in vitro studies were conducted to determine its overall receptor pharmacology and possible sites of action.

Materials And Methods: In vitro radioligand binding/enzyme inhibition studies were conducted at 62 receptors, ion channels and enzymes using standard techniques. Additional in vitro studies were conducted to establish the potency of ambroxol at selected sites.

Key Findings: These studies indicate that ambroxol has affinity for the 5-HT serotonin receptor, as well as affinity for the 5-HT serotonin transporter (SERT), with IC values of 17,600 nM and 19,500 nM respectively. In vitro functional studies in isolated guinea pig colon indicate that ambroxol is a 5-HT serotonin receptor antagonist with an IC value of 36,000 nM.

Significance: Together, these studies indicate that ambroxol may exert its beneficial properties via antagonism of the 5-HT serotonin receptor and/or inhibition of serotonin uptake (5-HT transport: SERT), in addition to its reported effects at the sodium channel and guanylate cyclase.