Pentoxyverine

While the mechanism of antitussive action of pentoxyverine is not fully understood, it is thought to be mediated via sigma-1 receptors expressed in the central nervous system. Pentoxyverine acts as an agonist at sigma receptors with the Ki of 75±28 nM, as demonstrated in a competitive binding assay. The function of sigma receptors on cough suppressant activities is unclear, however these receptors are highly expressed in the nucleus tractus solitarius (NTS) of the brainstem where the afferent fibres first synapse. NTS is located very close to the cough centre in the brainstem thus may function as a ‘gate' for the cough reflex and allow sigma-1 receptor agonists to modulate afferent activity prior to reaching the cough center. It is suggested that highly lipophilic sigma-1 agonists may penetrate the CNS following systemic administration. When administered as aerosols, sigma-1 receptor agonists may temporarily act in the periphery to modulate cough by acting activate sigma receptors expressed in the lungs. However there is limited evidence of peripheral localization of the sigma agonists following aerosol administration and the ruling out of systemic exposure. The local anesthesia action of pentoxyverine may occur through inhibition of voltage-gated Na(+) currents.