Effect of a novel inhaled lidocaine powder formulation on cough threshold to nebulised distilled water in humans

<bold>Background:</bold> Local anaesthetics have been reported to have antitussive effects due to their ability to block NaV+ channels in sensory nerves. Recently, we patented a powder formulation for inhalation comprised of lidocaine incorporated in a hydrophilic polymeric matrix of sodium hyaluronate (Lidohyal) delivered by means of a capsule-based dry powder inhaler. <bold>Aim:</bold> To investigate the effects of placebo and Lidohyal inhalation on cough threshold to nebulised distillled water (fog) in humans. <bold>Methods:</bold> In healthy adult subjects, we measured cough threshold (i.e. the lowest concentration of fog capable of evoking at least one cough effort during two distinct challenges) before and after administration of 8 mg Lidohyal or placebo (lactose) inhalation. Changes in pharyngeal sensations, gag reflex, and ECG variables were also noted. <bold>Results:</bold> 9 (3 females) healthy subjects (mean age 45±5 yr) were studied. Median cough threshold values (0.73 ml/min) were unaffected by placebo, but were increased (2.28 ml/min, p < 0.01) by LidoHyal inhalation. In all subjects, cough threshold resumed the control value 60±7 min after Lidohyal administration. The Lidohyal caused a slight, transient unpleasant taste and throat irritation but no chooking on water nor changes in the gag reflex; ECG variables were unaffected by Lidohyal inhalation. <bold>Conclusion:</bold> The Lidohyal could constitute a significant advance in the treatment of cough of any origin for which effective rapid treatment is required.