Lidocaine does a better job of dealing with refractory common cough when delivered as a spray rather than by inhalation, according to new findings. "Our study provides the first randomized-controlled-trial evidence that local anesthetic agents can inhibit chronic coughing when delivered to the throat," Dr. Jaclyn A. Smith of the University of Manchester, U.K., told Reuters Health by email. Chronic cough may affect up to 12% of the population worldwide, Dr. Smith and colleagues note in The Journal of Allergy and Clinical Immunology: In Practice. The condition, defined as cough lasting for more than eight weeks, has a significant impact on health-related quality of life. Many patients report accompanying effects including anxiety, depression, fatigue and sleep disturbance, according to the authors. And, despite extensive investigations and guideline-guided management, a significant proportion of patients with chronic cough remain resistant to treatment of potential triggers such as asthma and gastroesophageal reflux disease. Lidocaine, a non-selective inhibitor of voltage-gated sodium channels, is routinely used topically to reduce coughing during bronchoscopy. A randomized trial showed that spraying the vocal cords and tracheobronchial tree significantly decreased objective cough frequency. A number of case reports and other sources have indicated that nebulized lidocaine may also be of value. To investigate, the researchers conducted a randomized, double-blind, double-dummy, placebo-controlled, three-way crossover study involving 26 subjects with refractory common cough. The effect of single doses of nebulized lidocaine was compared with lidocaine delivered by a throat spray and with matched placebos. Compared with placebo, both lidocaine delivery approaches significantly alleviated urge-to-cough and cough-severity visual analogue scores. In the first hour, the cough rate in placebo patients was 74.2 compared to 31.7 in those who received throat spray and 53.5 in those given nebulized lidocaine. There were few adverse events and all were mild. Over the course of 10 hours after treatment the cough rate with throat spray was 22.6 per hour, significantly lower than that seen with nebulization (26.9 coughs per hour), and with placebo (27.6 coughs per hour). This amounted to a significant reduction of 20% with throat spray and no significant difference between nebulized lidocaine and placebo. The outcome of the study is important, Dr. Smith concluded, "as it suggests the practice of giving inhaled lidocaine through a nebulizer might be ineffective. Also, that this mechanism could lead to valuable treatments if longer-acting agents could be developed with less side effects." GlaxoSmithKline funded the study. Dr. Smith and some of her coauthors report financial ties to the drugmaker. —David Douglas Source
