A cohort description and analysis of the effect of gabapentin on idiopathic cough.

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Background: Chronic idiopathic cough (known as cough hypersensitivity syndrome) is defined by cough in the absence of an identifiable cause. Gabapentin has been suggested as a treatment but evidence is scarce. The aim of our study was to describe the clinical features of patients with unexplained chronic cough and to investigate the effect of gabapentin (600 mg twice a day for a minimal duration of 4 weeks) in reducing cough symptoms.

Methods: A patient cohort analysis was performed. Patients were retrieved using a query in our medical database for the words 'cough' and 'gabapentin' in 2011. Patients without a clear etiology of cough despite having performed a stepwise diagnostic approach, were included. Medical records of these patients were analyzed. A telephonic survey was performed and patients were asked to retrospectivally rate their cough when they attended the outpatient clinic. They were then asked to rate their cough after treatment with gabapentin. A scale from one to ten was used to score cough severity. They were also questioned about the triggers inducing cough. To evaluate the cough severity score, the results were correlated with questions of the Leicester Cough Questionnaire.

Results: We recruited 51 patients (87% female) with a mean age of onset of 47 years (± 14 y) and an average cough duration of 48 months. The most frequently reported cough triggers included change of temperature (57%), talking (49%) and odours (45%). In 67% of patients, the urge to cough was located in the throat area. Thirty-five patients effectively took the prescribed gabapentin. The average improvement in cough score was 2.8/10 (p<0.0001). Of the 35 patients, 20 achieved improvement of their cough symptoms. Responders had a higher pre-treatment cough severity score (p=0.02) and were more likely to have a history of pre-cough airway infection (p=0.04). Current cough severity score negatively correlated with the Leicester Cough Questionnaire scores (p=0.05).

Conclusion: Chronic idiopathic cough were predominantly middle-aged women, frequently reporting various cough triggers. We also demonstrated that gabapentin can significantly improve cough in these patients. Responders tend to have higher pre-treatment severity scores and have a history of an airway infection.