title: A Randomized Clinical Trial Comparing the Effects of Antitussive Agents on Respiratory Center Output in Patients With Chronic Cough.
abstract: Cough is produced by the same neuronal pool implicated in respiratory rhythm generation, and antitussive drugs acting at the central level, such as opioids, may depress ventilation. Levodropropizine is classified as a nonopioid peripherally acting antitussive drug that acts at the level of airway sensory nerves. However, the lack of a central action by levodropropizine remains to be fully established. We set out to compare the effects of levodropropizine and the opioid antitussive agent dihydrocodeine on the respiratory responses to a conventional CO2rebreathing test in patients with chronic cough of any origin.
  
  
  
  Twenty-four outpatients (aged 39-70 years) with chronic cough were studied. On separate runs, each patient was randomly administered 60 mg levodropropizine, 15 mg dihydrocodeine, or a matching placebo. Subsequently, patients breathed a mixture of 93% oxygen and 7% CO2for 5 min. Fractional end-tidal CO2(Fetco2) and inspiratory minute ventilation (V˙i) were continuously monitored. Changes in breathing pattern variables were also assessed.
  
  
  
  At variance with dihydrocodeine, levodropropizine and placebo did not affect respiratory responses to hypercapnia (P < .01). The ventilatory increases by hypercapnia were mainly accounted for by a rise in the volume components of the breathing pattern.
  
  
  
  The results are consistent with a peripheral action by levodropropizine; the assessment of ventilatory responses to CO2may represent a useful tool to investigate the central respiratory effects of antitussive agents.
  
  
  
  European Union Clinical Trials Register (EudraCT No.: 2013-004735-68); URL: https://www.clinicaltrialsregister.eu/.
authors.affiliation: Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Mannini
authors.affiliation: Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy.
authors.forename: Federico
authors.initials: F
authors.lastname: Lavorini
authors.affiliation: Pneumology Unit, University of Bologna, S. Orsola Malpighi Hospital, Bologna, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Zanasi
authors.affiliation: Medical Department, Dompè SPA, Milan, Italy.
authors.forename: Federico
authors.initials: F
authors.lastname: Saibene
authors.affiliation: Medical Department, Dompè SPA, Milan, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Lanata
authors.affiliation: Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy. Electronic address: giovanni.fontana@unifi.it.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Fontana
mesh_terms: D000328:Adult; D000368:Aged; D000996:Antitussive Agents / Q000494:pharmacology* / Q000627:therapeutic use; D002908:Chronic Disease; D003061:Codeine / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D003371:Cough / Q000188:drug therapy*; D018592:Cross-Over Studies; D005260:Female; D006801:Humans; D006935:Hypercapnia; D008297:Male; D008875:Middle Aged; D011409:Propylene Glycols / Q000494:pharmacology* / Q000627:therapeutic use; D012125:Respiratory Center / Q000187:drug effects*; D012131:Respiratory Insufficiency; D056152:Respiratory Rate / Q000187:drug effects; D016037:Single-Blind Method
chemical_list: D000996:Antitussive Agents; D011409:Propylene Glycols; C014481:dihydrocodeine; C035916:dipropizine; D003061:Codeine
keywords: CO(2) rebreathing; breathing pattern; chronic cough; dihydrocodeine; levodropropizine