Antitussive drugs. II. Bronchopulmonary effects of dextromethorphan and doxylamine

Arch Int Pharmacodyn Ther. 1975 Aug;216(2):216-24.


Unlike codeine, dextromethorphan does not cause pulmonary vasoconstiction in the anesthetized dog. The other effects of dextromethorphan are as follwos: a rise in pulmonary resistance indicating bronchoconstriction, and increase in pulmonary blood flow relating to a positive inotropic action, and a decrease in aortic blood pressure resulting from systemic vasodilation. These effects are blocked by previous injections of doxylamine, an antihistaminic drug. This interaction suggests a rationale for the combined use of dextromethorphan and doxylamine in the treatment of upper respiratory infection.

MeSH terms

  • Airway Resistance / drug effects
  • Animals
  • Blood Pressure / drug effects
  • Bronchi / drug effects*
  • Dextromethorphan* / pharmacology
  • Dogs
  • Doxylamine / pharmacology*
  • Drug Interactions
  • Heart Rate / drug effects
  • Levorphanol / analogs & derivatives*
  • Lung / drug effects*
  • Lung Compliance / drug effects
  • Pulmonary Circulation / drug effects
  • Pyridines / pharmacology*
  • Vascular Resistance / drug effects


  • Pyridines
  • Levorphanol
  • Dextromethorphan
  • Doxylamine