Rationale: Cough is the most common complaint for which medical attention is sought, and chronic cough can be both physically and mentally debilitating. There is currently no evidence supporting the use of antitussives in chronic treatment-resistant cough.
Objectives: We tested the hypothesis that morphine sulfate in the dose of 5 mg twice daily would bring about a reduction in cough frequency and severity in patients failing to respond to specific measures.
Methods: Patients recruited from the Hull Cough Clinic were enrolled into a randomized double-blind placebo-controlled study using 4 weeks of slow-release morphine sulfate and a corresponding period of matched placebo. An open-labeled extension of the core study allowed dose escalation to 10 mg twice daily. Cough was assessed using the Leicester Cough Questionnaire, daily symptom diary, and citric acid cough challenge.
Results: Twenty-seven patients completed the core study. A significant improvement of 3.2 points over baseline was noted on the Leicester Cough Questionnaire (p < 0.01). A rapid and highly significant reduction by 40% in daily cough scores was noted among patients on slow-release morphine sulfate (p < 0.01). Objective testing of the cough reflex using citric acid cough challenge tests did not show any significant changes. Eighteen patients continued into the extension study. Two-thirds of these patients opted to increase the morphine to 10 mg twice daily. At the end of 3 months, there was a similar improvement in cough between the 5- and 10-mg groups.
Conclusion: Morphine sulfate is an effective antitussive in intractable chronic cough at the doses of 5 to 10 mg twice daily.