Clinical trial examining effectiveness of three cough syrups.

Background: Cough is one of the most common symptoms of respiratory infections for which patients seek relief. This study was done to assess the effectiveness of three commonly prescribed cough syrups.

Methods: In this multipractice, office-based, randomized clinical trial, guaifenesin was compared with guaifenesin plus codeine or guaifenesin plus dextromethorphan in patients with uncomplicated respiratory tract infections. Family physicians enrolled 97 patients between February 1988 and April 1990. Patients were randomly assigned to treatment and were interviewed by telephone at 2, 4, and 10 days to assess cough relief, treatment adherence, and side effects. There were no statistically significant differences among treatment groups at base line.

Results: At day 2 there were no statistically significant differences among treatment groups for any of the outcome measures. At day 4 five of the outcome measures of cough quality, frequency, sleep disturbances, and absenteeism were not statistically significantly different among groups. The only statistically significant difference was the ability to keep up with usual activities, which improved least in patients assigned to dextromethorphan than in patients in other groups. There were no statistically significant differences among the three groups at day 10 for any of the outcomes.

Conclusion: It appears that codeine, dextromethorphan, and guaifenesin are equally effective in relieving cough symptoms.