The February 9, 2002 issue of the British Medical Journal (BMJ) carried an article that reports on the relative ineffectiveness of over the counter cough medications and the total lack of evidence that these common remedies work any better that placebos. The research study reported in the BMJ was designed to determine whether over the counter cough medicines are effective for acute cough in adults.  This study reviewed 15 clinical trials involving 2166 participants involved in randomized controlled trials. 

The results showed that antihistamines seemed to be no better than placebo. There was also conflicting evidence on the effectiveness of antitussives, expectorants, antihistamine-decongestant combinations, and other drug combinations compared with placebo.  This total lack of conclusive evidence lead the researchers to conclude, "Over the counter cough medicines for acute cough cannot be recommended because there is no good evidence for their effectiveness. Even when trials had significant results, the effect sizes were small and of doubtful clinical relevance."