Abstract

The antitussive activity of a compound on spontaneous (pathological) cough in man must be tested by means of carefully controlled clinical trials. The evaluation may be based on the patients' opinions on the intensity and/or frequency of their cough in successive observations, or their estimation of the therapeutic efficacy

of the treatments being compared (subjective methods). Also, it may be based on the objective observation of the cough variations during the same treatments (objective methods).

The methods used so far have been of the subjective type mainly and are here briefly reviewed. The results of several controlled clinical trials, carried out in order to standardize an efficient technique for estimating the possible antitussive activity of new compounds in man are also reported. In these trials, where codeine was compared with a placebo in old patients, often not very co-operative or with a low I.Q., no significant difference between the two treatments could be found by means of two experimental designs based on subjective methods. On the other hand, a significant difference could be shown by a simple objective method based on the recording of the number of coughs in periods of 3 hours following single administrations of the treatments to be compared. This method proved in repeated experiments to be efficient in discriminating between an active drug and a placebo and may be conveniently employed for the clinical evaluation of new antitussive agents.